Two-stroke performance tuning?

[SS90]

It would be nice to move this in to the "Mainstream" section of this site, and I hope we can do this shortly, however, "Good things take time", and some co-operation is needed.

Let's all get together and start a "Two stroke tuning" thread that rivals others in the world, as, we are all Kiwi's, and as such have an amazing pedagree (particularly when it comes to high powered racing Two stroke engines (Kim Newcome for example, & the often forgotten B.S.L Team, and it's conceptor, Brian Buckley)...........

Looking at the current NZ bucket racing rules, I see the potential for developing a very special type of engine.

A 125cc, Air cooled Two Stroke, limited only by it's capacity, (and), a 24MM carb............

I am unsure of the rules you can apply when starting a thread, but one I would like to place is that no-one is allowed to

"use words bigger than their I.Q"

What I mean is, lets try to simplify it, so that EVERYONE can contribute

......... many effective solutions have been discovered by in-experienced observers, simply because they applied logic that the rest of us missed , because we where "too involved".........

So.... lets Begin......

[SS90]

Since the Japanese started putting "real effort" into Air Cooled 125cc two strokes, it was around the end of the 70's that they gave up, and started to water cool them (and as such, started releasing "real power")

With the current rules in Buckets being the way they are, this gives rise to a "re-emergence" of developmental skills.

The biggest problem facing the 125cc class (air cooled rule not withstanding) is the limitation to a 24mm carb.

Does any-one here have a 125cc air cooled engine they want to develop?

Post the current port timing specs, and "Lets get started!
"

[saxet]

Well I'm looking at building a new Suzy GP125 bucket race motor hence my interest in other threads on K.B. My existing motor is the same thing developed according to John Robinson's specs in a Performance Bike article from the 70's but not taken as far as him. This was my first attempt at tuning a 2 smoke and all in all was pretty successful. Approx 17hp, rideable and very reliable but I'm under no illusions that it's any where current in terms of design. It was based on 70's technology.
I've recently just got an inkling as to how far behind the times it is..still I came 4th in the Bucket GP. As much due to the fact that several of the faster bikes didn't last.
Quite a lesson in reliability vs. power.
Recent reading as led me to the TSS500GP macine developed by Wayne "Wobbly" Wright. a N.Zer engineer for GRand Prix(unsure as to which teams he's worked for).
The porting pics have intrigued me as has the toroidal head.(only just heard about it-Yeah we all have to learn how much we don't know)
I'm guessing some of this could be applied but thats getting many steps ahead of myself.
I suspect some of the bucket tuners have applied some of this as one 50 cc bike seems to have more power than most 100's or 125's.
Will post origina ltiming specs for GP100 motor that I have laying on the bench when I get them sussed(was planning to strat by boring to 125cc but will hold fire for thr moment).Also in the middle of a house renovation project.

Anyone wants basic 2 stroke answers ..I'll do my best.

[Skunk]

I have two (and I've watched TZ350's thread with interest) - one is a cast iron rotary Kawasaki F6 and the other an alloy rotary Suzuki TF125. At present both are in the barely running stage so a little early to post specs. But I will.

[quallman1234]

I have a 100 I'd like to develop. As the chassis is starting to get into shape and has real potential. It is a Highly Ivanised Aprilla RS50 Frame. Sorry Ivan.

Could be a start? Its pretty bog stock. I have access to Lathe's/Mills/everything you can imagine. And some friends who can actually use them accurately and like beer... Well bourbon.
I have two barrels. One completely stock, the other slightly widened by none other than the infamous Ivan Juggins.
Two heads. One what has a slight squish on it. The other bog standard.
One Barrel is stock 50mm the other 0.5OS. Also have a spare new piston kit for the stock barrel.
Its got some old YZ125 chamber donated kindly by Skunk works. With a TZR250 header, welded up by Glen.
The main problem is the 4 speedbox. So i'd need something wide and fat. (The power curve that is). To make the most of what i have.

The biggest gain would obviously be a purpose built chamber, at this stage. But why not do everything at the same time?

Meh, if your specific to a 125. Then thats fine, ill just pod along doing my own thing :).

Admittedly its got no spark atm. But thats minor. I hope.

[tri boy]

Ixion will cream his undies when he stumbles on this thread.:laugh:
(unless he operates commando style)

[saxet]

Hey Quallman1234 probably gonna need the engine model, is it a GP100?. If so you might be lucky, I've got one here I'm planning to bore to 125 but before I do I'll measure it up so there's a base point to start from.....Hopefully within a couple of weeks.

[bucketracer]

Let's all get together and start a "Two stroke tuning" thread that rivals others in the world, as, we are all Kiwi's, and as such have an amazing pedagree (particularly when it comes to high powered racing Two stroke engines (Kim Newcome for example, & the often forgotten B.S.L Team, and it's conceptor, Brian Buckley)...........


I understand TZ350 worked for Bill Buckly at Buckly Systems during the time they were developing the BSL500. If your unsure about anything you could ask him. Just a thought.

[bucketracer]

Hey Quallman1234 probably gonna need the engine model, is it a GP100?. If so you might be lucky, I've got one here I'm planning to bore to 125 but before I do I'll measure it up so there's a base point to start from.....Hopefully within a couple of weeks.

Im working on a GP100 myself, unfortunatly you cant bore a 100 to 125 but you can fit a 125 barrel head piston to a 100 bottom end. They go straight on. The rotary valve and valve cover are a bit different but can be modded. Look at the ESE thread for details.

[bucketracer]

Does any-one here have a 125cc air cooled engine they want to develop?

Post the current port timing specs, and "Lets get started!
"

I have a GP100 but would like to run it as a 125.

Scraped from the ESE thread.

Suzuki GP100/125 Covers and Rotary Valves.

Std. Suzuki GP100 Inlet Opens 135 BTDC Closes 45 ATDC
Ex Opens 94 ATDC Transfers Open 123, 125, 126 ATDC.

Std. Suzuki GP125 Inlet Opens 145 BTDC Closes 55 ATDC
Ex Opens 91 ATDC Transfers Open 122, 122.5, 123 ATDC.

[quallman1234]

Hey Quallman1234 probably gonna need the engine model, is it a GP100?. If so you might be lucky, I've got one here I'm planning to bore to 125 but before I do I'll measure it up so there's a base point to start from.....Hopefully within a couple of weeks.

Hey its an AX100 (yea yea i know).
3 petal reed valve. Standard.
I have a 6 petal reed valve sitting around. A V-type reed valve. Could mod it and make it fit.

First Question of the day! What advantages and Disadavantage's are there with larger reed blocks?

p.s
Its' kyle the kid who lent you a back protector :) at taupo.

[saxet]

Hey Kyle

With Bigger reed blocks I'd say..advantages-more fuel/airflow.
Disadvantages-too peaky-too much fuel.
So far I've learnt everything is a comprimise and finding the limit where comprimise becomes liability is the trick.

If I'm off track someone say so.

[SS90]

The more the merrier!

With the Ax100, there is a small problem with tuning, well, that is, they look like "crankcase induction" (like Mb100's, CR125's etc for example), but the reed block location ends up making quite a torturous path through a "piston window", like say an RZ250 (except the RZ intake is mounted directly on the cylinder, and far better in this respect!)

The intake rout is fairly poorly designed (in as much as performance goes), and it could perhaps be considered wise to simply "go bigger" (and try and develop your intake system to simply "flow more", to help compensate for this...........

Personally, with out having one in front of me, it's difficult to say, BUT, I think it may actually be a good idea (in this case), and some good gains could be made!

Does anyone know of an AX100 with a bigger reedblock fitted?

Also do you have the cylinder off the engine?

I found these pictures, so you can see what I mean about the inlet.

[SS90]

Well I'm looking at building a new Suzy GP125 bucket race motor hence my interest in other threads on K.B. My existing motor is the same thing developed according to John Robinson's specs in a Performance Bike article from the 70's but not taken as far as him. This was my first attempt at tuning a 2 smoke and all in all was pretty successful. Approx 17hp, rideable and very reliable but I'm under no illusions that it's any where current in terms of design. It was based on 70's technology.
I've recently just got an inkling as to how far behind the times it is..still I came 4th in the Bucket GP. As much due to the fact that several of the faster bikes didn't last.
Quite a lesson in reliability vs. power.
Recent reading as led me to the TSS500GP macine developed by Wayne "Wobbly" Wright. a N.Zer engineer for GRand Prix(unsure as to which teams he's worked for).
The porting pics have intrigued me as has the toroidal head.(only just heard about it-Yeah we all have to learn how much we don't know)
I'm guessing some of this could be applied but thats getting many steps ahead of myself.
I suspect some of the bucket tuners have applied some of this as one 50 cc bike seems to have more power than most 100's or 125's.
Will post origina ltiming specs for GP100 motor that I have laying on the bench when I get them sussed(was planning to strat by boring to 125cc but will hold fire for thr moment).Also in the middle of a house renovation project.

Anyone wants basic 2 stroke answers ..I'll do my best.

Cool!

does anyone have some dyno curves available for, say, a tuned Gp125 (or similar)
It doesn't have to be a GP125 as such, but a competitive disc valved air cooled two stroke with a 24mm carb to see what can be done

I see that Suzuki only claim 9.5 P.S, originally and I cannot find a curve for a tuned one.

I am interested to see what sort of power they are making with 24mm carb...... I think that 17 P.S would be heading towards the most you would see.....but I truly don't know!

[quallman1234]

The more the merrier!
Does anyone know of an AX100 with a bigger reedblock fitted?

Also do you have the cylinder off the engine?

I found these pictures, so you can see what I mean about the inlet.

Skunk's has a bigger reedblock fitted :).

Yes i know what you mean about the inlet.
Its going to be difficult getting a v-type reed block in there as well.
Might have to move the reedblock back. What would this effect?

[F5 Dave]

. . .
The porting pics have intrigued me as has the toroidal head.(only just heard about it-Yeah we all have to learn how much we don't know)
I'm guessing some of this could be applied but thats getting many steps ahead of myself.
I suspect some of the bucket tuners have applied some of this as one 50 cc bike seems to have more power than most 100's or 125's.
. . .

My 50 doesn’t need such a head, in fact the sparkplug would be clouted by the piston if so. Bigger the cylinder the more this sort of thing is applicable. Might experiment machining up some domes for my Trinity 496 (essentially 250cc cylinders) in the future . . . –if I ever feel like it is wanting more that 100hp of course.


The more the merrier!

With the Ax100, there is a small problem with tuning, well, that is, they look like "crankcase induction" (like Mb100's, CR125's etc for example), but the reed block location ends up making quite a torturous path through a "piston window", like say an RZ250 (except the RZ intake is mounted directly on the cylinder, and far better in this respect!)

The intake rout is fairly poorly designed (in as much as performance goes), and it could perhaps be considered wise to simply "go bigger" (and try and develop your intake system to simply "flow more", to help compensate for this...........

Personally, with out having one in front of me, it's difficult to say, BUT, I think it may actually be a good idea (in this case), and some good gains could be made!

Does anyone know of an AX100 with a bigger reedblock fitted?

Also do you have the cylinder off the engine?

I found these pictures, so you can see what I mean about the inlet.

Yeah the AX has a weird set up with a reedblock (on bottom of barrel not shown) like an ancient RM (and incidentally my 50) but with no piston ports. Really I have to wonder about developing an AX further due to it’s odd gearbox, however didn’t know there was a 125 version.

[Buckets4Me]

122464



hows that for a start
an rs gp :drool:

[Skunk]

Skunk's has a bigger reedblock fitted :).Um, no. Just different.


With the Ax100, there is a small problem with tuning, well, that is, they look like "crankcase induction" (like Mb100's, CR125's etc for example), but the reed block location ends up making quite a torturous path through a "piston window"Not quite. No piston port - just the reeds. But yeah, crap inlet path.


Yeah the AX has a weird set up with a reedblock (on bottom of barrel not shown) like an ancient RM (and incidentally my 50) but with no piston ports. Really I have to wonder about developing an AX further due to it’s odd gearbox, however didn’t know there was a 125 version.Never heard of one - and I've looked! 4 speed box is a handicap but the selector set-up is shit. Don't waste time even spending a cent on one of these. Seriously.

[saxet]

Hey its an AX100 (yea yea i know).
3 petal reed valve. Standard.

Hate to say it but Skunks got more right to know than most of us.The very basics -If it hasn't been geared down start there. I have found on 5 speeders 1 tooth smaller on the front is a good start if you havn't already.I don't get into top at Slipway or Kaitoke.


[QUOTE=F5 Dave;1979301]My 50 doesn’t need such a head, in fact the sparkplug would be clouted by the piston if so. Bigger the cylinder the more this sort of thing is applicable. Might experiment machining up some domes for my Trinity 496 (essentially 250cc cylinders) in the future . . . –if I ever feel like it is wanting more that 100hp of course.

Don't claim to know whats been done to it but it and you are seriously quick.

[QUOTE=Buckets4Me;1979347]122464



hows that for a start
an rs gp :drool:

I like the look of that. It's what I'd like to get near with the next motor. As Ive Little experience I'm trying to cheat a bit and avoid some of the trial and error others have had to go thru.. Yeah lazy.

[Buckets4Me]

I'm trying to cheat a bit .. Yeah lazy.

nothing wrong with cheating and being lazy :dodge:
:buggerd: :lol:

[SS90]

Skunk's has a bigger reedblock fitted :).

Yes i know what you mean about the inlet.
Its going to be difficult getting a v-type reed block in there as well.
Might have to move the reedblock back. What would this effect?

It's a really good question, and it touches on a very complex part of the two stroke engine.

In order to keep it simple, I'll try to be quite general!

Basically, a longer inlet manifold will tend towards developing more "bottom" end power (at the cost of "top end power"), and a shorter on is the opposite (more top, less bottom)

It is quite complicated to calculate correct two stroke inlet manifold lengths (due to the fact that in a two stroke the crankcase volume (which changes with each piston stroke) is included in the calculation of a two stroke manifold length.

As such, the accepted method seems to be "try it and see".

Some rules remain constant though, and the most important is ...

Do not put the reed block too close to the piston (this will upset mixture strength, and make jetting near impossible, as well as reduce the "useable rpm's" of the engine (basically, the engine won't rev out)

Too far, and the symptoms are almost the same, but you will get the jetting set acceptably, but it won't rev much at all (less that too close in my experience).

Some logic applies here, and basically, if it looks too far away, it probably is!

I would suggest at aiming to have the reed block tips 15-20mm away from the liner window.



If you are really keen on this idea, I think it would be wise to go to the effort of completely redesigning the inlet, system....it is clear some improvements could be made there!

I have never tuned an AX100, but had one as a bucket (standard) for my first bucket.

Like F5 Dave said, the 4 speed might start to hinder development though!

[SS90]

122464



hows that for a start
an rs gp :drool:

Mate, thanks for that!

Do you know what specs the engine had (i.e, what size is the carb, is it air cooled)

[SS90]

[QUOTE=F5 Dave;1979301]My 50 doesn’t need such a head, in fact the sparkplug would be clouted by the piston if so. Bigger the cylinder the more this sort of thing is applicable. Might experiment machining up some domes for my Trinity 496 (essentially 250cc cylinders) in the future . . . –if I ever feel like it is wanting more that 100hp of course.



I agree with that one. It's debatable if such a head would have any effect on a 125 bucket (with a small carb)...... I have no experience with such a head in such a situation, but I think, from what I see and read, if you are in a situation where the level of tuning is so high, that everything starts to count, this design is of significant benifit.

Like Dave said, he has 100 HP (his trinity engine creation) and some other tuners have 112 or so..... and it seems it takes expensive carbs, pipes, ignitions and heads to make the extra power..... I would be interested to see what the power was with the same extras added, but using the original Trinity heads.....

[F5 Dave]

Numbers are just numbers without the same reference (ie dyno) There is another local dyno that would read it at 115 (and a further one reputed to be more optimistic), my only runs were with totally wrong needles so I could only pull dirty until near peak revs & ran out of jets in the session so I was running 2 sizes too rich in one side, probably right in the other. I choose the path of smaller carbs and low compression for a roadbike on pumpgas. A race engine could pull waay more + add a few revs to boot.

B4me that curve looks real friendly. What type of dyno was that one? Presumably this is since Taupo 'cause it didn't seem anywhere as fast then.

[saxet]

[QUOTE=quallman1234;1977942]Hey its an AX100 (yea yea i know).
3 petal reed valve. Standard.

I can't help thinking that this could be an interesting design experiment but as it's a 4 speed, it's gonna reach it's limits quickly.
In any tuned engine there is a tend ency for power to be concentrated further up the power range.This is where the 4 speed falls down e.g. the gaps between gears can be too big. If, as standard the engine has say a 4thousand useable rev range, after tuning work that may drop to 3 thou useable rev range so when you change up a gear the revs in the next gear drop below this useable rev range.
This is one reason that tuners try to get as much power out of an engine while trying to keep the power spread as wide as possible.
Lowering gearing can help here but a 4 speed is more limited in this respect.

[Buckets4Me]

B4me that curve looks real friendly. What type of dyno was that one? Presumably this is since Taupo 'cause it didn't seem anywhere as fast then.

At Taupo the end of the chamber fell of :lol:
the bike is as fast if not faster in a straight line than the one that won the gp but the rider is not.
also I tend to run the main jet a size or 2 too big I know I know but I use to lend the bike out a lot
and I know other people ride it harder than I and I'm not keen on them leaning it out and destroying it
so I play safe

at the 2 hour it was clocked at 30 sec 1 rider and 31 the other in the shoot out
finished 3rd after being droped 3 times and was running faster than 30 sec at one point

but as you say not all dynos are equal and I wouldn't put to much faith into the graph either

[SS90]

[QUOTE=quallman1234;1977942]Hey its an AX100 (yea yea i know).
3 petal reed valve. Standard.

I can't help thinking that this could be an interesting design experiment but as it's a 4 speed, it's gonna reach it's limits quickly.
In any tuned engine there is a tend ency for power to be concentrated further up the power range.This is where the 4 speed falls down e.g. the gaps between gears can be too big. If, as standard the engine has say a 4thousand useable rev range, after tuning work that may drop to 3 thou useable rev range so when you change up a gear the revs in the next gear drop below this useable rev range.
This is one reason that tuners try to get as much power out of an engine while trying to keep the power spread as wide as possible.
Lowering gearing can help here but a 4 speed is more limited in this respect.

I agree 100% with the idea that it will be an interesting design experiment, and, with some careful attention to port timing, and some attention to basics you would end up with a very rideable machine (with good low down torque), which, what we always forget, is what a two stroke is very good at!

The engines I work on are only four speed and if you build one with good peak horsepower, the first question an experienced observer will ask is "does it pull 4th", as the ratio from 3rd to 4th is quite far, it can be a problem!

The points about Dyno's and comparisons are valid (I am lucky to operate a very high quality one, that does not vary from shop to shop like some other brands)

As we all know, correction factors are subject to inaccuracies and good software is as important as good components (and experienced operators when it comes to a dyno)

But, apples to apples, oranges to oranges.

But if use the same dyno when developing, no matter what the number, a gain is a gain!

[Skunk]

My exhaust port timing on the AX100 is 189°. The inlet has been tidied, as have the transfers, but I don't know the timings.

[SS90]

My exhaust port timing on the AX100 is 189°. The inlet has been tidied, as have the transfers, but I don't know the timings.

Great start!

There is quite a bit of information you need when you are dealing with two stroke ports (when they start to open, how long they are open for, when they close, etc.....)

It seems quite daunting when you first start to look at it, and this is compounded by some internet based information, that can be not only confusing, but also incorrect!

To measure the timings, the only special tools you really need are a timing wheel, and a dial test indicator.

Some people also use feeler guages (to determine when a port closes, but I tend to use a torch to shine a light through the port....when the light stops shining through the port, the port is closed), but that is an individual preference in my opinion.


These tools are not too hard (or expensive to obtain), and can often be borrowed.

Maybe this could be a good topic for discussion......How to measure your port timings!

[koba]

Just for general interest I measures the a100 exhaust duration at 165 dregrees, but it was done quickly and without the proper gear so it may be a wee bit off.

[Buckets4Me]

so whats happining with these other 2 stroke engines

havent heard any news lately ????

[Skunk]

so whats happining with these other 2 stroke engines

havent heard any news lately ????
I'm taking measurements of my new engine and then I'll decide where to go with the timings. At the moment it's looking like a 3mm base gasket will be a good start. Then I can tidy the head shape a bit to bring the compression back and improve the squish. I'm also researching doing away with squish...

[TZ350]

My exhaust port timing on the AX100 is 189°. The inlet has been tidied, as have the transfers, but I don't know the timings.

If the exhaust is 189 duration then it opens 85.5 degrees ATDC.

Thats (360 - 189)/2 = 85.5 Degrees After Top Dead Center.

.

[TZ350]

I'm taking measurements of my new engine and then I'll decide where to go with the timings. At the moment it's looking like a 3mm base gasket will be a good start.....

Hi Skunk, if your going to make a 3mm base gasket you could try making a super big one so it sticks out the sides, that way you can pick up some extra fin area. On my bike I found there was a lot of heat under the barrel in the area of the exhaust port. The base gasket/fin could be made from copper or aluminium.

.

[TZ350]

Then I can tidy the head shape a bit to bring the compression back and improve the squish. I'm also researching doing away with squish...

My recent experiance with squish and ignition timing is that the non-squish heads required much more advance than the squish head that had an effective squish band.

I expect the difference is in the greater mean squish velocity MSV of the squish head which basically stirs the burning mixture up and that speeds the combustion process.

Optomised (using a dyno) ignition timing and a faster burn means less negative pressure on the piston BTDC. But every thing is a compromise though, and if you go with the open chamber non-squish option please let me know why you think that should be better. Thanks.

.

[Skunk]

If the exhaust is 189 duration then it opens 85.5 degrees ATDC.

Thats (360 - 189)/2 = 85.5 Degrees After Top Dead Center.

.
That's the old AX100 engine specs. It's last outing was at the Easter GP.

I have a TF125 in the bike now. Std except for matching and cases etc and tiding things up. A rough measure shows the exhaust at 144° - a 3mm base gasket would give 188°. I've yet to triple check my measurements...

With the non squish head I'd expect 91 to be the better fuel as I believe it burns quicker.

[TZ350]

With the non squish head I'd expect 91 to be the better fuel as I believe it burns quicker.

Looking into the burn rate of 91, 96, 98 Etc is something we plan to do too. They say you don't get "more power" from the fuel itself but we hope to make gains from being able to retard the ignition and reduce the negative work done on the piston.

From what I’ve been reading it seems that people generally think that the higher the octane the slower the fuel burns but this is mostly not true with American performance fuels.

But closer to home, it's true that Av Gas is not a fast burn fuel or even a good burn fuel, its just a reliable burn fuel for slow reving air cooled aircraft engines who's cylinder head temperatures can very a great deal.

A mix like F5 uses of leaded Av Gas and unleaded, could be a good idea though.

.

[TZ350]

a 3mm base gasket would give 188°. I've yet to triple check my measurements...

When Thomas set our engines up, he used a degree wheel, found TDC and then packed the cylinder up a bit at a time until the transfer ports opened at the required point. The thickness of the packing was the amount he had to take off the top of the barrel. Then he measured how much he had to raise the exhaust and lower the inlet.

Thomas finds the inlet opening position then marks the piston skirt through the inlet port. This gives him an idea of how much he can cut off of the piston skirt and/or lower the inlet port floor. Thomas says a low wide port fills the crankcase better than a tall narrow one of the same area.

Interesting info about maintaining port velocity:- http://www.gofastnews.com/board/technical-articles/1130-porting-school-7-power-port-volumes.html

The inlet port needs to have much the same area as the carb. And he likes to strike a compromise with port height to width, so he can cut something off of the piston skirt so that the piston clears the top of the inlet port around TDC for 30-50 degrees or so. This gives the inlet a dwell period where the inlet is fully open for a time, the more the better he says.

.

[SS90]

I'm also researching doing away with squish...

That is a really good idea Skunk (in my opinion)....the TYPE (i.e useable spread) of power you are looking for on a 4 speed transmission is quite different to what you would be looking for with a close ratio (6 speed) (or,like Cagiva did with one of their Mito road 125's 7 speed!) gear box.

Using a "squish band" head will typically give a "peakier" power delivery (although it will indeed give a higher "peak power" result).... in the same way that having large exhaust port duration will.

Sure, that "squish band" head will make more power, it just places that extra power in a narrower RPM range. My opinion is that, in the case of a compromised set of available gear ratios (4 speed) this is not ideal.

My experience with non squish heads has been that, like Teezee says, non squish heads require less retard, but more so with a "squish" head the ignition map used needs to be very well controlled (to suit the pipe design as as well), whereas, the non "squish" head shows more "real world" gains using only very basic ignitions (early "twist and go" scooters are a good example) that have between 8 to 12 degrees retard from static. (the amount depends on what coil/CDI you use.....), but typically, the older stuff is either 8 or 12 degrees.

In my opinion, pretty good for an (essentially) low revving engine.

Teezee also gave some good examples in the ESE thread on how SMALL the power gain was between his "highly tuned" bucket (central spark plugged "SQUISH BAND" head, high port timing,modified inlet disc etc), compared to other GP125 engines with the same exhaust, standard heads (i.e, NO SQUISH BAND), slightly raised cylinder compression, and standard exhaust port/inlet disc etc)

I think the peak power was the same (eventually), and the less tuned ones made a wider spread of power (from memory.....)

I have seen ignition maps for modern high revving racing two stroke engines (revving to say 14,000) that range from 30 deg BTDC (at 1,500 RPM to MINUS 2 Deg ATDC (at 13500 RPM).........

These engines (naturally) have "squish band" heads.....as well as 6 speed close ratio gear boxes.........

There are road going two strokes that have curves similar to the last example as well.............



However, if, like your Bucket, you have less gear ratios available (4 speed), then some compromises must be made.

If you want to start with using a different type of head design to what others are using (in buckets anyway), you will however, find that (with careful attention to other areas of your tuning) (correct primary and cylinder compression, correct ignition (type and design) porting layout and exhaust) you will make almost the same as other "high port" tuned engines, but with a longer spread of power, and more Torque.

The figure you have posted (for the duration of the exhaust) is very much where I would suggest a 4 speed air cooled 125 would want to be (What primary gear ratio do you have?)

what ideas do you have for the duration of the transfers..... (I like 131...(just as a number;))

However, like as been said before, it is silly to just throw around port timings, but with the set up you have (4 speed gear box) there are a few constants......

Oh, also (when you have the time) could you measure the distance from the top the piston to the top of the cylinder (measured when the piston has JUST closed the exhaust port) and post that as well?

If it is not too much to ask, would you also be able to post a picture of the combustion chamber of your cylinder head, as well as a picture of the crown of the piston you will be using?

I personally believe that while the intake area of an AX100 is quite complicated, you should be able to have a good tourqey engine despite this "set back"!

[SS90]

Hi Skunk, if your going to make a 3mm base gasket you could try making a super big one so it sticks out the sides, that way you can pick up some extra fin area. On my bike I found there was a lot of heat under the barrel in the area of the exhaust port. The base gasket/fin could be made from copper or aluminium.

.

By all means if you think that will give you some gains (wider spacer) do it Skunk, but personally I have never seen any data to support the notion that such a design gives any tangable gains whatsoever.

There are plenty of Two stroke air cooled buckets racing in New Zealand putting out in excess of 21 Horsepower, and I am still to hear of one that has a spacer like that.

[TZ350]

we need to examine the impact the combustion chamber has on an engine.

Abnormal combustion, better known as detonation, is more likely with a slow combustion process since it allows time for an additional flame front to start.

And a combustion chamber that has a fast burn rate is essential to increase the engine's octane tolerance.

Air cooled Suzuki motor X bikes that I have had a look at, all had open combustion chambers without any squish and about 22 RWHP. Kawasaki and Yamaha much the same but with squish bands. But the Suzuki was known for the width of its power band.

The jury is still out in our camp over squish/non-squish heads for our buckets.

But it is remarkable the difference it made to the ignition timing requirements of our bikes.

We can see from the ignition timing requirements the difference in burn rates between the open and squish type combustion chambers on our bikes.

I am hoping to get my bike with the squish chamber to Henderson Yamaha's dyno so I can get a printed dyno sheet so we can compare the torqe curves to the other non squish engines.

An interesting artical on combustion chamber shape:-

http://www.highperformancepontiac.com/tech/0209hpp_engine_combustion_chamber/index.html

[TerraRoot]

I'm gonna take a stab at this. don't bite.
You mention that turbulence needs to be intrduced in the combustion event, I belive that with a non squishbanded head what is suposed to happen is the scavagne loop is still going with the piston at TDC

SO.. with crap transfers that dont make much of a loop go with squish
With damn good high reving well angled multiple transfer ports it's a waste of time to squish the mixture since it's all ready moving quite fast ina loop.

do i make sense?

[SS90]

I'm gonna take a stab at this. don't bite.
You mention that turbulence needs to be intrduced in the combustion event, I belive that with a non squishbanded head what is suposed to happen is the scavagne loop is still going with the piston at TDC

SO.. with crap transfers that dont make much of a loop go with squish
With damn good high reving well angled multiple transfer ports it's a waste of time to squish the mixture since it's all ready moving quite fast ina loop.

do i make sense?

Sounds logical to me Terraroot!;)

Now, following along those lines, if you have a 4 speed transmission, it would be logical to suggest that "overrev" is required for high speed gear changes........ it has been established that a retarding ignition will help this, but, what is your opinion on cylinder compression ratios, (and their effect on overrev?)

skunks Ax100R is limited by that 4 speed transmission, but carb size is open....... (hmmmmmm)

Sounds like a small frame Vespa to me!:Punk:

[TerraRoot]

Damn! bitten off more then i can chew! I think maybe lower (primary right?) compression ratio and I hazard a guess that the mixture just needs space to be turbulent in. The more mixture packed into the crankcase before the reed closes seems more important than the primary compression.

Also you bring up something that's being annoying me, where the heck do people get an adjustable cdi for a 6v single cylinder two stroke? 3d or 2d?

[TZ350]

A MacDizy Engine Rebuild with Photos:- http://www.macdizzy.com/1989hhopup.htm

.

[TerraRoot]

macdizzy's used to be a great place, anyone else mourn the board's there going commercial?

RE cdi's: Megajolt won't work on 6v, http://home.earthlink.net/~jcgebhart/megaignite.html i'd efi the lot if i could sort it to run on 6v. off to indian ebay for 12v system off a late rx135 :crybaby: need more money

[Yow Ling]

Also you bring up something that's being annoying me, where the heck do people get an adjustable cdi for a 6v single cylinder two stroke? 3d or 2d?

www.zeeltronic.com has fully programmable cdi's about 100 euros , I have one on my LC and it is great

[TZ350]

That is a really good idea Skunk (in my opinion)....the TYPE (i.e useable spread) of power you are looking for on a 4 speed transmission is quite different to what you would be looking for with a close ratio (6 speed) (or,like Cagiva did with one of their Mito road 125's 7 speed!) gear box.

Screen Scrape:-

"You may be interested to know, that in many cases a non-squish combustion chamber, with its complete utilization of the mixture to offset the power-limiting effects of a necessarily-lower compression ratio, has proven to be best in absolute terms of power and economy."

Read it all here:- http://toostroke.blogspot.com/2007/12/squish-bands.html

"Our application here, of course, is strongly biased toward maximum horsepower, and that points toward a squish-band head - which is what you will have in most motorcycles in any case. I will warn you, now, that it may be unwise to follow the old-time tuner's habit of increasing an engine's compression ratio as an opening gambit in the quest for better performance. Indeed, before your work is done you may find it necessary to reduce your engine's compression ratio below the stock specification. You see, in the final analysis it is not so much compression ratio as combustion chamber pressure that determines the limit - and these are not at all the same things."

So its a trade off between broad power and maximum horsepower.

.

[SS90]

Also you bring up something that's being annoying me, where the heck do people get an adjustable cdi for a 6v single cylinder two stroke? 3d or 2d?

You had me up to here........

Pardon?

[SS90]

Screen Scrape:-

"You may be interested to know, that in many cases a non-squish combustion chamber, with its complete utilization of the mixture to offset the power-limiting effects of a necessarily-lower compression ratio, has proven to be best in absolute terms of power and economy."

Read it all here:- http://toostroke.blogspot.com/2007/12/squish-bands.html

"Our application here, of course, is strongly biased toward maximum horsepower, and that points toward a squish-band head - which is what you will have in most motorcycles in any case. I will warn you, now, that it may be unwise to follow the old-time tuner's habit of increasing an engine's compression ratio as an opening gambit in the quest for better performance. Indeed, before your work is done you may find it necessary to reduce your engine's compression ratio below the stock specification. You see, in the final analysis it is not so much compression ratio as combustion chamber pressure that determines the limit - and these are not at all the same things."

So its a trade off between broad power and maximum horsepower.

.

Well..... screw me sideways......

[bucketracer]

Its good to see TZ backing up what SS90 and Thomas have to say by referencing other material that supports them.

Your a good sport TZ, thanks for all the real info and extra reading that goes with your intelligent input.

.

[Skunk]

That is a really good idea Skunk (in my opinion)....the TYPE (i.e useable spread) of power you are looking for on a 4 speed transmission...
Actually it's now a 6 speed box. TF/TS125. TF has a crap 1st - 2nd ratio so effectively a 5 speed...

The figure you have posted (for the duration of the exhaust) is very much where I would suggest a 4 speed air cooled 125 would want to be (What primary gear ratio do you have?)
As you missed the bit earlier about it being a new engine I have to ask which timing you're asking about. The TF or the AX?


what ideas do you have for the duration of the transfers..... (I like 131...(just as a number;))
Haven't calculated that yet. Ballpark is in that region though.


Oh, also (when you have the time) could you measure the distance from the top the piston to the top of the cylinder (measured when the piston has JUST closed the exhaust port) and post that as well?30mm.


skunks Ax100R is limited by that 4 speed transmission, but carb size is open....... (hmmmmmm)Carb is restricted now. I'll be paying careful attention to the volume of the intake path...


"You may be interested to know, that in many cases a non-squish combustion chamber, with its complete utilization of the mixture to offset the power-limiting effects of a necessarily-lower compression ratio, has proven to be best in absolute terms of power and economy."

Read it all here:- http://toostroke.blogspot.com/2007/12/squish-bands.html
So its a trade off between broad power and maximum horsepower.
Broad power is my aim - I don't give a rats about peak power.

[TerraRoot]

thanks yow ling, it's nice but seems to need a 12v supply :( and it seems like it's only 2d, a fully mapped 3d ignition curve should produce a much softer engine still with good power.

Any one have some thoughs on EFI?
http://www.rzrd500.com/phpBB2/viewtopic.php?t=1795&highlight=efi+rz350
http://www.rzrd500.com/phpBB2/viewtopic.php?t=1899&highlight=efi+rz350

you could run a massive intake and it would still be driveable everywhere.

[SS90]

Hi thought you may be interested in this cylinder skunk.

I's called an ML1, by a small tuning company called Quattrini.

(They don't have a website, it's just a small group of guys from an area in Italy called "Parma", kind of a "Holy Grail" for 2 stroke tuners in Italy.)

The layout is based on a Kart sport engine (originally, although I am unsure which one), and as such it is quite a revvy cylinder, accordingly you have to run a primary gear ratio of 2.86 or 3.00 (which is quite low really)

I am hoping to get 25 PS and 18 NM from this cylinder, (They have 17 PS and 15NM "plug and play", and are quite "peaky"...but I am currently unsure why that is!)

I am suspecting that is because the ones I have tested on the dyno have all had primary compression ratios set "old school" (too high), with unsuitable (again "old school") expansion chambers, as the port layout and scavenge patterns look alright to me.

The exhaust/ transfer durations are 183 deg and 128 deg (according to the information I have been given, but I will measure that, as I suspect they a bit longer than that.

I also believe you could go a few degrees higher on the exhaust (if those specs are correct)

I read somewhere that you made your own exhaust, are you intending to use that on your new engine, or make a new one?

[speedpro]

you could run a massive intake and it would still be driveable everywhere.

That's the theory anyway, as far as fueling goes. There's a bit more to it.

[Chambers]

The exhaust/ transfer durations are 183 deg and 128 deg (according to the information I have been given, but I will measure that, as I suspect they are a bit longer than that. I also believe you could go a few degrees higher on the exhaust (if those specs are correct)

Exhaust Duration of 183 = Ex Opens 88.5 ATDC and Transfer Duration of 128 = Trans Opens 116 ATDC.

"you could go a few degrees higher"

Ex Opens 86.5 and Trans Opens 116 ATDC.

With more upswept 24-30 deg main transfers, shallower secondaries 10-15 deg, 55 deg boost and a pipe with a long shallow first diffuser section seems to be pretty much where current port timing is for bikes with a useable power spread.

On a piston port motor, inlet ports that are to big lose velocity and therefor inertia and can wind up with less air in the crank case than there would have been had the mixture stream had enough inertial push to thoroughly pack the crankcase as the piston closes the inlet port.

The reed valve cylinder that SS90 has shown us is a very good looking piece of work. Its very big inlet is possibly why the cylinder requires a bigger crankcase volume as the inlet stream may lack velocity and inertia to propery fill a tighter volume. This cylinder looks like it benifits from a pipes ability to draw mixture through the crankcase.

.

[Skunk]

Hi thought you may be interested in this cylinder skunk.I read somewhere that you made your own exhaust, are you intending to use that on your new engine, or make a new one?I did. It was an attempt to tame the power delivery. I'll make a new one when I sort the new engine.
Attached are a couple of crappy pics of the TF125 bits. I've been busy helping prep a KR150 and a GSXR600K4 for next weekend, so nothing of mine has been looked at.:pinch:

These pics are standard TF. I'm still in the planning/learning/theory stage.

[SS90]

Exhaust Duration of 183 = Ex Opens 88.5 ATDC and Transfer Duration of 128 = Trans Opens 116 ATDC.

"you could go a few degrees higher"

Ex Opens 86.5 and Trans Opens 116 ATDC.

With more upswept 24-30 deg main transfers, shallower secondaries 10-15 deg, 55 deg boost and a pipe with a long shallow first diffuser section seems to be pretty much where current port timing is for bikes with a useable power spread.

On a piston port motor, inlet ports that are to big lose velocity and therefor inertia and can wind up with less air in the crank case than there would have been had the mixture stream had enough inertial push to thoroughly pack the crankcase as the piston closes the inlet port.

The reed valve cylinder that SS90 has shown us is a very good looking piece of work. Its very big inlet is possibly why the cylinder requires a bigger crankcase volume as the inlet stream may lack velocity and inertia to propery fill a tighter volume. This cylinder looks like it benifits from a pipes ability to draw mixture through the crankcase.

.

Yes, this one will be an interesting project.

The manufacturer, while they have taken Kartsport technology, and adapted it (well), in my opinion, they have not really spent the time to correctly develop the set up. (they recommend, like I say a primary drive gear ratio of 3.00), as well as a primary compression ratio of over 1.5:1.

Obviously I will be going lower than that (the primary compression), quite a bit actually, due to the specifics of this cylinder (as well as the design of the new exhaust)

I will put a figure on the ratio I use, so we can all have useable data for the future.

We all know 1.5:1 is the maximum, but as such, there will be a minimum value as well (I don't know what that is yet, and have never seen any data to say what the minimum is) it would be nice to have a value. (using modern expansion chamber designs)

Mush like Chambers has suggested.

The engines I have seen set up like this, have all (4 in total) had the same power (17 PS and 15 NM), which has always been dissapointing. However, all the engines of this type I have had on the dyno have not been built by experienced tuners, so I suspect that has a large part to play.

Last year I fitted one of my/our exhausts to one of such set ups (no other changes) and one made 3 PS more instantly.

I can honestly say that that particular exhaust design is 2 year old technology.

I have spoken to other people over here, and 2 others have been able to get 25 PS (with quite alot of work) I am hoping to get similar results with less work ( actually none on the cylinder).
I believe that this is a good example of a cylinder that NEEDS as much modern set up as can be managed.

For this cylinder, there is only one (specific) exhaust available (see attachment), and, it really is not very good.

It's an "old tech" design, and not really very impressive with it's results.

A friend of mine (who works for Huskvarna) is designing an exhaust specifically for this cylinder (using up to date calculations), and the whole engine will be set up to specs using ideas we have spoken about on this and other threads.

I will use this engine to collect data for that exhaust as well.

The customer is adamant we use the exsisting "squish head" though...... so that is the only thing I don't like. (but the squish area is a little different to others, and could be considered quite modern thinking)

[SS90]

I did. It was an attempt to tame the power delivery. I'll make a new one when I sort the new engine.
Attached are a couple of crappy pics of the TF125 bits. I've been busy helping prep a KR150 and a GSXR600K4 for next weekend, so nothing of mine has been looked at.:pinch:

These pics are standard TF. I'm still in the planning/learning/theory stage.

Cool!

I know how hard it is to find time to work on your own stuff skunk!

What are your current thoughts/opinions on cylinder heads? (and squish/non squish)

[Skunk]

Cool!

I know how hard it is to find time to work on your own stuff skunk!

What are your current thoughts/opinions on cylinder heads? (and squish/non squish)
Ummm, I'm so new that I haven't enrolled in a school yet... To call me a beginner at engine work is way too generous.
The ESE engine thread is what encouraged me to give it a go and taught me what boost and transfers are!
Don't ask me for my opinion yet, I'm very much reading and trying to comprehend it all.
So far I've decided (probably) on a non-squish head and about 188° exhaust.
The rest I'm still mulling over and researching what will go best with that for my engine.
On top of that I have the option of piston port and reed (as it is) or going full piston port or full reed. Hence the long discovery process. There are many things I need to check and measure before I make any decision; and that will be passed by a few people for their input too.
The worst thing for me is everything seems to look at maximum power rather than maximum duration of power (which is my aim).

I have plenty of time and no resources, so don't wait up!

[SS90]

Ummm, I'm so new that I haven't enrolled in a school yet... To call me a beginner at engine work is way too generous.
The ESE engine thread is what encouraged me to give it a go and taught me what boost and transfers are!
Don't ask me for my opinion yet, I'm very much reading and trying to comprehend it all.
So far I've decided (probably) on a non-squish head and about 188° exhaust.
The rest I'm still mulling over and researching what will go best with that for my engine.
On top of that I have the option of piston port and reed (as it is) or going full piston port or full reed. Hence the long discovery process. There are many things I need to check and measure before I make any decision; and that will be passed by a few people for their input too.
The worst thing for me is everything seems to look at maximum power rather than maximum duration of power (which is my aim).

I have plenty of time and no resources, so don't wait up!

Ha, no worries on that one.

I guess you have noticed lately that the more modern approach to porting is now towards a better spread of power, and sometimes finding resources on that can be difficult. (on the web any way)

I am guessing you have downloaded some of the PDF's made available...... the basics is always the best place to start (even though some times it can seem boring!)

[SS90]

Exhaust Duration of 183 = Ex Opens 88.5 ATDC and Transfer Duration of 128 = Trans Opens 116 ATDC.

"you could go a few degrees higher"

Ex Opens 86.5 and Trans Opens 116 ATDC.


.

Yea, as I have posted in the ESE thread, my experience over the last few years has shown that with modern set ups (scavenge patterns,primary compression ignition timing) you can get some very good power engines with some quite "low" port timings and durations.

so yea, Opens 86.5 exhaust would be 187 Duration.

The cylinder I designed the last 2 years, is 188 Duration ex, and 131 Transfer, and that (seemed) to be the best compromise for power/torque and spread of power.

Of course those figures are nothing new (I think Teeezee pointed out old air cooled Rm125's where something like that), but it is quite amazing what "the modern approach" will achieve with the same port timing set ups!

It seems from the measurements of the M1L cylinder I made today, that the exhaust duration is indeed 182.1 deg. (secondaries 179.8) and the transfers 127.9 deg (with a 5mm base gasket)

I personally think that it could go (like you say) to 187 or indeed 188, it is quite surprising to me, from the dyno runs I have seen (with quite poor results) I made the assumption (with-out ever measuring a cylinder) that there was simply too much exhaust duration.

After measuring today, I caclulate the following thickness gaskets will give the following port heights

No gasket transfers 125 exhaust 179.9 secondary exhausts 177.6
0.2mm gasket transfers 126.2 exhaust 180.8 secondary exhausts 178.5
0.35mm gasket transfers 127 exhaust 181.4 secondary exhausts 179.2
0.5mm gasket transfers 127.9 exhaust 182.1 secondary exhausts 179.8

Quite a bit lower that I thought it would be.

With the 5mm gasket, you also have 1.25mm squish clearance.

Personally, I think it would be logical to build the engine to the specs planned, and new exhaust) do some base runs (see what the curve looks like) and perhaps look at increasing the timing of the exhaust and transfers.

The attached dyno run is of a "plug and Play" version of this cylinder (exhaust unknown to me)

[SS90]

Ok, in the interests of putting a value to the primary compression ratios applicable to modern porting and exhaust designs, I have modified a crankshaft (just using logic as to how much material to remove, making a cardboard template, and marking with a yellow spray bomb ), and, as I assemble the engine I will measure the crankcase volume at TBC and at BDC, so as to calculate the primary compression ratio).

I will then compare the dyno curves to 4 other known "high tuned" engines ( 3 other tuner have agreed to send me some dyno runs for comparison) with the same cylinder (I don't know what primary compression ratios other are running, and also the exhaust being used is a prototype, so it will be an interesting comparison.

I will also use a retarding ignition, and using different CDI/coil units establish which "retard" curve is best (for this cylinder/pipe/primary compression ratio combination.

I will also measure the exhaust gas temperature.

I have also found the the standard "Transfer stock" ( fully open point at BDC) is about 1mm too high.

I am certain this was not intentional by the designer and is more likely a manufacturing/casting fault.

As such, I have sent the crankcases to have 1mm removed from the cylinder base. I'll pick them up on the way to work tomorrow, it is a little dissapointing, as it involves more work.

I currently still am of the opinion that the standard exhaust port duration is too low, and I really am considering raising it to 188 Deg before assembling it.......

[Brian d marge]

I would be very interested in how this goes , if i knew the weights and could calculate the forces I could put it through a FEA program

Stephen

[bucketracer]

Broad power is my aim - I don't give a rats about peak power.

Hi Skunk this may be of interest "How to Choose a Power Band" by Eric Gorr.

http://www.whidbeyparts.com/info/Howtochooseapowerband.pdf

.

[TZ350]

.

Something else that you might find usefull.

MSV Mean Squish Velocity Calculator:- http://myweb.tiscali.co.uk/teamsparrow/cylinderheadsv2_3.xls

.

[speedpro]

It'd be interesting to know what the balance factor is with the crank cut down like that. I would guess it's tuned for very low revs unless you are using iron pistons.

[Skunk]

Hi Skunk this may be of interest "How to Choose a Power Band" by Eric Gorr.

http://www.whidbeyparts.com/info/Howtochooseapowerband.pdf

.


.

Something else that you might find usefull.

MSV Mean Squish Velocity Calculator:- http://myweb.tiscali.co.uk/teamsparrow/cylinderheadsv2_3.xls

.Now that's what I'm talking about! Cheers guys.

Now I have to learn what it is I want with MSV...

[SS90]

It'd be interesting to know what the balance factor is with the crank cut down like that. I would guess it's tuned for very low revs unless you are using iron pistons.

No (Iron pistons in two strokes have fallen out of fashion at the last ice age):laugh:

I am fairly confident it will be ok...........

Time will tell.

I assure you I will post any findings (good or bad)

At this stage I really am keen on finding a minimum value!

[SS90]

OK,

Today I picked up the cases from the Machine shop (after having 1mm removed from the top)

I then matched the original Piaggio Vespa cases to the new Quattrini cylinder, before dry assembling the crank in the cases (to measure the primary compression ratio...no point in explaining how to go about that, it has already been covered in the ESE thread)

It turns out that with the "modified" "racing" crank (pictures above) the primary compression ratio is 1.42:1

This is certainly the lowest I have (deliberately) gone!

So, I emailed a friend of mine (who last year worked for KTM, and now works in Italy), and asked him his opinion of crankcase volumes (and in particular minimum values)

The following is an excerpt from his reply.

I would also add that (like he mentions) some of the things mentioned in the article linked, are not 100% correct, however, it is a fresh prospective on quite a few aspects of two stroke tuning.

That's always nice!

hi (SS90),

the primary compression is often misunderstood. for low rpm, a high primary compression is benefitial (because the crankcase then works as a pump). for high rpm, a low primary compression is benefitial (because the crankcase can then store enough gases for a good filling). but where do the "low rpm" end, and where do the "high rpm" start? and what type of performance do you want to obtain?

even charlie edmonds got it wrong in his very interesting "scootering" interview.
http://www.lambretta.it/eddy/edmonds.htm

he makes it sound like low primary compression is a key to finding power. this is correct when related to a scooter engine (they have very high primary compression ratios of 1.5...1.6), but he makes it sound like there's no minimum value. also, he refers to motocross engines, and makes it sound like they reduced the primary compression purposefully. truth is that on motocross engines the conrod length was increased to reduce stress on the piston, and ports were increased for more power. but the reduced primary compression was only a side effect. truth is that at ktm we put a lot of efforts into increasing primary compression, because midrange is very important on an offroad engine.

the lowest primary compression i have seen is the aprilia gp engine with something in the 1.25 range.

with the modified crank (looks nice) like you say, you have 1.42:1. quite good for a vespa engine and its requirements. of course you can still argue about whether you'd be willing to trade 1nm at 6000 rpm for 1nm at 9000 rpm...

(He finishes later with)

bytheway, the best 50 tuners in the world are dutch!

So, with 1:42:1, it sounds like it is a good "middle ground"

This particular engine will rev to 10,000 RPM (as do my own cylinders), which run a primary compression ratio of 1:47:1

depending on the results of this engine, I will look at decreasing future engines (that rev to 10,000 RPM)

It will be nice to have hard data as to "how low you should go"

and it would seem with the constraints placed on some buckets (available gear ratios), it would seem logical (so far) that between 1:4 and 1:45 (for high revving 6 speed transmission) and for "low revving 4 (or maybe 5 speed transmissions) 1:47 is somewhere "in the ball park"

Due to the different maximum exhaust port time areas (and maximum RPM) suitable for each type.

Let's see!

One good thing about having to change the cylinder height is that now I have to change the combustion chamber....any opinions welcomed on that one!

Looking at some of the things Teezee and Chambers has posted links to gives a few options.

Like Skunk, I like non squish heads personally.

[bucketracer]

From page 66 of the ESE thread.

The effects of crankcase volume on the delivery ratio:-
http://www.edj.net/2stroke/jennings/crankcase_volume.pdf

Section 1.5 of the Discussion section on page 14 is worth reading.

[TerraRoot]

Thanks for the info ss90! can't wait for the results, good or bad least we will know.

[Skunk]

Like Skunk, I like non squish heads personally.
Having read this:

http://www.whidbeyparts.com/info/Howtochooseapowerband.pdf
I'm in two minds now. I have a spare head so I may do a squish and a non-squish to see the difference. I'm aiming to set up the squish to make the MSV around the 30m/s figure. The current squish head seems to be around 25m/s.

[SS90]

Primary compression aside for a bit,

I was talking today to 2 people who own/ride these quattrini M1L cylinders (just "plug and play", no work.) (17PS) and they both said the same thing.

"it uses alot of petrol"

That seems odd to me, as they only have 17PS.

This (in my opinion) would indicate that something is upsetting the scavenge pattern.

So, I started looking hard at the scavenge patterns, and in particular, the boost port angle.


I measured the boost port at 55 DEG (that's what I expected)

Now, these cylinders have very large "blow down times" in the transfers, (which would indicate VERY high RPM "power bands")

So, after some careful measurements I have decided to change the boost port angle, to better match the transfer timing.

I now believe I can safely increase the exhaust port duration to where I want to.

I also took the crank to a machine shop today to calculate the balance factor... I believe that balance shafts are for FAGS, but it would be nice to know!

[bucketracer]

So, after some careful measurements I have decided to change the boost port angle, to better match the transfer timing.

I now believe I can safely increase the exhaust port duration to where I want to.



"I have decided to change the boost port angle, " change to what?

"increase the exhaust port duration" increase from where to what?

Its very interesting to be able to watch your progress. Thanks SS90.

.

[Chambers]

SS90, from a SAE paper you refered TZ350 too.

Last paragraph page 175: The drop in delivery ratio caused by increasing the crankcase volume can be fairly well compensated for by tuning the inlet and exhaust system.

http://www.edj.net/2stroke/jennings/crankcase_volume.pdf

Second paragraph of the discusion section page 188: Small crankcase volume is best for high speed and large volume for low speed. Explanation: with small volume and low speed the crankcase discharges to fast into the cylinder and for the rest of the transfer-port-open period there is reverse flow.

Forth paragraph of the discusion section page 188: If the engine speed is selected to best suit the crankcase clearance volume the clearance volume does not effect the delivery ratio. Tuning either the inlet or exhaust pipe or both increases the delivery ratio.
.

So from reading the SAE paper, you have to have the right crank case volume for the intended engine rev's and it needs to be a smaller clearance volume ie., a higher primary compression ratio thats closer to 1.5:1 the higher the rev's.

I think your friend has it back to front and is wrong in what he has told you.



So, I emailed a friend of mine (who last year worked for KTM, and now works in Italy), and asked him his opinion of crankcase volumes (and in particular minimum values)

The following is an excerpt from his reply. "the primary compression is often misunderstood. for low rpm, a high primary compression is benefitial (because the crankcase then works as a pump). for high rpm, a low primary compression is benefitial (because the crankcase can then store enough gases for a good filling)."

"A low primary compression (larger clearance volume) is beneficial because the crankcase can then store enough gases for a good filling", sounds similar to what Speedpro was saying on the ESE thread too.

.

[Yow Ling]

"I have decided to change the boost port angle, " change to what?

"increase the exhaust port duration" increase from where to what?

Its very interesting to be able to watch your progress. Thanks SS90.

.

i think you are dreaming there bucketracer

[speedpro]

I also took the crank to a machine shop today to calculate the balance factor... I believe that balance shafts are for FAGS, but it would be nice to know!
I hope you took a bit more than the crank, it's a bit hard to weigh things if they aren't there.
I agree about the balance shafts for what we're doing. Mine's in the bin and I dealt to the crank and it's good. It shakes at low rpm but is fine where I use it so it doesn't matter.

[SS90]

SS90, from a SAE paper you refered TZ350 too.

Last paragraph page 175: The drop in delivery ratio caused by increasing the crankcase volume can be fairly well compensated for by tuning the inlet and exhaust system.

http://www.edj.net/2stroke/jennings/crankcase_volume.pdf

Second paragraph of the discusion section page 188: Small crankcase volume is best for high speed and large volume for low speed. Explanation: with small volume and low speed the crankcase discharges to fast into the cylinder and for the rest of the transfer-port-open period there is reverse flow.

Forth paragraph of the discusion section page 188: If the engine speed is selected to best suit the crankcase clearance volume the clearance volume does not effect the delivery ratio. Tuning either the inlet or exhaust pipe or both increases the delivery ratio.
.

So from reading the SAE paper, you have to have the right crank case volume for the intended engine rev's and it needs to be a smaller clearance volume ie., a higher primary compression ratio thats closer to 1.5:1 the higher the rev's.

I think your friend has it back to front and is wrong in what he has told you.



"A low primary compression (larger clearance volume) is beneficial because the crankcase can then store enough gases for a good filling", sounds similar to what Speedpro was saying on the ESE thread too.

.

Hmmm,


I think someone who designs two stroke engines for a living is "on the money" (personally)

I'll take his advise any day.

You are of course free to make you own mind on that.

Experience tells me that (as was mentioned) with modern high revving engines (Aprilia 125GP bike was used as an example) run high crankcase volumes.

What was mentioned was what is high RPM and what is low RPM.

It's a little subjective really.

So far my reasearch is pointing for an engine designed to operate in a rev range of around 10,000 RPM a ratio of 1:42 (roughly) would seem best.

Of course using modern exhausts and ignitions.

The lower the revrange, the higher (closer to 1:5) the better.

We will see.

Like I have said before, you need to put a value on every change you make "just lower it let the pipe do the work" is not very good thinking (in my opinion)

Have you ever read anything (anywhere) giving an indication to what is the correct primary compression ratio for a particular set up?

If not, what is your experience with different ratios?

I try not to take too much information off the web (reading the SAE papers written in the 60's in my opinion gives you an understanding of where people where in the 60's) but it does give you information on where others have been.

Like I indicated, this series of posts is trying to open discussion on what is a minimum primary compression ratio for a given engine set up, in particular operating RPM range.

You may remember in the ESE thread, I wrote about "what sort of power" you will get from a higher primary compression at higher RPM's.....much like a high exhaust port time area, you have a "stronger hit" of power (peakier power), and loose your ovverrev.

And from my experience, too lower a ratio will have almost the same effect (stops revving abruptly)

This is why it is prudent to put finite values on these these factors.

[SS90]

I hope you took a bit more than the crank, it's a bit hard to weigh things if they aren't there.
I agree about the balance shafts for what we're doing. Mine's in the bin and I dealt to the crank and it's good. It shakes at low rpm but is fine where I use it so it doesn't matter.

Logically I took "more than the Crank" (I was paraphrasing)

Like you, I have been doing this for a while:msn-wink:

Sure, I don't expect it to be sewing machine, but limits in how I can increase the crankcase volume mean the crank is the logical step.

There is actually no option for a balance shaft in these engines, so it is really "what I get is what I get":mobile:

You seem familure with balance factors etc Speedpro, maybe you could contibute to this thread with some experienced information that we could all read?

[SS90]

"I have decided to change the boost port angle, " change to what?

"increase the exhaust port duration" increase from where to what?

Its very interesting to be able to watch your progress. Thanks SS90.

.

Just re-read a page or 2 back, Bucketracer....I posted what I would like to have the exhaust port duration at (as well as the original specs, with graduated changes achieved with different base gaskets)

As for the boost port angle, I posted above what other people have found regarding fuel consumption (in relation to the meagre power made)...what's your opinion on the boost port angle now you have the same information as me?

I'm interested in your feed back!

[bucketracer]

Hmmm,


I think someone who designs two stroke engines for a living is "on the money" (personally)

I'll take his advise any day.

You are of course free to make you own mind on that.

I try not to take too much information off the web (reading the SAE papers written in the 60's in my opinion gives you an understanding of where people where in the 60's) but it does give you information on where others have been.



Yes your right, you should do that, your pretty safe as there has never been an honest but misguided tuner or charlatan in the hot up business.

Although the SAE paper was a proper academic study, I expect the laws of physics have changed since then, after all the 60's were a while ago.

.

[bucketracer]

I'm interested in your feed back!

Specs recorded from some of the motors I have too-tooed with over the years.


.............................CLEARANCE........SWEP T........COMPRESSION
.............................VOLUME (cc)....VOLUME (cc).......RATIO

RM125A
.....CRANKCASE.................403.00.........124. 82...........1.31
.....CYLINDER.....................9.00...........1 24.82...........8.20

RS125
.....CRANKCASE.................380.00.........124. 82...........1.33
.....CYLINDER.....................8.50...........1 24.82...........8.67

TM125R
.....CRANKCASE.................400.00.........124. 82...........1.31
.....CYLINDER.....................8.20...........1 24.82...........9.21

TZ250
.....CRANKCASE.................313.00.........123. 67...........1.40
.....CYLINDER.....................9.00...........1 23.67...........7.61

R125 Kart Motor
.....CRANKCASE.................460.00.........124. 82...........1.27
.....CYLINDER.....................10.00.........12 4.82...........7.25

KT100J
.....CRANKCASE.................320.00.........98.1 7............1.31
.....CYLINDER......................9.40..........9 8.17............8.03

KT100S
.....CRANKCASE.................250.00.........97.6 9............1.39
.....CYLINDER.....................8.90...........9 7.69............7.37


SS90 it looks like you will have to cut some more off those flywheels.

.

[Yow Ling]

Wonder what I was thinking ?

[SS90]

Specs recorded from some of the motors I have too-tooed with over the years.


.............................CLEARANCE........SWEP T........COMPRESSION
.............................VOLUME (cc)....VOLUME (cc).......RATIO

RM125A
.....CRANKCASE.................403.00.........124. 82...........1.31
.....CYLINDER.....................9.00...........1 24.82...........8.20

RS125
.....CRANKCASE.................380.00.........124. 82...........1.33
.....CYLINDER.....................8.50...........1 24.82...........8.67

TM125R
.....CRANKCASE.................400.00.........124. 82...........1.31
.....CYLINDER.....................8.20...........1 24.82...........9.21

TZ250
.....CRANKCASE.................313.00.........123. 67...........1.40
.....CYLINDER.....................9.00...........1 23.67...........7.61

R125 Kart Motor
.....CRANKCASE.................460.00.........124. 82...........1.27
.....CYLINDER.....................10.00.........12 4.82...........7.25

KT100J
.....CRANKCASE.................320.00.........98.1 7............1.31
.....CYLINDER......................9.40..........9 8.17............8.03

KT100S
.....CRANKCASE.................250.00.........97.6 9............1.39
.....CYLINDER.....................8.90...........9 7.69............7.37


SS90 it looks like you will have to cut some more off those flywheels.

.

Ohh, it seems like you keep all the data from engines that you have "too tooed with"....do you have any pictures of said engines?

I was under the impression that you where suggesting that I was going in the wrong direction with lower primary compression for a higher revving engine....yet these engines you claim to have "too tooed " with all have primary compression ratios lower than 1.5:1.....

Can you explain your reasoning?

[bucketracer]

Ohh,
Can you explain your reasoning?

Could but won't where would the fun be in that, I am enjoying watching you work through it for yourself and making your own mistakes, but if you read the SAE paper its obvious.

.

[SS90]

Ermmm,

Hang on a minute..... why can't you explain why you "too tooed" with these engines (and I am guessing lowered the primary compressions).....you didn't clarify what "too tooed" meant, but I am going to assume "tuned"

So, you are saying that the SAE paper suggests that I should INCREASE the primary compression..........

Yet, you, yourself chose to lower all the engines you have listed to more closely to what I am currently advocating.............

So, what where the results from these "too tooed" engines......?

Did you end up stripping them all down and increasing the primary compression closer to 1.5:1?

:niceone:

[SS90]

Specs recorded from some of the motors I have too-tooed with over the years.


.............................CLEARANCE........SWEP T........COMPRESSION
.............................VOLUME (cc)....VOLUME (cc).......RATIO


TZ250
.....CRANKCASE.................313.00.........123. 67...........1.40
.....CYLINDER.....................9.00...........1 23.67...........7.61


.
also, while the final figure of 1.40:1 is correct for a vtwin TZ250, I can't work out how you arrived at these primary compression ratio figures (any of them, just using this as an example)

Primary compression is calculated by dividing the case volume at TDC by the case volume at BDC.......

From the figures you posted, I can't calculate that (for any engine you list)

Can you explain?

[bucketracer]

No. no changes these are the standard figures as is.

The way I read it, the SAE paper says there is an optimum clearance-volume, rev's, port-time-area relationship. Where there is an optimum clearance-volume, any more or less and the transfer delivery ratio goes down.

The key being port-time-area and how quickly the crankcase discharges through the transfer ports at the chosen rev's ie 10,000rpm. Below that the pipe makes up for the worse transfer delivery ratio.

I suspect in the 60's the transfer ports were smaller than they are now and required a higher primary compression ratio than being used by more modern engines.

But the paper did say as the target revs go up the primary compression ratio also needs to go up. Sounds logical.

.

[SS90]

No. no changes these are the standard figures as is.


But the paper did say as the target revs go up the primary compression ratio also needs to go up. Sounds logical.

.

Well, that's what i am trying to establish some figures for...... like the figures you posted.......a "modern" TZ250 is 1.40:1......an RS125 1.33:1

From memory (I have owned and raced both these models) A 1991 TZ250B revs till 11,000 (primary compression ratio 1.40:1) a 1995 RS125R revs to 13,000 (standard, A kits more), and have a primary compression ratio of 1.33:1

Hmmmm,

I see a pattern forming here!:niceone:

Re-read Gordon Jennings chapter on Crankcase volume (he mentions the same SAE paper there)

He also gives some insight and opinion on the reasons people increased primary compressions in the first place.

Have you seen any modern literature that gives minimum figures for primary compression ratios (for different engine set ups (operating RPM,capacity exhaust design etc?)

[bucketracer]

also, while the final figure of 1.40:1 is correct for a vtwin TZ250, I can't work out how you arrived at these primary compression ratio figures (any of them, just using this as an example)

Primary compression is calculated by dividing the case volume at TDC by the case volume at BDC.......

From the figures you posted, I can't calculate that (for any engine you list)

Can you explain?

Your correct, primary compression is calculated by dividing the case volume at TDC by the case volume at BDC.

For the TZ250 try (313 + 125) / 313 = 1.399 or simply 1.4:1

313cc + 125cc is case volume at TDC and 313cc is case volume at BDC if you read Jennings you will find it explained there.

.

[SS90]

Your correct, primary compression is calculated by dividing the case volume at TDC by the case volume at BDC.

For the TZ250 try (313 + 125) / 313 = 1.399 or simply 1.4:1

313cc + 125cc is case volume at TDC and 313cc is case volume at BDC if you read Jennings you will find it explained there.

.

Er, yes.

But, "your figures" (correctly) quote the piston displacement of a TZ250 (for one cylinder) at 123.67cc

so,

313cc case volume at BDC
123.67cc piston displacement

would be, (313+123.67)/313= 1.395

so, using "your figures" the primary compression ratio of a TZ250 is 1.395
not 1.40:1 (as you state)

Also, you have not explained why these engines you listed run lower primary compression ratios that 1.5:1, when you are advocating that "the higher the RPM, the closer to 1.5:1"

Based on the SAE paper.

The figures you listed (then later said they where "standard" (unmodified)) are ALL lower than 1.5:1 (in fact, much like I have said, the higher the RPM,the lower the primary compression ratio)....the lowest being a 100cc Kart sport engine (which rev to 15,000), which runs at 1.31:1 (standard), followed by a Honda RS125, which runs at 1.33:1, (and revs to 13,000)


Can you please clarify for us all?

Are you advocating that all these engines should have their primary compression ratios INCREASED?

And, can you quote your "scientific" reason for suddenly increasing the piston displacement of this example from 123.67cc to exactly 125cc?

[speedpro]

I've been sitting back watching numbers being quoted and the variations being suggested for various RPMs. I would have thought the differences could easily be put down to errors when measuring. The latest quibble is over .001cc or .005cc. That is either 1cubic mm or 5 cubic mm. Does anyone actually think that small amount would measurably affect performance or even be measureable?

[Buckets4Me]

:corn::doobey:

:hitcher::not:

[Yow Ling]

I've been sitting back watching numbers being quoted and the variations being suggested for various RPMs. I would have thought the differences could easily be put down to errors when measuring. The latest quibble is over .001cc or .005cc. That is either 1cubic mm or 5 cubic mm. Does anyone actually think that small amount would measurably affect performance or even be measureable?


well obviously SS90 does, if it was a real problem you could slightly over torque the base gasket to correct the fault, or use a little extra goo when assembling the cases so it oozed into the crankcase a bit

[bucketracer]

so, using "your figures" the primary compression ratio of a TZ250 is 1.395
not 1.40:1 (as you state)

Can you please clarify for us all?

And, can you quote your "scientific" reason for suddenly increasing the piston displacement of this example from 123.67cc to exactly 125cc?


Just for you SS90

I was working in the proper enginering manner of using 3 significan figures, which is appropreate for discussing these compression ratios. I thought you would appreciate it.

I thought you would be familiar with this methodolagy, most Technical people are. But I will explain.

Since virtually all numbers used in engineering are based on measurements, they have inherent uncertainty. The number of significant figures implies the magnitude of that uncertainty.

The figure of 123.67 implies an error or uncertainty of measurement of +- 0.005, or 5/1000 of a cc that sort of accuracy is not likely but 124 implies an accuracy of +- 0.5cc which is much more likely.

In its simplist form, results of calculations are reported to 3 significant figures.

So reporting my results to 3 significant figures 1.395 with rounding becomes 1.40 and 123.67 would become 124 as well as the more realistic implied accuracy of measurement using 3 significant figures it also does away with unnessary numerical clutter.

As for using 125 instead of 124, nothing scientific about it. I used 125 to help you quickly see where the value came from. :msn-wink:

Rework the calculation with 125 and you will see the primary compression ratio for the TZ still points to 1.40:1

1/1000 did not change the big picture, amatuer people often get lost in small detail and then become confused, keeping it to 3 significant figures helps maintain clarity.

You can read more about significan figures and errors of calculation and measurement here, from the Stanford Engineering Dept no less:-

http://www.stanford.edu/class/engr1n/Precision_E1.pdf

So SS90 you learn't something new today.

Is there anything else you would like help with?

.

[SS90]

I've been sitting back watching numbers being quoted and the variations being suggested for various RPMs. I would have thought the differences could easily be put down to errors when measuring. The latest quibble is over .001cc or .005cc. That is either 1cubic mm or 5 cubic mm. Does anyone actually think that small amount would measurably affect performance or even be measureable?

Well put speedpro,

Speedpro, I am still interested in your experience (rather than quoting web pages) on balance factors for high performance 125cc two strokes....... can you write a few lines for us all?

While we are on the subject, it would be now perhaps prudent to suggest that accuracy is quite important when measuring volumes.

The only reason I "quibbled" over Bucketracers figures, is because I seriously doubt his experience.

I have said this before, but does Bucketracer have anything to contribute to threads other than antagonism?

He, so far (in this thread) has advocated that "the higher the RPM, the closer to a primary compression ratio of 1.5:1 (as per the SAE paper from the 60's).....(which, by the way, I was the first person to mention in this series of threads)

Yet, Bucketracer himeself posted figures of Japanese performance two stroke engines, (most high revving) all of which had ratios closer to 1.4:1.........

Now, perhaps now it would be wise to remind you what I am trying to establish with this series of posts.

With modern two strokes, the trend has been (actually, from the Japanese, this has been from the mid eighties) to decrease primary compression (the higher revving, the higher the crankcase volume.

Contrary to the SAe paper from the 60's. (written by the Yamaha engineer Fujio Nagao)

Why is this?

Well, one telling piece of information lies in the SAE paper.

"any deficiency in air delivery due to a crankcase volume too great for a given speed is fairly well compensated for by a properly tuned intake and exhaust pipe"



Ahem....

so....

any deficiency in air delivery due to a crankcase volume too great for a given speed

This, (to me) suggests that the speed (RPM) that your engine is designed for has an effect on what primary compression ratio best suits that engine.

either that, or we could all follow bucketracer advice and increase the primary compression on all the TZ250' and RS125's racing in the world....(maybe we could polish the transfers while we are at it....because, it would really go then!)

Hell, screw it, Bucketracer, send an email to Yamaha, "tell them how it's done"......tell them to increase the primary compression on their two stroke GP bikes........You will be a national hero for sure!


Let's also remember that in the 60's, expansion chamber, ignition and cylinder head design was somewhat "poorer" than it is today.........

That said, Gordon Jennings (by far my favourite writer) seems quite prophetic in his writings...particularly in regards to exhaust design VS primary compression ratios (and the spread of power)......he actually mentions "much lower that a ratio 1.5:1" when looking for a long spread of power opposed to peak power" in his book "THE TWO STROKE TUNERS HANDBOOK"

(in the chapter "Crankcase pumping")

Also, see what he has to say in regards to exhaust design (when looking for this particular "long spread of power"), then take a look at an up to date expansion chamber (I posted some pics on the ESE thread of something I have played a part in the design of 18 months ago, and certainly it is not "cutting edge", but could be considered "modern thinking")

Then, factor in modern approaches to "scavenge patterns", and remember that a good scavenge pattern "improves cylinder filling at high RPM" (particularly when coupled with modern transfer port design. (transfer port dividers for one), along with ignitions that apply retarding (later) ignitions the higer the RPM.... (giving "overrev" in the high RPM's, but also, by passing heat from the combustion on to the exhaust (rather than the cylinder), thereby changing the exhaust frequency (and as we all know, taking advantage of these changes is one of the things a good 2 stroke tuner does.)

While it as old book, it seems to suggest that there are advantages to be made when you build an engine with a particular purpose in mind.

I'M OFF TO THE PUB!:apint:

[Pudding]

Neil from the pm's that have been passed around I think Bucketracer is of the opinion your a bit of a tosser who is trying too hard. And if you can't back up what you say with a reliable reference or two he may be right.

In your last post you have continued to try and belittle Bucketracer.

Not many of us have forgotten your rant when Speedpro suggested the crankcase was just a place to store the air/fuel mix. With the larger crankcase volumes being advocated it looks like he is more right than wrong.

If you want serious input you need to stop belittling people who don't agree with you.

You asked for Bucketracers input, which he gave. You couldn’t understand it, and asked for clarification, which he also gave and interesting it was too.

Then to demand an explanation about the accuracy of his calculations because he confined his workings to only the significant figures was foolish, and in demanding an explanation, exposed your lack of knowledge in a way that invited the response you got.

In doing your own calculations you wrote down all the decimal places from your calculator, and thanks to Bucketracer you now know this approch hasn't any significance and is not the accuracy you imagin.

If you follow the link he provided you can educate yourself and be more informed about achiving significant accuracy in measurement and calculation.

You got what you deserved, learn the lesion and be-grateful that he took the time to explain accuracy in engineering measurement and reporting, to you.

Good luck with your efforts in getting your scotter sorted honey. LoL Pud.

.

[speedpro]

One thing that has not been mentioned is that what was "high" revving for an engine 20 years ago is pretty tame nowadays, 16,000rpm 600s for a start. It makes comparing (20 year old) apples with (modern) apples a bit difficult.

Anyway . . . . crankshaft balancing. Why more people don't do it I'll never figure out. The first one I did was a Suzuki TS100. Originally it cracked the pipe, frame, number brackets, and anything else on the bike EVERY time I rode it. I talked to lots of people including engineers working for the railways designing locomotives. These guys have serious qualifications but anyway the problem is a fairly simple one - the engine has a piston going up and down. The forces are proportional to piston speed. It also has a crankshaft spinning. The crank forces are proportional to the square of the speed of rotation. The problem therefore is that the forces increase at different rates and can only more of less equal, and counteract, each other at one speed. The TS100 was designed so that they equalled at the speed the cockies used them at - slow. The crankshaft forces ramp up pretty quick so the start point had to be lowered - ie the amount of weight opposite the big end pin had to be reduced if it was going to all even out at the revs I was using. After speaking to some old guy who used to race singles I just pressed a couple of slugs of alloy into a handy hole in each web up next to the pin and gave it a run to see. It was all sweeeeeeeeet.

The Honda crank was a bit different as it had a balance shaft but the principle was the same though I made a lot of measurements and decided on the engineering changes based on my measurements.

[bucketracer]

While we are on the subject, it would be now perhaps prudent to suggest that accuracy is quite important when measuring volumes.

I have said this before, but does Bucketracer have anything to contribute?



Yes "accuracy is quite important" and now thanks to me SS90 you know how to achieve that, and produce a meaningful result by using only the significant figures in your calculations.

A positive contribution, a real gem, thanks Bucketracer.

That’s ok SS90, with practice you will get quite good at it and it will serve you well, as you will look so much more professional, inteligent and educated when you use it and less self tought and desperate to make a name for yourself.

In fact in that one tip about making accurate measurements, calculations and producing meaningfull results I have given you an insite into something far more valuable and usefull than anything you have given us in all of your posts to date.

.

[Buckets4Me]

:jerry::jerry: :niceone: :clap: :wari:

[saxet]

This is worse than watching kids argue.

[TerraRoot]

nah kid's are entertaining arguer's(ur a donkeys hed!). this is more like dick measuring teenagers.

[Buckets4Me]

just because mine is bigger than your's

:bleh:

[F5 Dave]

Well I've been away for a while using my considerable skills & experience where they are better employed (I've been wiping my own arse since I was a little boy so I suppose I am somewhat of an expert, though the hours these little guys keep is a bit of a struggle).

Anyway just to back the truck up a tickle. Skunk, first raise the barrel to the transfer height desired & adjust the exhaust up if required as it's easier to do that transfers. The inlet will need to go down, but be careful as if you make TS/TF barrels inlets too wide down low they will crack the barrel sleeve stub off.

That after market barrel SS posted looks quite good, but the transfer passages look pretty parallel to the bore rather than sweeping.

[bucketracer]

That after market barrel SS posted looks quite good, but the transfer passages look pretty parallel to the bore rather than sweeping.

TZ or was it Thomas? whatever, on the ESE thread page 66 I think, one of them posted a link to a SAE paper from Yamaha that showed the sweep of the transfer passage was the second most important factor.

And it had a significant effect on power and torqe, the larger the sweep the better more or less. Follow the link and the paper can be downloaded and printed out, its worth a look.

[bucketracer]

this is more like dick measuring teenagers.


So who is the biggest dick then?


(Extracts From Wikipedia) "A study published in the September 1996 Journal of Urology concluded that average erect length was 12.9 cm (5.08 in) (measured by staff) Erection was pharmacologically induced :doctor: in 80 physically normal American men (varying ethnicity, average age 54). It was concluded: “Neither patient age nor size of the flaccid penis accurately predicted erectile length"

"Erect circumference was an average of 12.6 cm (5.0 in)."

"A study published in BMC Women's Health, surveyed women's preferences concerning penis size and concluded that width rather than length is a more important factor of sexual stimulation."



Great stuff mines bigger than average :bleh:


Yes it sure is silly...... But ........ how do you measure up? :niceone:

[speedpro]

Ok, in the interests of putting a value to the primary compression ratios applicable to modern porting and exhaust designs, I have modified a crankshaft (just using logic as to how much material to remove, making a cardboard template, and marking with a yellow spray bomb ), and, as I assemble the engine I will measure the crankcase volume at TBC and at BDC, so as to calculate the primary compression ratio).

from post #63

So. . . . . How did that crank work? I'm expecting a report of lots of vibration above idle. So much in fact that you probably wouldn't run it up to check power differences. I'm keen to know though.

[SS90]

from post #63

So. . . . . How did that crank work? I'm expecting a report of lots of vibration above idle. So much in fact that you probably wouldn't run it up to check power differences. I'm keen to know though.

Quite acceptable vibration actually....

42% factor..... not much, but very little I can do to change that (with-out Tungsten)

Small Frame Vespa engines are of course Rubber mounted, so that does help.;)

Of course like I said, I am trying to find minimum values for primary compressions, and how you increase the volumes of your crankcase (to lower the ratio) is up to whoever is doing the job (removing material from the cases is one option, but in this scenario is not really feasable, and since I wanted to lower the blowdown time of the transfers (by removing 1mm from the case faces) I had actually INCREASED the ratio, so removing material from the crank was my only real option)

If, as is (SOMETIMES) the case (depending on the cylinder and it's intended purpose) you need to space the cylinder up....therefore increasing the crankcase volume (and lowering the ratio) by default.....in this instance spacing the cylinder up was the exact opposite of what I needed to do.

Like I say the vibration level is totally acceptable (I am sure the rubber mounts are doing their job well!)

If it was a solid mounted engine, possibly it would be a problem.

The following attachment is the "first finished run".... (I previously posted a picture of a "plug and play" run ....16.8 PS).......Shortly (when the customer is ready) I would like to run a few degrees higher on the exhaust, and change to another exhaust (just for comparisons), as I expected a bit longer flatter peak power...this is quite acceptable, but that could well be due to the exhaust.

28mm dellorto PHBH28 (possibly the most basic carb on the market)
Prototype exhaust
Retarding Ignition
Port timing and primary compression ratio specs as per my previous posts

One big problem we have all found over here with exhaust designs is a resonance issue in the midrange, which took a bit of solving last year (the exhaust I used on this engine was designed to eliminate this (quite well actually), but it appears that it does come at the expense of the "length" (and amount) of peak power.

I am pretty sure with some changes to certain aspects of the engine I could run ALMOST the same dimensions as last years pipe, which has proved time and time again to have the most PEAK power (and longest spread), but unfortunatly required changes to engine set up that wasn't expected.

That will have to wait, as I have 2 more to build now.

But I am confident with the other exhaust system I would see 25 PS no problem.

It does also appear that I was correct in my thoughts that the high blow down times on the transfers was a major contributing factor in the poor performance of these cylinders, (by poor performance, I mean a narrow power band, and no bottom end to speak of, coupled with a surprisingly low peak power figure for an air cooled 125cc aluminium cylinder)

Which is most likely because this particular model of cylinder was "adapted" from a Kart sport cylinder, (which typically have blow down times approaching revs more like 15,000 RPM, as well as a narrow RPM range. Which clearly does not match the exhaust port height the cylinder was produced with,( the original transfer times would suggest an exhaust port time area over 200 DEG), which would then require "power valves" to be useable.

Basically, the transfer ports where too high, hence removing 1mm from the crankcase, then raising the exhaust port height to suit. I would still go a few degrees higher on the exhaust port, it clearly can handle it, as even though they are lowered, the blowdown times are still more suited to a slightly higher exhaust port.


If I was to attempt to make a lot more power (more like 28PS,), I would approach the whole job differently, but such an engine, while very exciting to ride, has proven to be less fun that a torquey engine. (particularly when you are limited in your available gear ratios)

But, like I have stated previously it would seem there is a direct correlation between:-

exhaust design, carb size, intended RPM range, available gear ratios , ignition design and type and primary compression ratios.

Simply "one set up for all" is not correct.

Change one (particularly exhaust design) and if all the others are unsuitable for such a design, then you will most likely go backwards, rather than forwards, and perhaps notice no change at all, when if the engine was set up correctly you would otherwise see tangible gains.

But I still maintain it is vital to put accurate values on all changes you make, as clearly there is finite values for everything you do, not a "more or less" attitude (unless you find it important to keep some values to yourself, in the interest of competition!)

[SS90]

This arrived in my email just now...... A very clever guy, a series of runs he did last week, same type of cylinder, (heavily heavily modified), now experimenting with a new exhaust..... he didn't say what size carb, retarding ignition..... Same crankshaft cutting as the picture I posted......

Quite a lot of work, (made 2 exhausts just for the testing) but the results speak for themselves....

[k14]

Woah that is crazy, you are getting within the realms of a RS125 engine there!

One thing I've been meaning to ask is what do you guys use these engines for? Is it just for rich scooter boys or do they race them over there?

[SS90]

While most of our customers are from Germany (at I guess the majority of these guys could be considered "wealthy", as to build an engine of this type complete with exhaust, carb, ignition, machining and labour is quite high, although some customers will save all year for an engine that will put out "more than 23 PS and 20 NM")


I do have a few jobs occasionally from France and recently England.

Predomanantly these are for the road!
(quite frightening really, but all pass the tough TÜV regulations, so are legal), but I now get more and more enquiries from guys who race them, and it is clear that for the A grade class, 30 P.S AND 24 NM is the standard.

2 years ago 20 PS was the standard, just goes to show how things improve with competition!

[speedpro]

Quite acceptable vibration actually....

42% factor..... not much, but very little I can do to change that (with-out Tungsten)

Small Frame Vespa engines are of course Rubber mounted, so that does help.;)



Just looking at it I expected more like 70-80%. At 42% it would actually get better at the upper end, and further, of the engines rev range. You need to track down a bit of Mallory metal.

[bucketracer]

Woah that is crazy, you are getting within the realms of a RS125 engine there!

These big Hp Scooter motors are more than 125cc.

We need the cc's and Hp to make a comparison but from what I've seen, in realitive terms, Speedpros Bucket seems to be in the same ball park.

.

[FastFred]

Quite acceptable vibration actually.... 42% factor..... not much, but very little I can do to change that (with-out Tungsten)

42% REALY!!!!!


Closed loop fuel injection is shit you say?

Can you please explain WHY closed loop fuel injection is shit Ducatirider....???????

(I'm really interested in hearing an 18 YEAR OLD BOY explain why closed loop fuel injection is shit..........)

http://www.kiwibiker.co.nz/forums/newreply.php?do=newreply&p=1129245243

.

SS90 as cranks are traditionally balanced to 60-65% and your so fond of dumping on people maybe a "BOY" like yourself can explain how removing material from the big end area of the crank reduces the balance factor to 42%.

Me thinks you’ve got it wrong, and don't realy understand how balance factors are determined, which is surprising for a self confessed Ace Engine Tuner.

[SS90]

These big Hp Scooter motors are more than 125cc.

We need the cc's and Hp to make a comparison but from what I've seen, in realitive terms, Speedpros Bucket seems to be in the same ball park.

.

No, these graphs are from 125cc engines.

There are indeed 140cc (aircooled) engines (quite a few), the following graph is from one.........

However, they don't last very long at all (see second picture), as with the longer stroke cranks used piston speeds start getting too high.

Setups like this really are only for quartermiles, and parts like crankshafts, pistons bearings don't last very long at all.

It's just a matter of which one breaks first.

But like I say, 30PS 125cc aircooled engines are an everyday occurance in Europe now

A small few have 140 (some 150cc) 35PS 25NM engines

I think the reason so many clever guys over here get into it, is because with the tough (E4) emmission laws, there are pretty much no road legal "performance" two strokes allowed on the roads in central europe anymore (that will change in the next 5 years, I am certain)

The exception being any "classic" vehicle (which is totally exempt from emmissions and noise testing), so that provides a platform for tuning that would otherwise be impossible.

Yes, certainly 35 PS on a small frame Vespa is completely dangerous, they handle like turds, but it's the only vehicle you can ride that's been modified.

The best power is obtained from the "scootermatic" boys (huge industry), but as they are subject to emmissions testing, they can't be ridden on the roads and are limited to use at quartermiles.

[SS90]

42% REALY!!!!!



SS90 as cranks are traditionally balanced to 60-65%

Really? 60-65% ?

Maybe it's because I am on the other side of the world, but I was under the impression that 50% was the norm for such applications.

Is that not correct?.

The crank I modified was an "old school" designed "full circle crank", that are an after market part, designed only to increase the primary compression. nothing else.

In fact, full "circle cranks" completly destroy the balance factor, and the engines vibrate terribly.

The second picture attached is of an original crank (designed for disc valve), the other is a "full circle" (designed to be used with a "piston induction (reed valve conversion) cylinder.

Notice the amount of material around the pin? the other side of the crank is only like that, because it is used as the "disc valve" portion of the engine (quite different to a Japanese engine) if that was not required, the crank webs would be symmetrical.

Basically, the "full circle" cranks have a terrible balance factor, and in so far as tuning goes, they have proven their best use is only as a "blank" to enable you to make your own.

These where originally designed from the "old school "raise the primary compression", however, they raise it it 1.6:1

Original cranks are closer to 1.48:1

I'm quite happy with the fiqures I posted.

Remember that the "full circle cranks" are not original.

[bucketracer]

No, these graphs are from 125cc engines.

There are indeed 140cc (aircooled) engines (quite a few), the following graph is from one.........


I got the idea these big Hp Scooters were bigger than 125 cc from the link you posted http://www.lambretta.it/eddy/edmonds.htm posted page 5 of the “Two-stroke performance tuning?” thread.

Where Charlie Edmonds talks about his 225cc 37Hp 07 BSSO Championship winning scooter and the “Vespa 180 VE Small Frame” tag on the dyno charts you posted. And amongst all the Scooter hot-up cylinders I’ve seen while following your Posts, they all seem to be “Big-Bore” and about 200cc or more and in the so called 30+ Hp range.

The 125 scooters you build, are they using the traditional 56mm bore or the more modern 54mm bore?

The Charlie Edmonds article was a very interesting read. I see he has trouble with heat in the air-cooled engines and this limits the power output. To help with cooling he uses air ducts and a Yamaha MX head with a head insert, I bet he wishes he had thought of using a copper head gasket/fin like Thomas, ESE’s Engine Tuner has.

[FastFred]

Maybe it's because I am on the other side of the world,

Or possibly from another Planet!!!


Basically, the "full circle" cranks have a terrible balance factor, and in so far as tuning goes, they have proven their best use is only as a "blank" to enable you to make your own.

Hmmmm that full circle crank looks pretty much like most mid capacity Japanese 2-Stroke Cranks, but, what the heck, what would they know.

[TZ350]

There is a lot of talk about "Balance Factors", folks how about putting some numbers to the talk and a small explanation about how they are calculated from someone who knows what they are talking about.

If SS90, FastFred or someone else can't do it I will ask Thomas to write something for us, he's bound to come up with something interesting.

.

[SS90]

I got the idea these big Hp Scooters were bigger than 125 cc from the link you posted http://www.lambretta.it/eddy/edmonds.htm posted page 5 of the “Two-stroke performance tuning?” thread.

Where Charlie Edmonds talks about his 225cc 37Hp 07 BSSO Championship winning scooter and the “Vespa 180 VE Small Frame” tag on the dyno charts you posted. And amongst all the Scooter hot-up cylinders I’ve seen while following your Posts, they all seem to be “Big-Bore” and about 200cc or more and in the so called 30+ Hp range.

The 125 scooters you build, are they using the traditional 56mm bore or the more modern 54mm bore?

The Charlie Edmonds article was a very interesting read. I see he has trouble with heat in the air-cooled engines and this limits the power output. To help with cooling he uses air ducts and a Yamaha MX head with a head insert, I bet he wishes he had thought of using a copper head gasket/fin like Thomas, ESE’s Engine Tuner has.

The "VE number" is the number of runs you have done (starts at VE 001, and goes up from there)

(see attachment)

I assure you 125cc 30 PS is the standard over here.

140cc and 150cc 35PS

210cc-230cc ("big frame" engines) 40PS seems the level, but on the Vespa this is where the gear box breaks. (the shift fork)

The Lambretta's (when the gearboxes are modified (welded etc) seem to be able to handle it, others can also get them to 40 P.S

I have no experience with Lambretta (and very little on the "big Frame " Vespa.

Also, above 30PS, the small frame clutches have reached their limits, and it takes quite some work to get them to function correctly. But it is possible.

A standard 4 plate small frame clutch will take 15 PS, a basic modification will take 24 PS (and 20NM) and a little more work will hold 30 PS (or thereabouts)

Much over that is quite involved, but it is possible.

I must admit I was sceptical about what these engines could do when I started.

(tuned scooters? hahaha, you must be joking!)

It didn't take long for me to eat my words!

[SS90]

Or possibly from another Planet!!!



Hmmmm that full circle crank looks pretty much like most mid capacity Japanese 2-Stroke Cranks, but, what the heck, what would they know.

and such engines generally have balance shafts as well.

[SS90]

There is a lot of talk about "Balance Factors", folks how about putting some numbers to the talk and a small explanation about how they are calculated from someone who knows what they are talking about.

If SS90, FastFred or someone else can't do it I will ask Thomas to write something for us, he's bound to come up with something interesting.

.

Sure I can, I don't have huge experience, but I know SOME of the basics.

but I was hoping that other people can contribute to this thread (in an adult fashion)

I look forward to Thomas contributing.

What's his log in name?

[FastFred]

and such engines generally have balance shafts as well.

"Generaly" suggests more do than don't. Lets name them, Bet you can't name more that do than I can name that don't. I'll give you a head start Honda MB100 does. Yamaha RX and Suzuki A100 don't.

2:1 to me so far, now lts your turn, don't be shy, have a go.

[Chambers]

but I was hoping that other people can contribute to this thread (in an adult fashion)


For it to be adult you need to be adult yourself, your snide comments leave you open to a poke in return. You will have to sharpen up if you want to stimulate real adult discourse.

[TZ350]

Sure I can, I don't have huge experience, but I know SOME of the basics.


Some of the basics would be a good start.

.

[SS90]

Some of the basics would be a good start.

.

OK, the following is the data supplied to me from the machine shop.

( I would prefer to keep the modified specs to myself, but it's not hard to calculate)

Perhaps Thomas could explain it for us?

That's not a "snyde" comment incidentally.

It's quite an interesting subject.

Balance factor with original ("uncut" "full circle crank") used with the piston, gudgeon clips small end bearing supplied.

(60g+34g)/(60g+315g+10g)=25% (using Bucketracers suggested 3 decimal places method), other wise it would be 24.5%

The crank was measured as a complete assembly, and not dissasembled to be checked (quite an involved process)

[Chambers]

The whole of the rotating mass is balanced and only a portion of the reciprocating mass is balanced.

From memory: Balance factor for V8's and other V configurations 50%, multi verticals, twins fours etc 75-85% and singles 60-65%.

This is an interesting subject, looking forward to hearing more.

[TZ350]

The crank was measured as a complete assembly, and not dissasembled to be checked (quite an involved process)

Thomas tells me (after a quick phone call) its not that hard, a 100% of the rotating mass is balanced, this is always assumed and does not figure in the calculations. Only the % of the reciprocating mass to be balanced is calculated and this is where the balance factor comes from and is usually greater than 50%.

That is more than 50% and less than 100% of the reciprocating mass is offset (balanced) by the holes drilled in the flywheel near the bigend pin.

So the more holes drilled or metal removed near the bigend pin balances more of the reciprocating mass. So SS90, by cutting away the flywheel like he did increased the balance factor from something like 60% to maybe 80%. Ie more of the reciprocating mass was balanced by the remaining mass on the other side of the flywheels.

Thomas says its easy to find the reciprocating mass and balancing is very easy to do on a single statically but on multies you get better results balancing the cranks dynamically.

Its easy to chose a balance factor and balance an assembled single crank using knife edges but you have to strip the crank and re-assemble it with bob weights if you want to balance it dynamically.

The balance factor is a trade off between the vibrations going up and down or backwards and forwards in a single, or side to side in a multi, its your choice, chose your balance factor carefully.

He says there is no "correct" balance factor, only general ideas about what works and the real trick is to chose a balance factor from experiance that works with your frame and other reactive components like handle bars and foot pegs, also vibration robs power as the energy that is going into shaking things about is energy that is not turning the back wheel.

Finding the reciprocating mass and balancing a single crank is easy chosing the right balance factor is the trick.




So there it is, from the man himself, as best as I remember it.



.

[quallman1234]

Will a balanced crank make the engine be able to rev more freely, or simply just reduce vibrations?
A bit of a hypothetical/dumb question. But nevertheless.

p.s I now have a tf125 (6 speed).

[SS90]

Thomas tells me (after a quick phone call) its not that hard, a 100% of the rotating mass is balanced, this is always assumed and does not figure in the calculations. Only the % of the reciprocating mass to be balanced is calculated and this is where the balance factor comes from and is usually greater than 50%.

That is more than 50% and less than 100% of the reciprocating mass is offset (balanced) by the holes drilled in the flywheel near the bigend pin.

So the more holes drilled or metal removed near the bigend pin balances more of the reciprocating mass. So SS90, by cutting away the flywheel like he did increased the balance factor from something like 60% to maybe 80%. Ie more of the reciprocating mass was balanced by the remaining mass on the other side of the flywheels.

Thomas says its easy to find the reciprocating mass and balancing is very easy to do on a single statically but on multies you get better results balancing the cranks dynamically.

Its easy to chose a balance factor and balance an assembled single crank using knife edges but you have to strip the crank and re-assemble it with bob weights if you want to balance it dynamically.

The balance factor is a trade off between the vibrations going up and down or backwards and forwards in a single, or side to side in a multi, its your choice, chose your balance factor carefully.

He says there is no "correct" balance factor, only general ideas about what works and the real trick is to chose a balance factor from experiance that works with your frame and other reactive components like handle bars and foot pegs, also vibration robs power as the energy that is going into shaking things about is energy that is not turning the back wheel.

Finding the reciprocating mass and balancing a single crank is easy chosing the right balance factor is the trick.




So there it is, from the man himself, as best as I remember it.



.

I see,

So (from the figures I posted of the "full crank", which showed 25% balance factor)

According to Thomas the crank I started with had a factor of 60%....however it has been measured at 25%. (measured at 12 o'clock position)

So Thomas is correct when he told you I increased the balance factor.......

........ from 25% to 42%

(not from 60% to 80%) as Thomas suggested

I was hoping Thomas could explain the effect of cylinder angle on chosen balance factors as well.

Of course I am not advocating balance factors so askew from the "norms" it however what I achieved when I cut the crank to get the primary compression ratio I wanted. (I thought I had made that clear)

The rubber mounting of the engine cope well. (It has been done before)

Is Thomas suggesting I should have cut the material from the side opposite the pin? (.......that's what I think Thomas is suggesting)

What does Thomas think of the primary compression ratios I am using/advocating (dependent on exhaust design)

What does Thomas think a good balance factor is for such an engine? (like I said, a full circle crank is 25%, so 42% is better....( but like I said, not quite right, and like I said, Tunsten (actually Speedpro quite rightly suggested "Mallory Metal" (an alloy of Tungsten that is free machining, but I'll wager quite expensive!)

For balancing purposes I would like to take more material off the crankpin area (but I fear that would weaken the crank too much.)

[SS90]

Will a balanced crank make the engine be able to rev more freely, or simply just reduce vibrations?
A bit of a hypothetical/dumb question. But nevertheless.

p.s I now have a tf125 (6 speed).

Without having any thing to back it up, my experience is yes, a perfectly balanced engine does spin up better.

Have you ridden a pre 1995 Honda Rs125R?

My god, (no balance shaft (full circle crank), they where physically exhausting just riding 10 laps.

By comparison the 1995 and later (balance shaft) where like a Toyota Corolla (comparitively that is) Yet, the crank weighed the same (well near enough I guess)

[SS90]

I had to ask someone but apparently an original crank (like the picture I posted above) is "around 50%" originally

Adding more material arouond the pin (like a "full circle") decreases this "balance factor"

Like I showed....to 25%.

[TZ350]

I see,

So (from the figures I posted of the "full crank", which showed 25% balance factor)

According to Thomas the crank......................................

So Thomas is correct when he told you...................................

-------------------not as Thomas suggested

I was hoping Thomas could explain................................

Is Thomas suggesting.....................................

.............................that's what I think Thomas is suggesting)

What does Thomas think of the primary compression ratios..............

What does Thomas think a good balance factor is...........................

I asked Thomas but he said he explaind what a good balance factor is and he can't do all the work for you.

He can't remember if there is anything in Jennings or Bell on crank balancing but there certainly is in "Tuning for Speed" and also there is plenty on the net.

You could do some reaserch of your own, on how to balance cranks. Thomas would be interested to see what you come up with.

I guess we all would.

.

[bucketracer]

(60g+34g)/(60g+315g+10g)=25% (using Bucketracers suggested 3 decimal places method), other wise it would be 24.5%


So SS90 has drawn me into this again. SS90 I explained to you that professionals work with significant figures.

Thats Significant figures not Decimal Places.

I don't know SS90 if your being deliberately obtuse or if your merely stupid.

Mmmmmm you didn't pick up the gift I gave you on significance and accuracy in measurement and calculation, and again you'v involved me unnecessarily so I guess that makes you stupid.

.

[F5 Dave]

Glad to see we are back sparring as normal, thought everyone had gone soft.

erm my pre 95 RS didn't vibrate that bad at all actually, yes the 97 I rode was probably smoother but not something I thought about (as opposed to man this thing is so much more roomy). They can vibrate a bit when jetting is off or perhaps the front mounts were broken or the crank turned on the web. That will make anything vibrate like a jackhammer.

[quallman1234]

Without having any thing to back it up, my experience is yes, a perfectly balanced engine does spin up better.

Have you ridden a pre 1995 Honda Rs125R?

My god, (no balance shaft (full circle crank), they where physically exhausting just riding 10 laps.

By comparison the 1995 and later (balance shaft) where like a Toyota Corolla (comparitively that is) Yet, the crank weighed the same (well near enough I guess)

No haven't ridden a pre 95 one.
The one i use is a 98 i believe, and is very very smooth with very little vibration.

The TF125 is quite viby (no balance shaft), hopefully adding another engine mount will stablise this enough too ride.

[F5 Dave]

If you run the TF at reasonable revs it will vibe like a beast, I'd read Spodpro's post carefully with what he did to his, I won't offer any real advice as I've never had to tackle this issue so never researched it with more than a cursory glance.

[Pudding]

A quick search on the net for "Motorcycle Crank Balance Factor" and I found a lot of talk about factors ranging from 55% to 85% and in general the factors were 60-65%. There was one place that talked about 50% with a balance shaft but I saw no low numbers like 25% that SS90 talks about.

[Skunk]

Glad to see we are back sparring as normal, thought everyone had gone soft.
Yeah, without the sniping it would just be informative rather than entertaining as well.
I'm planning a 400 twin at 90° firing so this balance stuff is of interest to me.
Thanks for the info so far.

[saxet]

Think I'll go and watch something with a better I.Q. level involved..maybe Jerry Springer. I'd rather listen to banjo's than this.

[FastFred]

Yes, its a bit more intelligent over on the ESE Works Engine Tuner thread.

[speedpro]

I made a jig that allowed the crank to rotate freely on bearings. Then I laid the rod out horizontal with the piston, pin, rings, and clips and weighed everything on the end of the rod, including the end of the rod. Being horizontal the measured weight of the rod end effectively was the reciprocating part.
Next I made a small double ended arm with a free pointer rod at each end. The two rods balanced each other. Each rod was attached to the arm at exactly .5 the stroke and therefore were centred on the bigend pin. I attached the arm to the crank with one rod mount centred on the bigend and hanging down. The crank main pin and big end pin were horizontal. Because the crank was free to rotate the other little rod was free to press down on a pair of scales. I measured the weight being applied to the scales by the rod. When this measurement was made the rod was still horizontal and therefore the rotating end of the rod contributed to the measured weight, actually it reduced the measured weight. The % was simply the weight measured at the little rod divided by the piston weight etc.

[Skunk]

I've read that several times and still can't picture it. Got a diagram?

[k14]

I've read that several times and still can't picture it. Got a diagram?
Glad you're not the only one!!! :scooter:

[speedpro]

I'll get the crayons out

[Skunk]

Ya taking long enough... is ya zimmer frame broke?

[Kickaha]

Ya taking long enough... is ya zimmer frame broke?

Thats abuse, you causing trouble again?:Pokey:

[speedpro]

Had other things to do.

[Buckets4Me]

I now see why your engine fell apart in such a short time

nothing is straight or round it's all over the place

on a more sober note you planning to get to Taupo this year ?????

and or Mt Welly this weekend ??

[Skunk]

Ahh, I see now. Clever. Only I've got two rods at 90°. Hmmm, might pay someone. I just need to get an idea of the balance factor I want.

[SS90]

The % was simply the weight measured at the little rod divided by the piston weight etc.

Nice work Speedpro. I was wondering if you had the data from that work? just so we could see what factor you got.

Teezee, I was just wondering how Thomas was getting on with his explanation/pictures. (Tell Thomas no pressure!)

Just remind Thomas that the correct balance factor is chosen on a variety of factors (capacity, intended purpose (rpm's etc), method of mounting ("isolator blocks" or not) just as an example, but also angle of the cylinder in relation to the crank ("laydown", or "straight up")...both have different ideal balance factors (which then change again, dependent on the above factors.


Also, remind Thomas the type of balancing procedure (method) used is also dependent on rod position. (%age at what position?)

Also, remind Thomas of why I cut this crank in the first place, (and the shape chosen was not "random", and the amount of material I used was dependent on the crankcase volume I wanted.)

As I have previously stated I would remove MORE material from around the crank pin area to better balance the crank (or like Speedpro suggested use Mallory metal on the opposing side)

I am looking forward to Thomas's posts on this subject.

Tell Thomas I said Hi!

[TZ350]

SS90 Thomas has already covered here and in the ESE thread most of the things you are telling me to remind him about, it would be a bit like telling someone how to suck eggs.

He says others have posted some prety good ideas and that anyone can open a free account with Scribed where they can download "Tuning for Speed" by Phill Irving.

You could get yourself a copy, its an interesting read.

http://www.scribd.com/doc/15392252/Tuning-for-Speed-P-E-Irving-1965-Tuning-Racing-Motorcycle-Engines

Phill Irving talks about CrankShaft Balancing and Balance Factors on pages 107 to 110 of the book which can be found on page 61 of the PDF.

Thomas says it's all anyone needs for working on a single cylinder crank.

.

[SS90]

SS90 Thomas has already covered here and in the ESE thread most of the things you are telling me to remind him about, it would be a bit like telling someone how to suck eggs.

He says others have posted some prety good ideas and that anyone can open a free account with Scribed where they can download "Tuning for Speed" by Phill Irving.




.


Perhaps you could remind Thomas that, much like his early ESE racer engines (designed by taking too much information from an outdated, (yet in depth) book has the effect of building an out dated engine.)

Like the expansion chamber and port time areas Thomas built for the bikes (based on 70's tech), he got a 70's tech engine.

Now, I first read the Phil "slide rule" Irvine book when I was 18.

If I remember correctly, it was first printed around 1965.

Logically, certainly, not EVERYTHING printed in a 1965 is out of date, but if you where to take everything in there as gospel, you will end up with a 4 stroke engine reminisent of a Vincent Black Shadow (the bike he is credited for developing)

Certainly tecnologically advanced for the day, but by todays standards "a little bit behind the times"

Like with the ESE bikes, Thomas got engines reminisent of 1976 RM125's (because he simply "did what the book said".......Maybe if Thomas rode a 1976 RM125, then rode a 2001 RM125.... he will see what I mean.

While Thomas is having his eggs for dinner ( chewing is ok....he doesn't need to suck them) he could remember that, like I have previously written (pressure points being very important when dealing with Two stroke power), such things must be taken into account when choosing the correct balance factor.

Remind Thomas again (just to take away confusion) that I do not advocate 42%...... I advocate more like 50% (in this type of engine)

Has Thomas told you when he is going to have the time to write a few things himself? (he said he would)

I look forward to Thomas's experience with such things. Because the link Thomas posted is Phil Irvines experiences (in the 60's) I am interested in Thomas's experiences....as Thomas always says "it's the Buckateer way"

[TZ350]

.

SS90 you do seem overly obsessed with Thomas, as Thomas says, you can make a mountain out of a mole hill if you want too or you can KISS.

.

[SS90]

.

SS90 you do seem overly obsessed with Thomas, as Thomas says, you can make a mountain out of a mole hill if you want too or you can KISS.

.

Tell Thomas I am not obsessed with him, I would just like to see Thomas write something himself.... (Thomas did say that he would do that, including some hand drawn pictures)

Thomas (and his friends) where critital of my posts, and I would like Thomas to contribute (I would like to see Thomas show me where I am going wrong with my engines), because I really am interested in Thomas's input.

Can Thomas also explain the effect of primary compression on a balance factor?

[Chambers]

I am going wrong with my engines), because I really am interested in Thomas's input.


Your looking a little obsessed, its a bit obvious that your not genuinely interested in Thomas's input.

[Pudding]

SS90 your starting to look a little nasty.

[bucketracer]

SS90 your starting to look a little nasty.

Who's the little boy getting in a Tis Tis then ?

[SS90]

:killingme:killingme

[bucketracer]

I want, I want, I want, No I demand,
I demand, Nooooooo its not fair,
Wareeeeeee Mummy Mummy they are not playing nice.

They wont do as I say.

Tell them off Mummy
Tell them off or I will hold my breath untill I turn blue.


Seriously SS90, forget Thomas, get past him and contrabute something interesting yourself.

.

[SS90]

I want, I want, I want, No I demand, I demand, Nooooooo its not fair, Wareeeeeee Mummy Mummy they are not playing nice. They wont do as I say. Tell them off Mummy Tell them off or I will hold my breath untill I turn blue.



:killingme:killingme:killingme

[FastFred]

SS90 "I demand" does sort of sum it up.

You just don't have the persional touch that gets cooperation from people do you!

I can see, socially its always been a hard road for you hasn't it.

[SS90]

SS90 "I demand" does sort of sum it up, you just don't have the persional touch that gets cooperation from people do you!

Thomas? is that you?

[FastFred]

Thomas? is that you?


No SS90, it's GOD.... http://www.youtube.com/watch?v=cq-974EqCQI

.

[SS90]

No SS90, it's GOD....

.

:rofl::laugh::killingme:bs::drinknsin:doobey:

[TZ350]

.

SS90 How did you bring this on yourself?

Here is something to brighten you up. http://www.youtube.com/watch?v=7__-s6VsmAM

I am off to somewhere saner for the rest of the evening. :apint:

.

[Kickaha]

Now, I first read the Phil "slide rule" Irvine book when I was 18.

If I remember correctly, it was first printed around 1965.


It was first published in 1948 and then other editions in 1949,1951,1952,1956 and 1960

Doesn't everyone have a copy? :rolleyes:

[SS90]

It was first published in 1948 and then other editions in 1949,1951,1952,1956 and 1960

Doesn't everyone have a copy? :rolleyes:

Cripes!

Your right! things have moved on a bit since then.......... the basics are still the same, certainly, but really our understandings of different effects has improved somewhat.

Like I say, old book, old engine.

I must say, I am looking forward to Thomas's promised drawings/explanations!

[FastFred]

Like I say, old book, old engine.


The crankshaft goes round and round, the piston up and down.

I guess things have moved on and modern engines do it differently.

Can SS90 explain how, we are all waiting.

.

[SS90]

The crankshaft goes round and round, the piston up and down.

I guess things have moved on and modern engines do it differently.

Can SS90 explain how, we are all waiting.

.

Well Fastfred, your quite right...... round and round, up and down..... however it's not so much that those things have changed, it's more that our understandings of the effects of things like-: primary compression ratios,type of mounting systems,weights of flywheels,RPM,intended use,(even who is riding) angle of cylinders ("laydown" or "upright" cylinders) and to a certain degree....type of expansion chamber design (and even ignition type) .....have improved. And as such different balance factors are applicable.

I hope that speedpro kept his figures from the crank he did, because we can (very quickly) calculate his balance factor he ended up with (using the equation I posted last week)

Speedpro also correctly said that there is an element of "suck it and see" with balance factors.....

like many things with a two stroke engine, it's about a complete system, rather than "one for all", and experience is everything.

I have to get up early tomorrow and we are driving 200KM for the first Race meeting of the year, (some place called "Dettendorf"...thank god for GPS....)so I don't have time to elaborate, but perhaps on Sunday night I can write a few things from my experiences.
That's Monday morning NZ time, so something for the new week.

It's not exactly "revolutionary",(and I will certainly never claim the credit for these (or any other) tecniques.....I have actually found over the last few years that every time you think you have found something new, a little research shows you that someone else thought of it before you....a long time ago generally!

Like I say, this engine DOES vibrate a little (but less than the full circle crank does...which, by the way, vibrate TERRIBLY!)..........

Enjoy your weekend!

Cervus!

[bucketracer]

(60g+34g)/(60g+315g+10g)=25% (using Bucketracers suggested 3 decimal places method), other wise it would be 24.5%


Well Fastfred, your quite right...... round and round, up and down..... (using the equation I posted last week)

Just a little thing but, A+B=C is an equation a string of numbers added and divided is an arithmetic sum.

Knowing the difference is probably important, before trying to give us an insight into the science of balance factors.

SS90 which branch of classical mechanics will you use to paint the picture for us.

Will it be kinematics, which is not to be confused with another branch of classical mechanics: analytical dynamics (the study of the relationship between the motion of objects and its causes), sometimes subdivided into kinetics (the study of the relation between external forces and motion)

And just a reminder, it was not decimal places. I suggested working with the "significant numbers" just like the profesionals do, if you want accuracy in measurement and calculation.

We look forward to your insights.

[speedpro]

Balance factors - so simple on a single. A mass going up and down generating forces which we try to negate with something going round and round also generating forces. When you get down to it the whole idea is pretty stupid. It can't work except at 1 speed and on a single the rotating bit generates forces whose direction varies as the crank rotates. Engineers have lost their jobs for coming up with ideas like that. BMW had a better idea, they balanced their single with a more or less reciprocating mass.

When I balanced my MB crank on the jig I just measured the weights and divided one by the other and multiplied the result by 100 to get %. An old guy I met who used to race big singles suggested the method. If you get right into the maths it'll drive you crazy with vectors, mass, square laws, and on and on. Hence my little jig and scales. As SS90 says though, if you were to balance a TS100 motor the same as a MB100 you will get a different effect due in this case to the difference in cylinder angle. It'll still be balanced exactly the same if all the bits of metal weigh the same but once fitted to the bike it would feel different. That might be why Honda fitted a balance shaft - to get around the problem. A single is going to have forces generated at 90deg to the centre line of the bore by the crank that aren't opposed by the reciprocating forces. On the TS they are essentially horizontal whereas on the MB because of the sloping cylinder they will have a vertical component which will be noticed more by a rider.

[FastFred]

From what I can see SS90 has not brought up anything Thomas and his KISS method has not already covered here or on the ESE or can be found in Phill Irvings book.

I look forward seeing what SS90 has to offer in the way of new ideas.

.

[k14]

Can SS90 explain how, we are all waiting.
Maybe he needs to go and ask Thomas? :Pokey:

[Buckets4Me]

Jeckle and Hide
or Thomas and SS90 ??????

which one is nice and who is the prat ?
:bleh:

[sonic_v]

Well, that's what i am trying to establish some figures for...... like the figures you posted.......a "modern" TZ250 is 1.40:1......an RS125 1.33:1

From memory (I have owned and raced both these models) A 1991 TZ250B revs till 11,000 (primary compression ratio 1.40:1) a 1995 RS125R revs to 13,000 (standard, A kits more), and have a primary compression ratio of 1.33:1

Hmmmm,

I see a pattern forming here!:niceone:

Re-read Gordon Jennings chapter on Crankcase volume (he mentions the same SAE paper there)

He also gives some insight and opinion on the reasons people increased primary compressions in the first place.

Have you seen any modern literature that gives minimum figures for primary compression ratios (for different engine set ups (operating RPM,capacity exhaust design etc?)

The TZ250B v-twin yamaha give peak power at 12,000 revs/min and could produce useful power to close on 13,000. The fuel power jets did not even switch of until about 12,200 revs/min. Just concerned that you might be drawing conclusions based on 11,000 revs/min.

[SS90]

From what I can see SS90 has not brought up anything Thomas and his KISS method has not already covered here or on the ESE or can be found in Phill Irvings book.

I look forward seeing what SS90 has to offer in the way of new ideas.

.

O.K

Like I said, these aren't "new Ideas".....but it would seem that it is new to (almost, certainly not all) people who contribute to these series of threads.

I'm not really sure where to start, but I guess the best place is the confusion over the selection of balance factors (Speedpro has covered the basics of the process you can all do at home as regards to calculating the balance factor, so perhaps I should touch on the chosen factor itself)

Maybe it would be best to use the crank design I posted pictures of as an example.

Thomas has claimed that the factor I ended up with was something like 80 to 85%...... I suspect he arrived at this (incorrect) figure through lack of experience.

Here is why.

When you take a "full circle" two stroke crank (let's use a CR125 as an example in this instance, because I have personally checked this crank for this particular feature....(Honda RS125's are the same by the way) the crankwebs are in fact, not a "solid web"......they are actually "hollow" around the pin area.

This is why some two stroke cranks (Cr125, RS125) have a thin steel outer "shell"
.... that is to say...... just because the webs look like they are spun from solid stock, they are actually "cast", and the area around the pin is actually hollow.......(this is not for ALL crankwebs, but is common on most "modern" full circle crank webs....I suspect that PERHAPS MB100's are NOT like this (due to the balancing shaft), but the truth is I don't know.....If the crank is "completely round" i.e no "wasted sections" on the inside of the crank web, then chances are that it is hollow around the pin area)

My experience is if the crankwebs have a thin sheet metal out cover (rs125 Cr125 etc) then they are indeed hollow around the pin area.

K14, do you have an old RS125 crank that is ruined? maybe you could remove the tin covers from the webs and post some pics?

This, is to have a "full circle crank web", AND still maintain an acceptable balance factor, while having the "full circle" webs increase the crankcase volumes to where they want it. (by the way, this is normally quite a high primary compression ratio, as the engine's are generally designed to run over a wide RPM range (but all be it at a lower RPM) (or in the case of a commuter bike, run with out an expansion chamber (just a muffler and header pipe), both of which scenarios require "higher" primary compression ratios.

Now, the picture of the crank I posted "full circle" crank (aftermarket tuning part, made only to increase the primary compression) IS MADE FROM SOLID STOCK...(It's cheaper to manufacture)....and as such, the balance factor is 25%.....(because it has more material around the pin....it's not hollow).

If, like (most) Japanese two strokes, the webs where hollow (around the crank pin)......the balance factor would be something like 50% (near enough anyway)

Fact is, it's not, so LUCKY LUCKY me, (through experience) the very thing I need to do (increase crankcase volume (achieved by removing crankweb material)) also puts the crankshaft balance factor significantly closer to where it needs to be!

42% (with the piston assembly I am using)

Lucky me.

All I need to do, is remove the material I want (to increase crankcase volume) from around the crankpin area.

This, like I say, is why I would remove MORE material from around the crankpin, except for the fact that I fear this would weaken the assembly too much.

OR, like Speedpro correctly pointed out, add some Mallory Metal slugs to the opposite side

The end result is the same

So, there is the answer......most modern "full circle" cranks are hollow around that area.

I am not saying that ALL cranks are like that (anyone gott a full detailed view of a Suzuki GP125 crank (split from it's pin?) if it is "full circle", I would suspect that it to would be hollow in this area, if not, it will be wasted around the inside of the web (around the pin area).....

Which also helps lubricate the pin area.

If anyone has a wrecked one (CR125 or MB100 or RS125R) then perhaps they could section it right the way through..... then we will know.

Now, selection of balance factors.

That really is "suck and see"

Thomas (and others) has claimed 60-65%...... does ANYONE have data to back that up

(no internet searches please.....real data)

I have NEVER seen a factory crank with that ratio.....they are normally from 50 to 60%.

Now, (thanks again speedpro), when I stated the figure of 42% (not what I would like, but rather what I got when I had the crankcase volume where I wanted it) he correctly pointed out that such a ratio WOULD GET LESS VIBRATION THE FASTER THE ENGINE SPUN.........

Ah ha!

So, if you had a balance factor of 65%, then low RPM would be quite smooth and high RPM would vibrate more ( good for a commuter bike), and a ratio closer to 50% would be the opposite.....vibrate in the lower RPM, but smooth out at the higher RPM ( good for a Performance Two stroke)

Don't forget that a 125cc aircooled performance two stroke generally operates from 7500RPM up to say 12,000 RPM, a commuter bike from 2,000 RPM to maybe 6,000RPM

Also, as I have covered before (in the ESE thread) higher primary compression ratios (too high ratios that is) increase pumping losses of an engine (energy required to do the work) in the situtation where you have such "pumping losses", your engine is subjected to more vibration........lower the primary compression ratio....lower the losses.....less vibration (therefore a smaller balance factor can be used)

So, less primary compression means smaller balance factor.

Also, peak pressure on the piston comes into play as well.

Like I have said, it's all about a complete system.

Not "one rule for all"

As a matter of interest, Honda where using this "hollow web" system since the 70's.....

What balance factor would Thomas suggest?

PS, a google image search under "hollow crankwebs" yeilded this result......

It's FOR A CHAINSAW! (they rev a bit don't they?)

It's not what I was looking for, but huh,still worth seeing.

Hopefully someone like K14 has an old crank to illustrate my point.

YOu may also be interested K14 (and other GP125 riders, just out of interest, no good for New Zealand circuits) the picture of the second crank is an after market Rs125 Honda crank....it has no tin plates on the webs, it is a complete "full circle crank"...this is a deliberate design, and done to increase the weight of the flywheel....(it does two things for a 125 GP bike.......)

1) increases the inertia of the crank (producing more torque),
.....and
2) allows the rider to "get on the gas earlier"....

The downside is that the heavier crank is no good for "short curcuits", (like NZ...the tracks are too tight in NZ) and only of benefit when it is used on the larger tracks here in Europe...........

To get the balance factor correct, you can see that the manufacturer has added "Mallory Metal" to the lower portions of the webs.

The crankcase volume on a Honda RS125 is quite large, and when running a true "full circle crank" the ratio is around 1.38:1 (from memory)

If the crankcases on the Vespa small frame engine I put the crank in where "larger" (internally) I would have been able to leave the webs complete, and, to get the balance factor correct, added Tungsten (Mallory Metal is a free machining alloy of Tungsten) at similar points.

I think you would find that while the weight of the two cranks in the pictures I posted are different........with the addition of the Malloy Metal in the second example, the "balance factors" would be quite similar.

Balance factors are simply ratios.
It doesn't matter what the whole assembly weighs.

That's another thing all together.
The last picture is of a Ducati 748 Crankshaft..... no Mallory Metal needed!:niceone:

The principals are the same.
Oh, by the way.... none of this is new (or a secret)

[SS90]

The TZ250B v-twin yamaha give peak power at 12,000 revs/min and could produce useful power to close on 13,000. The fuel power jets did not even switch of until about 12,200 revs/min. Just concerned that you might be drawing conclusions based on 11,000 revs/min.

To be honest, I am not 100% sure ( however,I am fairly sure that my old 91 had a (factory) mark at 11,000, but I can remember revving it over that a few times, and yea, I am pretty sure it still made mumbo)

I think that it's the kitted stuff that revs to 13,000 (and then they don't last long!)

The concept was to illustrate that intended RPM is ONE factor in selecting a primary compression ratio for a particular situation, and "modern" bikes (using modern exhausts and ignitions run lower than the "old school" 1.5:1

I am not saying that ALL engines should run lower ratios (motocross bikes, commuter bikes with-out expansion chambers etc) need the smaller crankcase volumes. (higher ratios)

Similarly if you have an "old school" engine set up (high exhaust port time areas, non retarding ignition,wrong blow down times,old expansion chamber design (diffuser angle etc....) then this would be an example where something closer to 1.5:1 would be suitable.

That's my experience anyway!

[FastFred]

A lot of talk about different physical layouts of crankshafts but still no explanation or formula to explain the "Balance Factor" or how its calculated.

PS. SS90 talk does not equate to knowledge.

I am begining to suspect you don't know what a "Balance Factor" is, how to calculate it or even its purpose and as a hint it has nothing to do with primary compression ratios.

And by way of a reminder.

Just a little thing SS90, A+B=C is an equation a string of numbers added and divided is an arithmetic sum.

Knowing the difference is probably important.

[TZ350]

What balance factor would Thomas suggest?


Its not, what balance factor would Thomas suggest, its your story, what do you suggest. Do you have any idea?

.

[k14]

Yes I do have three or four old cranks lying around in the shed but don't know if I can bring myself to mutilating one. They might come in handy one day ;)

I know what you mean about the inertia, the JHA kit I bought came with another rotor that is about 5 times heavier than the standard one. Beats me if I could feel a difference though. I don't think its soley just a product of peaky engines, it's a combiniation that you get when you have a very high performance water cooled 125 running on unleaded etc. One thing you do need to be careful of is not making a crank too light (specially in a 4 stroke). You will start breaking valves if you make it spin too easily.

[speedpro]

The MB crank wheels are not the same thickness for the full circle. They are thicker opposite the big end pin. So yes they are full circle, and I suspect NOT hollow, but do have an offset weight for counterbalance. TS crank wheels are the same thickness all over but have holes drilled either side of the big end pin. Interestingly they are different sizes and I have seen somewhere that ideally the counterbalance should NOT be directly opposite the big end. Phil Irving makes a point of stressing the opposite.

I know from using my little jig and measuring a few things that it is unwise to assume balance numbers based on appearance. SS90s cut down crank has a large big end pin adding mass which is opposite the counterbalance mass of the crank.

[SS90]

A lot of talk about different physical layouts of crankshafts but still no explanation or formula to explain the "Balance Factor" or how its calculated.

PS. SS90 talk does not equate to knowledge.

I am begining to suspect you don't know what a "Balance Factor" is, how to calculate it or even its purpose and as a hint it has nothing to do with primary compression ratios.

And by way of a reminder.

Just a little thing SS90, A+B=C is an equation a string of numbers added and divided is an arithmetic sum.

Knowing the difference is probably important.

Bahahahahahhah!:rofl::rofl::killingme:killingme

I think it's the other way round.



I also suspect that you are just Bucketracer with another log in.

Are you on Prozac? You possibly should be.

Please explain how the volumetric displacement of a crankshaft does not effect the primary compression ratio.

Bahahahahahha!

[SS90]

Yes I do have three or four old cranks lying around in the shed but don't know if I can bring myself to mutilating one. They might come in handy one day ;)

I know what you mean about the inertia, the JHA kit I bought came with another rotor that is about 5 times heavier than the standard one. Beats me if I could feel a difference though. I don't think its soley just a product of peaky engines, it's a combiniation that you get when you have a very high performance water cooled 125 running on unleaded etc. One thing you do need to be careful of is not making a crank too light (specially in a 4 stroke). You will start breaking valves if you make it spin too easily.

I know what you mean about saving cranks. I used to have mine rebuilt (using the old pin an rod, so not really a full rebuild) by using the big end bearing and thrust washer from a TZ250.

I would have to agree that the gains from a heavier crank on a 125 would be "hard to detect" for most of us, but the guys right at the top seem to.

Possibly the biggest advantage would come on the bikes that make 50PS (and have a rider the weight of a small child), as such a crank would resist the tendancy to "spin up" coming out of a corner.

[SS90]

The MB crank wheels are not the same thickness for the full circle. They are thicker opposite the big end pin. So yes they are full circle, and I suspect NOT hollow, but do have an offset weight for counterbalance. TS crank wheels are the same thickness all over but have holes drilled either side of the big end pin. Interestingly they are different sizes and I have seen somewhere that ideally the counterbalance should NOT be directly opposite the big end. Phil Irving makes a point of stressing the opposite.

I know from using my little jig and measuring a few things that it is unwise to assume balance numbers based on appearance. SS90s cut down crank has a large big end pin adding mass which is opposite the counterbalance mass of the crank.

Yea, I agree, I suspect the MB100 wheels are not hollow (due to the balance weight)

As you know speedpro, a single cylinder is impossible to balance correctly, so it seems that is why it is most important to chose a factor that suits it's operating range, opposed to a compromise for the entire rev range.

What was the balance factor you ended up with?

[FastFred]

Bahahahahahhah!:rofl::rofl::killingme:killingme

I think it's the other way round.



I also suspect that you are just Bucketracer with another log in.

Are you on Prozac? You possibly should be.

Please explain how the volumetric displacement of a crankshaft does not effect the primary compression ratio.

Bahahahahahha!

Sorry SS90 but there is more than one of us who are begining to think you don't have a clue.

Your confusing the "Balance Factor" the crankshaft has been made with, with its "Physical Shape".

Physical Shape is not the same as Balance Factor.

Physical Shape has a bearing on primary compresion ratio.

Balance Factor has a bearing on how much of the reciprocating weight is counterbalanced.


And they are completetly different things!!!!!


You had better go and suck some more prosac before you get over excited and start running off at the mouth talking rubbish again.

.

[SS90]

Sorry SS90 but there is more than one of us who are begining to think you don't have a clue.

Your confusing the "Balance Factor" the crankshaft has been made with, with its "Physical Shape".

Physical Shape is not the same as Balance Factor.

Physical Shape has a bearing on primary compresion ratio.

Balance Factor has a bearing on how much of the reciprocating weight is counterbalanced.


And they are completetly different things!!!!!


You had better go and suck some more prosac before you get over excited and start running off at the mouth talking rubbish again.

.

Again.....Bahahahahahahahha!

Removing the material from the correct place of a crank does TWO things

1) it changes it's physical shape (and volumetric displacement...physical SIZE)
2) it changes it's balance factor (the factor you get depends on how much you take off, and from where)


Bahahahahahahha!

What are you not understanding?:killingme:killingme

[SS90]

Its not, what balance factor would Thomas suggest, its your story, what do you suggest. Do you have any idea?

.

Read my post again.

I suggest a ratio there.

[FastFred]

that is why it is most important to chose a factor that suits it's operating range, opposed to a compromise for the entire rev range.

SS90 you still hav'nt explained what a "Balance Factor" is and you promised you would.

[FastFred]

Removing the material from the correct place of a crank does TWO things

1) it changes it's physical shape (and volumetric displacement...physical SIZE)
2) it changes it's balance factor (the factor you get depends on how much you take off, and from where)

What are you not understanding?:killingme:killingme
Yes changing a cranks shape by say cutting a piece of it will change both its balance factor and the primary compression ratio.

What I can't understand is a mind that can't see the difference between two entirley different properties, I guess your confused by the interrelationship between them. But prosaic does that to you.

I think by now every one understands that several cranks can all have the same balance factor but different physical shapes, no biggie there.

It's changes to the physical shape not balance factor that affects the primary compression ratio.

and you still have not explained the concept of "Balance Factor". Are you sure you know what your talking about.

[SS90]

SS90 you still hav'nt explained what a "Balance Factor" is and you promised you would.


Bahahahahahahahha!:rofl::rofl::rofl:

Have you even read (and understood) the posts here in the last week?

That has already been established.

Start at the beginning.

It's all there.

[SS90]

Yes changing a cranks shape by say cutting a piece of it will change both its balance factor and the primary compresion ratio.


I think by now every one understands that several cranks can all have the same balance factor but different physical shapes, no biggie there.

It's changes to the phsical shape not ballance factor that affects the primary compresion ratio.

and you still have not explaind the concept of "Balance Factor". Are you sure you know what your talking about.

hahahahaha,

The first sentence suggests you are understanding it, you just get confused after that.

Your getting yourself confused now.

hahahahahaha,

You can change one thing (physical shape....which by the way....changes it's volumetric displacement) and that also changes it's balance factor, it just depends on where you remove (or perhaps add) the material.

What part of that are you not getting?

[FastFred]

As I said your a confused boy. Sorry SS90 up untill your latest ramblings I thought you might have something to offer about "modern" thoughts on balance factors but you can't even explain what a "Balance Factor" is.

.

[SS90]

As I said your a confused boy. Sorry SS90 up untill your latest ramblings I thought you might have something to offer about "modern" thoughts on balance factors but you can't even explain what a "Balance Factor" is.

.

Geee,

You havn't been following there have you?

I will write this REALLY SIMPLY.

Crankshaft balancing is simply the term used to describe changes made in the counterweights (webs) of the crankshaft to compensate for the weight of the moving components including the crankshaft,rod,piston,rings,gudgeon pin,clips.

The "factor" is simply a way of expressing this "counter weight" on the crank
compared to the weight of the piston rods assembly.

i.e the piston/rod assembly weighs this percentage of the crankwebs (counterweights)

What weight you chose (primarily) dictates what RPM the engine is best "balanced"

[FastFred]

.

"Yes changing a cranks shape by say cutting a piece off it will change both its balance factor and the primary compression ratio."

Then rebuilding the cut with a lighter material like devcon will restore the primary compression ratio to what it was but not the balance factor.

the ballance factor or changes to the balance factor does not affect the primary compression ratio, crank shape does.

Go on SS90 do tell us what "Balance Factor" means, have a go, define it for us.

Use a formula if you want, you know what a formula is don't you?

.

[SS90]

.


Then rebuilding the cut with a lighter material like devcon will restore the primary compression ratio to what it was but not the ballance factor.


.

Bahahahahahahha:rofl::rofl:

When did I say that?

[FastFred]

No you didn't say that, I did. You havn't sufficent insight to understand it.

Still no formula for "Balance Factor".

[FastFred]

Geee,

You havn't been following there have you?

I will write this REALLY SIMPLY.

Crankshaft balancing is simply the term used to describe changes made in the counterweights (webs) of the crankshaft to compensate for the weight of the moving components including the crankshaft,rod,piston,rings,gudgeon pin,clips.

The "factor" is simply a way of expressing this "counter weight" on the crank
compared to the weight of the piston rods assembly.

i.e the piston/rod assembly weighs this percentage of the crankwebs (counterweights)

What weight you chose (primarily) dictates what RPM the engine is best "balanced"

Getting closer.

I see you have had a quick read of Phill Irvings book but he puts it better and correctly.

You've more or less said it but lets see what you've understood.

Now tell me which is heaver, (A) the reciprocating weight of the rod piston assembly or (B) the counter weight of the crankshaft.

SS90 this is the test (A) or (B).

[SS90]

No you didn't say that, I did. You havn't sufficent insight to understand it.

Still no formula for "Balance Factor".

My god.
How old are you Bucketracer?

You are the only person on this thread that can't see that just by changing you log in name, you don't get any smarter.


I already posted the formula for calculating a balance factor.

Last week.

You pointed out that it was indeed an "arithmetic sum", not an "equation" as I had called it.

Perhaps you can be so good as to explain the breakdown of the relevent figures for us all?

I.E, what number represent what part of the engine?

You seem to be calling my experience (and intelligence) into question.

That would suggest you know what you are talking about.

Come on, don't be shy.

[FastFred]

You seem to be calling my experience (and intelligence) into question.



"Intelligence is the ability to learn."

SS90 lets test your intelligence.

So once again, which is heaver, (A) the reciprocating weight of the rod piston assembly or (B) the counter weight of the crankshaft.



(A) or (B) SS90


.

[FastFred]

.

One is a % of the other, when SS90 can correctly workout the answer to the question, he will have finaly come to an understanding of "Ballance Factors".

Well maybe he will get it or maybe not, if not, my work here is done, because you can't spend forever trying to help the terminaly stupid. I am off for a pint and to tell my brother how this went. :apint:

.

[bucketracer]

Your confusing the "Balance Factor" the crankshaft has been made with, with its "Physical Shape".

Physical Shape is not the same as Balance Factor.

Physical Shape has a bearing on primary compression ratio.

Balance Factor has a bearing on how much of the reciprocating weight is counterbalanced.

And they are completely different things!!!!!



Again.....Bahahahahahahahha!

Removing the material from the correct place of a crank does TWO things

1) it changes it's physical shape (and volumetric displacement...physical SIZE)
2) it changes it's balance factor (the factor you get depends on how much you take off, and from where)

What are you not understanding?:

SS90 in your confused bumbling way you have eloquently demonstrated that engineering is almost always a compromise, that changing one thing invariably affects something else. Like, if you change the balance factor you have to take some corrective action to maintain the same primary compression ratio. Like plugging the new balance holes or putting tin covers over the crank wheels like in the Honda RS125.

When changing the balance factor, means changing the crank shape, this affects the primary compression ratio. This is the problem of unintended consequences that comes from changes to one thing affecting another and its traps like these that all engineers before Phill Irving and every one since has had to deal with.

The unintended consequences of changes to the balance factor, affecting the primary compression ratio may be a modern problem, but SS90 there is NO so-called “Modern understanding of Balance Factors” in your posts here. But there is a lot of verbage and a few photos of cranks that have different shapes but could have the same balance factors, demonstrating what I have just been saying about the age old engineering problem of how one thing can impact on another.

Every engineer or tuner needs to be consciously looking out for how the changes they are making will affect other things in the system. There are some new traps with modern 2-strokes but the crankshaft still goes round and round and the piston up and down, basically, other than the occasional balance shaft nothing much has changed for a single cylinder, 4 or 2-stroke since Phill Irving wrote that chapter on crank balancing.



.

[saxet]

SS90 in your confused bumbling way you have eloquently demonstrated that engineering is almost always a compromise, that changing one thing invariably affects something else. Like, if you change the balance factor you have to take some corrective action to maintain the same primary compression ratio. Like plugging the new balance holes or putting tin covers over the crank wheels like in the Honda RS125.

When changing the balance factor, means changing the crank shape, this affects the primary compression ratio. This is the problem of unintended consequences that comes from changing one thing affecting another and is something all engineers before Phill Irving and every one since has had to deal with.

The unintended consequences of changes to the balance factor, affecting the primary compression ratio may be a modern problem, but SS90 there is no so-called “Modern understanding of Balance Factors” in your posts here, just the age old engineering problem of one thing impacting on another. Nothing much has changed since Phill Irving wrote that chapter on crank balancing.

.

Is'nt this what ss90 has been saying all along, are you even reading this??:eek:

[bucketracer]

Is'nt this what ss90 has been saying all along, are you even reading this??:eek:

No, I don't think so. Sure he may have talked about one thing affecting another, but the way I read it, he explains it as a modern understanding of the relationship between balance factor and primary compression ratio and that juggling the two implies a new modern thinking that makes Phill Irvings work old hat.

Where I say more correctly I think, that changes to the physical shape of the crank to achieve a different balance factor has an unintended impact on the primary compression ratio. And that juggling the two is the age old engineering problem of compromise and Phill Irvings book is not as old hat as you might think.

If I am wrong please explain it to me.

[Ned Kelly]

Which is heaver, (A) the reciprocating weight of the rod piston assembly or (B) the counter weight of the crankshaft.


(A) or (B) SS90

.


I have been looking everywhere for the answer to this. Does anyone know the answer?

SS90 help us out here. Thanks.

.

[Buckets4Me]

Geee,


i.e the piston/rod assembly weighs this percentage of the crankwebs (counterweights)

What weight you chose (primarily) dictates what RPM the engine is best "balanced"

so the crankwebs are heaver so the answer is B

thanks SS90

piston rod = 25% of crankwebs (counterweights)

[bucketracer]

so the crankwebs are heaver so the answer is B

thanks SS90

piston rod = 25% of crankwebs (counterweights)

"the crankwebs are heaver" Seriously is this what SS90 Thinks............Your not making it up?

.

[Fastborisracer]

Is'nt this what ss90 has been saying all along, are you even reading this??:eek:


No, I don't think so..

:confused::confused::confused::confused::confused: :confused::confused::confused::confused:

[bucketracer]

:doh:

My god.

How old are you SS90?

Are you the only person on this thread that can't see that just by changing you log in name, you don't get any smarter.

But I like it. :laugh:

Lets play a game where we see who can make the other look the bigest dickhead. I know your trying hard but I am winning so far.

We could even start a pole!!!!

Now lets see, we could discuss something that you don't know anything about like 2-stroke tuning and engine ballance, while you flounder through it we trade insults and the public get to vote on things like imaginative input, creative crap about modern ballance factor thinking and sheer stupidity. And along the way drop a little gem about something technicall and interesting here and there, should be fun, are you on???

Ill start, So which is heaver, (A) the reciprocating weight of the rod piston assembly or (B) the counter weight of the crankshaft.

PS Fastborishracer the public are still waiting for your answer (A) or (B) ? Mmmmm don't know do you.

And this is the crux of "Ballance Factor"

Now neither SS90 or Fastborishracer is telling us, thats not fair, them being so smart and all.

.

[bucketracer]

:confused::confused::confused::confused::confused: :confused::confused::confused::confused:

Oooops Fastboris there is a spelling mistake in your name!

Now if your going to bring a knife to a gun fight, at least have the brains to make sure its sharp first!

Sharpen up Boris

[F5 Dave]

so the crankwebs are heaver so the answer is B

thanks SS90

piston rod = 25% of crankwebs (counterweights)

The difference in weight of the crankwebs, if it was just the crankweb then it could be a consistent weight all the way around, it would rotate at any speed & as long as the piston & rod were weightless there would be no issue.

And for the love of Elizabeth, will people stop spelling You're as Your (well I've got to score points somewhere in this game don't I?:bleh:)

[bucketracer]

The difference in weight of the crankwebs, if it was just the crankweb then it could be a consistent weight all the way around, it would rotate at any speed & as long as the piston & rod were weightless there would be no issue.

And for the love of Elizabeth, will people stop spelling You're as Your (well I've got to score points somewhere in this game don't I?:bleh:)


"Respect" F5 Dave "Respect" an honest effort, a great interpretation, of someone else's crap but even better it's so so true, you're the first to score points. 3 points for spouting crap, 7 points for creativity and imagination, 12 points for knowing its crap yourself and double extra bonus points because the crap is also true and 3 points for teaching us something worthwhile (ie. stop spelling You're as Your). What a score from just two sentences, very impressed I am. :not:

[speedpro]

It seems that most people are finding it too cold to do anything constructive.

[Buckets4Me]

It seems that most people are finding it too cold to do anything constructive.

tripple points for that :jerry:

minus twice that again for not turning up sunday :2guns:

[SS90]

Sigh.

While I am finding it hard to even respond to your nonsense Bucket racer (I feel that this only encourages you) I will exapain AGAIN

First though, I have No idea who Fastorrisracer is.

You will notice his post was at 14:23 (that's 2:23PM NZ time)

Erm....that's 4:23 AM where I live...... I had been asleep for about 6 hours at that point.

I assure you I am above the kind of childish nonsense you are demonstrating.

"a modern approach to balance factors"

Ok, (again)

What is "high RPM?" 40 years ago, maybe it was 7,000 RPM, now, a tuned 125cc aircooled two stroke engine will spin to 12,000 RPM

So, on this basis alone, if a balance factor of 65% was applicable for an engine (spinning to 7,000 RPM that is), what would the factor be for an engine spinning to 12,000 RPM?

We have already established that the higher an engine spins, the lower the %age needs to be

I am sure you are unaware what the balance factor is of a 125GP bike......

it's 52%

The accepted balance factor for a modern 125cc 2 stroke, revving to 12,000 (or higher is 52%)

all the nonsense you are reading off the internet is for "general commuter items)

Tuning for speed was (thanks Kickaha) written in 1945.

RPM limits have moved on a bit since then.

You are not really folowing what I am saying, you just try to find fault with it, because you don't truly follow it and understand it.

I have been a motorcycle mechanic for 15 years.

I have a good understanding of this.

With regard to primary compression ratios having an effect on what balance factor you chose.....what do you not understand about that?

I have (several times) explained the theory of pumping losses (when the crankcase volumes are too small)

If you increase the crankcase volume, the engine operates at a higher RPM, therefore, you need to have a lower balance factor (that if the engine was operating at a lower RPM)

What is so hard to understand?

[bucketracer]

I have been a motorcycle mechanic for 15 years.

I have a good understanding of this.


So you say SS90 but it's just Talk Talk Talk

So once again, when a balance factor is greater than 50% which is heaver, (A) the reciprocating weight of the rod piston assembly or (B) the counter weight of the crankshaft.

(A) or (B) SS90

Its the crux of the whole thing and realy simple.

And SS90 although I admire the effort you have been putting into keeping up the pretence of knowing something.

If you can't say (A) or (B) and get it right you know jack shit!

Its such a simple question, like "is a spark plug a left or right hand thread". Something a motorcycle mechanic thats been in the trade 15 years and has the understanding of "Balance Factors" that he claims, should be able to answer easy piesy.

.

[Skunk]

Someone just answer the fucking question so I can learn something instead of this mindless one-up-man-shit!

[bucketracer]

Yes answer the question SS90.

[TZ350]

Sorry if I am stealing someones thunder but:-

The answer is (A) as the counter weight only counters a % of the reciprocating weight and is lighter than the reciprocating portion of the rod/piston assembly.

Yes, the counter weight portion of the crankshaft is the lighter of the two.

As an example, a balance factor of 65% means that the counter-weight portion of the crankshaft counter weighs only 65% of the reciprocating mass of the rod/piston assembly.

The Balance Factor could be anything, 25% 48% 50..............65%......85% whatever you chose/works for that engine/frame/rev's/and everything else combo.

The counter weight portion of the crank may or may-not necessarily be dead opposite the bigend.

Interestingly Phill Irving suggests a balance factor of 66% as a good place to start and the 2009 Kawasaki KX250F and KX450F (4-Stroke) Motocrossers both have Balance factors of 60%.

2009 KX250F
Engine Displacement: 249cc
Max Horsepower: 32.8 HP @ 12,200 rpm
Max Torque: 17.2 lb-ft @ 8400 rpm


Remember you heard it from TZ350 first.

.

[Buckets4Me]

all the nonsense you are reading off the internet is for "general commuter items)



thats what i thought we where using to build our buckets
not 14000 rpm rs125 hondas or Aprillia gp bikes :yes: :bash:

[k14]

all the nonsense you are reading off the internet is for "general commuter items)



thats what i thought we where using to build our buckets
not 14000 rpm rs125 hondas or Aprillia gp bikes :yes: :bash:
No what everyone is doing is taking a "general commuter item" and trying to turn it into a 14000rpm honda or aprilia gp bike. So taking the tuning data from one of those and applying it to what we have is the already proven method. Of course there are compromises but those bikes are the benchmark and by copying as many aspects of them as possible everyone hopes to end up with a fast bike!!

[FastFred]

No what everyone is doing is taking a "general commuter item" and trying to turn it into a 14000rpm honda or aprilia gp bike.

Very much like picking up an ugly one then! and drinking enough piss untill they look good. :drinkup: SS90 I've got the money honey if you got the time! I'm not fussy. :buggerd: you know you would like it, don't you! and wear that little black number I saw you in last week.

[F5 Dave]

"Respect" F5 Dave "Respect" an honest effort, a great interpretation, of someone else's crap but even better it's so so true, you're the first to score points. 3 points for spouting crap, 7 points for creativity and imagination, 12 points for knowing its crap yourself and double extra bonus points because the crap is also true and 3 points for teaching us something worthwhile (ie. stop spelling You're as Your). What a score from just two sentences, very impressed I am. :not:
What? No rep bling awarded?:sunny:

sheesh I need to get a more fanatical following that will do my bidding.

Perhaps overthrow a building tenancy committee in a hostile take over. Then Austria.

[F5 Dave]

Someone just answer the fucking question so I can learn something instead of this mindless one-up-man-shit!

I've just worked it out. SS90 = Winston Peters.

Well think about it; - can't answer a straight question in anything other than "I've already answered that question" or dodging around it with another supposition.

I mean it makes sense, he turned up at about the same time, cagey about his identity. . . Well?

I hope you've given that ministerial car back buddy!

[SS90]

Sorry if I am stealing someones thunder but:-

The counter weight portion of the crank may or may-not necessarily be dead opposite the bigend.


.

That brings up a (slightly) different part of the subject.

There are a few engineers who chose the point where there balance the crank

i.e what position the crankpin is at (looking at it from the taper sider, what degree is it at.....12 oclock, one oclock, sometimes two oclock.

It depends on who you talk to. It seems common practice that MOST people balance it at the 12 oclock position, yet having ridden bikes with both approaches, I have never noticed a difference.

I suspect it is because a single cylinder vibrates so much anyway, that a slight change in either direction is unnoticed.

This one was checked in the 12 oclock position.

As a matter of interest with the subject of getting the correct factor on the crank I made (52%) I would have to add 35gm's to the counter weight (webs) or remove weight from the crank pin. (drilling the centre),

I suspect that would be courting disaster though.

Other than speedpro's jig set up, there is also dynamic balancing....... the advantage of dynamic balancing, is that, for example, on the "static" set up (per Speedpro's example) you can only add (or subtract) weight from the webs in an approximate fashion...... (you just have to do your best to add/remove it as evenly as possible from each side of the webs.

If you don't take/add the weight evenly from each side of the web, you get "twist" in the webs as they spin (because they in turn are out of balance with each other)

This is what is termed "rocking couple"

Having a dynamic balancer, enables you (via computer controlled measurements) to remove/add weight as is needed, evenly from the webs.

It doesn't make any difference to the overall balance factor, but if the webs are badly out of balance with each other, the result is "twisting" of the webs, and before too long, the webs simply "twist off"

I have seen this on a very high performance engine (with extremely light crank)

It is also a good idea to put your flywheel on when measuring your balance.... be it static or dynamic

If you take it to a machine shop now days, chances are they will have a dynamic balancer, static is quite labour intensive.

Kind of like a tyre balancing machine compared to an axle stand, the result is more or less the same, but the machine does it faster and more accurately, as well as the operator needs less training.

[SS90]

No what everyone is doing is taking a "general commuter item" and trying to turn it into a 14000rpm honda or aprilia gp bike. So taking the tuning data from one of those and applying it to what we have is the already proven method. Of course there are compromises but those bikes are the benchmark and by copying as many aspects of them as possible everyone hopes to end up with a fast bike!!

That's pretty much as I see it as well.

Converting a road bike to a race bike does suggest there is a logical pattern to follow.

[Buckets4Me]

I've just worked it out. SS90 = Winston Peters.

Well think about it; - can't answer a straight question in anything other than "I've already answered that question" or dodging around it with another supposition.

I mean it makes sense, he turned up at about the same time, cagey about his identity. . . Well?

I hope you've given that ministerial car back buddy!

is this another whine gate ?????

[Yow Ling]

2009 KX250F
Engine Displacement: 249cc
Max Horsepower: 32.8 HP @ 12,200 rpm
Max Torque: 17.2 lb-ft @ 8400 rpm


Remember you heard it from TZ350 first.

.

Interesting figures there, Kawasaki should use vespa engines, cos they make 25 to 30ps from 140cc, maybe they havnt got the whole swirl pattern thing yet.

[Buckets4Me]

Interesting figures there, Kawasaki should use vespa engines, cos they make 25 to 30ps from 140cc, maybe they havnt got the whole swirl pattern thing yet.

it's 125 cc you nob havent you been reading what SS90 posts

it's not a 182 big bore kit on the vespa and it's still got a 24mm carb :bash:

[SS90]

it's 125 cc you nob

Welcome to the "Real World"

It is certainly not a Vespa, but it is made in Europe, and I did spend the last 2 days in the factory.

Lich ich mein arsh.

[SS90]

Oh, and by the way, one is for the road, and one is for the street........one is "Membrane Induction" and one is "Dreh Schiebe"

One is for the road (prototype) and one is for 125 GP....

[SS90]

Havn't seen this in Vietnam?

YOU?

[F5 Dave]

No doubt they were asking for your advice & you were telling them how they were doing it all wrong.:whistle:

Why are you posting with Germany quotes when you know most people can't read it? Does it make you feel superior? I'm sure Thomas could post in Vietnamese & few here would be able to translate it. Well, not without Babelfish.

[SS90]

No doubt they were asking for your advice & you were telling them how they were doing it all wrong.:whistle:

Why are you posting with Germany quotes when you know most people can't read it? Does it make you feel superior? I'm sure Thomas could post in Vietnamese & few here would be able to translate it. Well, not without Babelfish.

That's the funny thing, where is Thomas?....one monment he is all things amazing, then he is only the guy who makes jigs for balancing....

Am I the only Kiwi in the world who thinks that "Thomas" is just a name for something that Teezee found on google last night?

[k14]

Welcome to the "Real World"

It is certainly not a Vespa, but it is made in Europe, and I did spend the last 2 days in the factory.

Lich ich mein arsh.
The first pic is a RSW aprillia (was the works bike but they changed in 07 I think) the second is an RSA. Could be smiths, simons, or someones from last year. They changed the configuration of the engine quite majorly. The RSA has the carb in the "normal" place for a reed valve inducted engine (ala Honda RS125, Yamaha TZ125) but it is still rotary valve induction. There is a bevel gear that runs it apparently. That engine (I'm told, info on this stuff is very hard to find!) is designed and built by derbi for aprillia. So sort of makes a mockery of having a "derbi" and "aprillia" team fighting for the manufacturers championship in 125GP. They are both owned by the same company.

Below is talmacsi's bike from Philip Island in 07. Its the "old" RSW that he won the world championship on. Notice the airbox comes in the side to the traditionally mounted carb position for a rotary valve 2 stroke. I was told the reason they changed the engine layout was to get a better flow through the airbox? I doubt that was the only reason but it certainly makes the whole bike more symmetrical.

[SS90]

The first pic is a RSW aprillia (was the works bike but they changed in 07 I think) the second is an RSA. Could be smiths, simons, or someones from last year. They changed the configuration of the engine quite majorly. The RSA has the carb in the "normal" place for a reed valve inducted engine (ala Honda RS125, Yamaha TZ125) but it is still rotary valve induction. There is a bevel gear that runs it apparently. That engine (I'm told, info on this stuff is very hard to find!) is designed and built by derbi for aprillia. So sort of makes a mockery of having a "derbi" and "aprillia" team fighting for the manufacturers championship in 125GP. They are both owned by the same company.

Below is talmacsi's bike from Philip Island in 07. Its the "old" RSW that he won the world championship on. Notice the airbox comes in the side to the traditionally mounted carb position for a rotary valve 2 stroke. I was told the reason they changed the engine layout was to get a better flow through the airbox? I doubt that was the only reason but it certainly makes the whole bike more symmetrical.

<table style="width:auto;"><tr><td><a href="http://picasaweb.google.com/lh/photo/WCP5CiQLbfbYe9cjIwasVA?feat=embedwebsite"><img src="http://lh6.ggpht.com/_mAtAq5AlxcM/RyDxWNzRZyI/AAAAAAAAAJM/geqYzrDrZrQ/s144/Image063.jpg" /></a></td></tr><tr><td style="font-family:arial,sans-serif; font-size:11px; text-align:right">From <a href="http://picasaweb.google.com/k14.nzl/MotogpPI07?feat=embedwebsite"></a></td></tr></table>

Well done man!

Hope yourinjury is coming on well.....

How about these?

[SS90]

I have more.....come on! give me something "new".......

[Buckets4Me]

I have more.....come on! give me something "new".......

them there fighting words :zzzz:

dont look much like buckets to me
but then I guess we could rip the engine out and start again :2thumbsup

[SS90]

them there fighting words :zzzz:

dont look much like buckets to me
but then I guess we could rip the engine out and start again :2thumbsup

Gaa Gaaa

I'm sorry what?

I just was choking on some Vietnamese.......

Cough couch...... Spit.......

Say that Again?

[Buckets4Me]

you could rip the engine's out and start again !!!!

[Sketchy_Racer]

Your a cock SS90. When you first started posting you seemingly knew what you were on about and were keen to share your thoughts, now you've just turned into an ego stroking wanker. Fuck off unless your going to have good input on these forums not this chilidish crap you're spouting now.

[Buckets4Me]

:dodge::buggerd::lol:

[Skunk]

You must spread some Reputation around before giving it to Sketchy_Racer again.

[F5 Dave]

C'mon Sketchy, that's no way to talk.

"You're" is the correct abbreviation for "You are" :whistle:

[Buddha#81]

Your a cock SS90. When you first started posting you seemingly knew what you were on about and were keen to share your thoughts, now you've just turned into an ego stroking wanker. Fuck off unless your going to have good input on these forums not this chilidish crap you're spouting now.


Come on Sketchy, tell us what you really think!:dodge: What side of bed did you get out of?:angry2:

[Sketchy_Racer]

Come on Sketchy, tell us what you really think!:dodge: What side of bed did you get out of?:angry2:

Haha must be the "I can't be bothered with childish bullshit side"

[nudemetalz]

Me thinks Sketchy's ready to race a four-stroke bucket.... :lol: :calm:

[Buckets4Me]

Gaa Gaaa

I'm sorry what?

I just was choking on some Vietnamese.......

Cough couch...... Spit.......

Say that Again?

and again you could rip the engine out and start again

by the way I'm not sure how you do it over there
but swallow it's rude to spit :lol:

[FastFred]

Gaa Gaaa

I'm sorry what?

I just was choking on some Vietnamese.......

Cough couch...... Spit.......

Say that Again?

Thomas, a bit of a mouthfull SS90?

If you'er giving a bit of oral, remember it shows class to swallow, don't spit. only cheep paid-fors spit.

.