ESE's works engine tuner

[Frits Overmars]

I know it doesn't answer your question, but when TeeZee tested his 24 against a 30 in a back to back test. The 30 didn't make anymore power than the 24 and so he thought that meant the 24 could do better yet as it must be something else holding the engine back.I would think so too. Take a look here: http://www.youtube.com/watch?v=ju2X9OVEvQw&feature=youtu.be
That's a 50 cc engine with a 32 mm carb. Over 20 rear wheel HP, outstanding throttle response (it lapped the entire field on tight kart tracks).
But don't be deceived by the video: this is a reed valve engine! There is a rotary prototype version that gives over 1 HP more....

[wax]

Thats impressive

[wobbly]

Remember TeeZee I said agaes ago that I doubted that the 24mm carb would end up being the final restriction to power in the 125 Aircooled.
Based on the fact that 125 kart engines make mid 40Hp at the sprocket, low 40s RearWheel using a 30mm.
I would say that untill you have a cylinder that replicates the scavenging efficiency of the Aprilia, then you have plenty of work to do without worrying about the carb or CVT technology.

[TZ350]

Yeah i was surprised..... but then thought, well everything else on the engine was optimised for the 24mm carb anyway. I then assumed it was not really persevered with either. So how many runs and combination were actually tried?


The inlet from the manifold rubber to the rotary valve port and the port itself are optimized for 31mm. Both the 24 and 30 carb taper out to 31mm on the engine side.

The 24 has of course had a lot of dyno time. For the test the ignition and everything else was left the same as the 24 but the 30 ran reasonably Ok with the 24's jetting and was given sufficient runs to find the main jet that gave best power.

Interestingly the 30 required a much smaller main jet than the 24.

[Shorty_925]

The full set of results from the 1st round of the Pacific Club North Island Series and the Two Hour including lap times.

Do you have the b-grade laptimes from Saturday's racing?

[F5 Dave]

. . .Interestingly the 30 required a much smaller main jet than the 24.

Which makes me wonder if the test was repeated with another air jet/main combination? just a thought.

I'm still confused by my 24, 26, 28mm mikuni flatslide tests on my 1/2 piston port 50, where the 28 outperformed every carb (manifold was 26mm for test), 24 almost made same peak & 26 was worse everywhere.

I had hoped to find a kart track small carb setting & a long track carb. Just proves testing is always required. Something it didn't like about the 26 despite trying mains up & down. Piston port/ reed meant it wasn't particularly matched to a particular carb size.

In the end pwk better all round so a mute point.

[TZ350]

Do you have the b-grade laptimes from Saturday's racing?

Down load the PDF's and I think they are on page two.

[TZ350]

Which makes me wonder if the test was repeated with another air jet/main combination? just a thought.

It wouldn't matter as far as max power was concerned, as a mis match between main and air correction would only mean that it would be mixture correct at one end or the other of the power curve but not both. And by adjusting the main you can force it to be correct at the top for max power.

Optimum main jet and air correction will have the mixture pretty good at both ends.

For the test I was only interested in max power so fiddled about with the mains on the 30mm carb (which had been fitted with the 24's jets et all) until I found the sweet spot and as luck would have it, it looked good through the whole range.

I think the telling thing is the torque curves, they overlay each other very closely, and that suggests to me the engine ingested and retained the same amount of fuel/air whether it was running with the 24 or 30mm carb and this points to the scavenging of combustion products and retaining of fresh mixture as being the real issue at this point and not the carb size.

[Shorty_925]

Down load the PDF's and I think they are on page two.

only 1 page per pdf.

[TZ350]

273984

:facepalm: .... looks like I have made a bit of a blue and only have the B grade superpole times, sorry.

[TZ350]

... I doubted that the 24mm carb would end up being the final restriction to power in the 125 Aircooled.

Yes it looks that way.

[F5 Dave]

It wouldn't matter as far as max power was concerned, as a mis match between main and air correction would only mean that it would be mixture correct at one end or the other of the power curve but not both. And by adjusting the main you can force it to be correct at the top for max power.
. . ..
Yeah that's what I thought, but that doesn't explain why my 26 was worse everywhere, perhaps in a finikity (peaky) 50 it wouldn't pull through cleanly if the initial air mix was so far out. A result isn't always conclusive, one has to consider if there was an issue with the question or the test plan. and maybe there isn't.

[TZ350]

For those interested in such things, its not the top gear ratios that make the GP gearbox difficult but the lower ratios. 1st and 2nd are to low for an already geared down bike on a tight track.

An early 5 speed TS gear box can be modified to fit a GP by shortening the clutch input shaft and modifying the GP gear selectors buy building two of them up on the outside of the forks to fit the sliding dogs and opening up the ID of the other to clear its dog.
273987

Red Line is the standard Suzuki GP125 gear box.
Blue Line is the standard Suzuki TS125 gear box.
Purple line is the TS Box with modified gears, the different size gears can be made to fit by modifying the shape of the teeth.

A std TS gearbox suits a GP very nicely on a long track and a modified one works well on a short track.

[Buckets4Me]

Are you kidding hole-shots is what the cvt will give you.

The cvt is a weapon off the line. We were up against 85cc cr powered race bikes. You would holeshot them from back on the 2nd row.
I know mount wellington track I used to race kt100s on there. The cvt anillate will the gearbox bike into the top corner and you will end up playing from then on in.

You have to remember that you tune the cvt for the power of your engine so it will do both haul out of corners as well as off the line.
You can hold your engine on its power peak the entire track and at any speed if you can make the corners.

Your sitting on the power peak the whole time. If you tune a cvt wrong its easy to hold it on it the down slope of the rising slope as well and make a 30hp engine go like a 5hp engine if that where your holding the revs.

It would go great on the long tracks you would just have to change the sprockets on the chain. But that would be the same for the geared bikes

http://www.youtube.com/watch?v=x3UpBKXMRto

Awesome in the rain due to the smoothness as well. And it is new zealand after all. its going to rain

thats the problem you cant make the corners at Mt Wellington ( I can do 26's in a 125 rotax cart) but only manage 35's on the bike)
as for hole - shots I dont think TZ is all that bad at it. But the clutch gets a hiding

[cotswold]

Do you have the b-grade laptimes from Saturday's racing?


32 seconds or there abouts, bit disappointing as I had 30 bhp to play with ( do late 31's on Johns standard fxr )

[richban]

I saw a 1.5 hp gain swapping from a 30 to 32 on my bike with no drop in the mid range.

[TZ350]

yeah i was meaning is you have spent a lot of time with your engine tuning with the 24mm choke carb.
so it doesn't hugely surprise me that you didn't obtain instant results with a larger choke carb.

Yes ... it was just a quick test to get some idea if the 24 was choking it.


Its still hugely impressive i can remember someone saying no air cooled 125 will obtain more than 24HP with a 24 mm carb lol

And yes ... that is the problem with reliying on ones own real life experance and all that, because by definition its limited, I think researching everything you can and a bit of intelligence expands whats possible beyond what has already been done. Happy to be proved wrong of course.

[bucketracer]

the real irony is when the individual slams doing wide ranging research then spends so much time on the net pushing their own opinions....... i am eternally grateful Frits and Jan, Wob etc spent their time more constructively giving away there hard gained knowledge so freely ..........

Watching SS90's recent exchange with Wax, which seems to have exposed some gaps in SS90's industry knowledge and that leaves me thinking that poor old SS's real life experience and all of that has let him down a little bit.

[husaberg]

Teasing apart, it is my considered opinion that shiftboxes would have disappeared decades ago if the FIM hadn't blocked their development.


I have several knowledgeable people make similar arguments Frits, but I have never seen this in action

I wonder myself how much more knowledgeable than Frits opinion he really needs.............
How can Frits somehow lacking in "industry experience"
i also assume he has sought out some pretty clued up individuals for the CVT on the FOS concept engine. AS well as drawing own his own experience

Watching SS90's recent exchange with Wax, which seems to have exposed some gaps in SS90's industry knowledge and leaves me thinking that pore old SS's real life experience and all of that has let him down a little bit.




And yes ... that is the problem with reliying on ones own real life experance and all that, because by definition its limited, I think researching everything you can and a bit of intelligence expands whats possible beyond what has already been done. Happy to be proved wrong of course.

the real irony is when the individual slams doing wide ranging research then spends so much time on the net pushing their own opinions.......
i am eternally grateful Frits and Jan, Wob etc spent their time more constructively giving away there hard gained knowledge so freely and so much time answering questions. yet are always so modest and nonjudgmental of others..........esp in-spite of their success.... Make you wonder really...........


The inlet from the manifold rubber to the rotary valve port and the port itself are optimized for 31mm. Both the 24 and 30 carb taper out to 31mm on the engine side.

The 24 has of course had a lot of dyno time. For the test the ignition and everything else was left the same as the 24 but the 30 ran reasonably Ok with the 24's jetting and was given sufficient runs to find the main jet that gave best power.

Interestingly the 30 required a much smaller main jet than the 24.

yeah i was meaning is you have spent a lot of time with your engine tuning with the 24mm choke carb.
so it doesn't hugely surprise me that you didn't obtain instant results with a larger choke carb.
i would have thought it may have obtained a little more past peak power but then again i guess it was again optimized for its rev potential anyway as it was. Its still hugely impressive i can remember someone saying no air cooled 125 will obtain more than 24HP with a 24 mm carb
lol

[Buckets4Me]

<iframe width="560" height="315" src="http://www.youtube.com/embed/8MAqwElM18g" frameborder="0" allowfullscreen></iframe>

[husaberg]

ouch............

[speedpro]

It's been bugging me. Frits said about a CVT used on a race bike that instead of using regular curved slots in the rear pulley that the slots should be perpindicular. I can visualise how the curved slots type of variator transmission works. With straight slots the rear pulley will only be affected by the centrifugal force on the rollers at the front working against the spring at the back and there will be no response to load. It will therefore be purely speed sensitive. I have trouble seeing how it will maintain an engine at a more or less fixed RPM though. What I envisage is the ratio increasing as the engine rpm is increased. I may just be having trouble getting my head around it but it seems to me that the slots would have to be curved to make it load sensitive for it to work.

I have thought it would be better to replace the contra spring with some sort of hydraulic cylinder and control that with the ECU. The hydraulic cylinder could have a small bleed to allow it to leak down, simulating a weakening spring, thereby allowing the CVT ratio to rise, or, as the ECU detected engine revs below set rpm with TPS indicating an open throttle the pressure could be increased using a PWM controlled valve making the cylinder force the rear pulleys closer pushing the CVT to a lower ratio. The hydraulic hose would fit to the end of the shaft with the clutch on it and the fluid under pressure fed through drillings to the cylinder in place of the contra spring. This setup would use straight perpindicular slots and the ECU could contain a map to make the CVT do whatever you wanted. Only a small oil pump would be required as the cylinder volume would be small and the amount of movement would only be 5mm or so. This would only need small volumes of fluid to be pumped to control the CVT.

[husaberg]

It's been bugging me. Frits said about a CVT used on a race bike that instead of using regular curved slots in the rear pulley that the slots should be perpindicular. I can visualise how the curved slots type of variator transmission works. With straight slots the rear pulley will only be affected by the centrifugal force on the rollers at the front working against the spring at the back and there will be no response to load. It will therefore be purely speed sensitive. I have trouble seeing how it will maintain an engine at a more or less fixed RPM though. What I envisage is the ratio increasing as the engine rpm is increased. I may just be having trouble getting my head around it but it seems to me that the slots would have to be curved to make it load sensitive for it to work.

I have thought it would be better to replace the contra spring with some sort of hydraulic cylinder and control that with the ECU. The hydraulic cylinder could have a small bleed to allow it to leak down, simulating a weakening spring, thereby allowing the CVT ratio to rise, or, as the ECU detected engine revs below set rpm with TPS indicating an open throttle the pressure could be increased using a PWM controlled valve making the cylinder force the rear pulleys closer pushing the CVT to a lower ratio. The hydraulic hose would fit to the end of the shaft with the clutch on it and the fluid under pressure fed through drillings to the cylinder in place of the contra spring. This setup would use straight perpindicular slots and the ECU could contain a map to make the CVT do whatever you wanted. Only a small oil pump would be required as the cylinder volume would be small and the amount of movement would only be 5mm or so. This would only need small volumes of fluid to be pumped to control the CVT.

he said axial..... i am not sure but if you go though my links there is something about a curvature and step where and profile changes i am not sure if that helps though. But he mentioned wiuthout the curved slots it then needs a much stronger spring which i guess is a result of not using the curved slots and it then relies heavily the spring pressure to work.

[wax]

Alot of scooters have a angle change in the ramp this allows them to upshit fast in the last half of there speed increase. This means that the revs drop and it makes for nice smooth runing road scooter. Straight cut ramps on the torque driver, Not straight up and down but a straight slot hold the engine rpm at set point ( hopefully max power).
the curve makes it very hard if not impossible to get this right as it changes the torque drivers effect on the spring and also the rate at which it changes up.

The ultimate goal is to have no variation in rpm from the start to the finish of the speed run. This cant happen in reality as once you get to the top of the variator the engine will have to over rev as there is no more gears to throw at it. I also set my clutches to come in right on the power band and this tends to flare the clutch a bit as you gas it up hard in a take off. But it does make them get off the line hard.
You can put a bigger sprocket on the front of the bike and there for keep the variator from making it to the top as soon this will hold the bike on the power longer asuming you have the power to pull the high speed

[Frits Overmars]

Frits said about a CVT used on a race bike that instead of using regular curved slots in the rear pulley that the slots should be perpindicular.I said axial. But from the rest of your post I gather that you too meant axial.
With straight slots the rear pulley will only be affected by the centrifugal force on the rollers at the front working against the spring at the back and there will be no response to load. It will therefore be purely speed sensitive.Right

I have trouble seeing how it will maintain an engine at a more or less fixed RPM though. What I envisage is the ratio increasing as the engine rpm is increased.Right again. There has to be a small rise over the rpm range, maybe 200 rpm, for the primary centrifugal governor to cover the entire ratio range.

I have thought it would be better to replace the contra spring with some sort of hydraulic cylinder and control that with the ECU...........It might even work. But I'd like to remind you of the KISS-principle: keep it simple, son.
There used to be (and maybe still is) a set on the market to replace the curved dish plus rollers in the primary pully of a Piaggio scooter with a thrust bearing on a ramp, very smartly controlled by the electric starter motor that lives there anyway. It was even possible to still start the engine electrically. This set was Italian-made but I don't remember the name; I saw it about ten years ago.
A button on the handlebar gave the opportunity to select seven ramp positions, so you could 'shift' at will, like with a priceless seven-speed seamless shift box. But it would be logical and fairly simple to let an ECU continuously control that ramp.
Come to think of it: the Suzuki Burgman 400 scooter has something similar.....

[Buddha#81]

<iframe width="560" height="315" src="http://www.youtube.com/embed/8MAqwElM18g" frameborder="0" allowfullscreen></iframe>

Fark what a mess.........even guys wandering off the track as the leaders come round for their first lap. Lots of ways for that to go real wrong!

[Bert]

Fark what a mess.........even guys wandering off the track as the leaders come round for their first lap. Lots of ways for that to go real wrong!

my god... :facepalm::shit:
That requires a bit of a re think for future application.

[Henk]

my god... :facepalm::shit:
That requires a bit of a re think for future application.

Has been discussed. From now on the "pusher" will only be able to hold the bike until the rider grabs it. Will give the two strokes a bit more of an advantage and will probably spread the feild out a bit more, not a bad thing really.

[jasonu]

>

What a cluster fuck! How come the bike holders are allowed to help push and thus end up in the middle of the track? The 2hrs I have been involved in had the holder standing on the grass and HOLD the bike, and the rider did all the pushing.

[TZ350]

How come the bike holders are allowed to help push and thus end up in the middle of the track? The 2hrs I have been involved in had the holder standing on the grass and HOLD the bike, and the rider did all the pushing.

This pushing thing is the way I remember them but I have heard that is going to change for next year.

The way I hear it, the riders are going to have to push start their bikes themselves, with no kick or electric starters allowed.

Guess how easy it is to push start the Beast. ...:D

[kel]

How come the bike holders are allowed to help push and thus end up in the middle of the track?

Because FXR's hate Le Mans starts, they're complete pigs to push start.
So from next year the 2 strokes will bolt while FXR riders collapse from exhaustion :killingme
I just hope they're off the track when we come round to start the next lap.

[Pumba]

Because FXR's hate Le Mans starts, they're complete pigs to push start.......

Bull Shit

Ok I admit that a few years ago in a 2hr JC pushed me for a bloody long time, but that carb was a POS and I never got it to run rigth off the bottom. Get the carb set up right and they will fire everytime. Shit the only reason mine still has the kick start i for convenience

[jasonu]

This pushing thing is the way I remember them but I have heard that is going to change for next year.

The way I hear it, the riders are going to have to push start their bikes themselves, with no kick or electric starters allowed.

Guess how easy it is to push start the Beast. ...:D


Because FXR's hate Le Mans starts, they're complete pigs to push start.
So from next year the 2 strokes will bolt while FXR riders collapse from exhaustion :killingme
I just hope they're off the track when we come round to start the next lap.

I competed in 3 or 4 2hrs in the mid 90's and never was the holder allowed to push. Shane Husband used to get his CB125 twin away as good as anyother bike and some of the 2 smokers were pigs to get going. The start is part of the race and builders should make sure their machine will actually start and the rules should not be changed to accomodate a certain group. Plus it is fucking dangerous as the video showed (and it could very easily have been a lot worse too). Just my opinion.


Bull Shit

Ok I admit that a few years ago in a 2hr JC pushed me for a bloody long time, but that carb was a POS and I never got it to run rigth off the bottom. Get the carb set up right and they will fire everytime. Shit the only reason mine still has the kick start i for convenience

Well there ya go then...

[Kickaha]

Because FXR's hate Le Mans starts
I actually found them bloody brilliant when I had mine

Ignition on and in gear, while swinging the leg over you pull in the clutch and hit the starter and away you go, simple really unless of course you're a fashion lemming and have removed all that shit :whistle:

[Yow Ling]

Too lazy to do much intelligent stuff today, messed around in the shed
274025
Im starting to like these RG150's, so versatile , make em into buckets, cheap to buy, plentifull
274026
Mmm another one, famous one
274027
Waiting for its engine from foreign lands
274028
Removing the sleeve from RG barrel, little known fact , RG150 sleeve weighs 600g
274029
Dyno the weedeater
274030
A massive weight I found hiding behind the flywheel in a RG

[husaberg]

Not as productive as Mikes day (WC champs at Hokitika) not a stella day for the nipper either. taken out 3 times from behind
I did find this stuff yeah it might not be as tunable as the DR...HIT...combo or work as well (i have no idea but i guess WAX will .........)

but interestingly simple..........

http://csimg.shopwahl.de/srv/DE/290339480168jc607fsevo3r/T/340x340/C/FFFFFF/url/variator-transversal-jcosta.jpg

http://www.youtube.com/watch?v=y-QqHE0bNjw&feature=player_detailpage
http://www.youtube.com/watch?v=y5DdUW95l0w&feature=player_detailpage

http://burgmanusa.com/forums/viewtopic.php?t=23707

http://advrider.com/forums/showthread.php?t=780204

[wax]

I have seen those but never played with it. It shows promise but cant really offer to much on it. I spent the day tuning my scooter. It wants to rev to 12900 I hope it can handle it for 24 hours lol

[husaberg]

I spent the day tuning my scooter. It wants to rev to 12900 I hope it can handle it for 24 hours lol

So what was actually wrong with it?

[wax]

So what was actually wrong with it?

With the variator or my scooter

[husaberg]

Anyone possibly help. I have built my new race engine. It will idle just fine but it will not rev. as soon as I get above 7-8000 rpm it splutters and just pums black goo out the exhaust. I have had a look at the timing and it running 15 down low then it goes to 30 till about 9 and drops back to 15 from 10 onwards. Even with no load on it should still rev cleanly past these points.
Im desperate and very stressed as I have a race in the next few weeks
I have tried 2 different carbs on it with no change


With the variator or my scooter

The engine?

[wax]

Oh the msd registers the length of the pickup lump for you and it had it 10 degrees wrong and so it was stuffing the timing up. I calculated it with a degree wheel and entered it and away we went

[Buckets4Me]

I actually found them bloody brilliant when I had mine

Ignition on and in gear, while swinging the leg over you pull in the clutch and hit the starter and away you go, simple really unless of course you're a fashion lemming and have removed all that shit :whistle:

sounds like an instant black flag to me :motu: you cheater

[chrisc]

Most likely watched before by those who visit this thread but I enjoy watching these old races again anyway


http://www.youtube.com/watch?v=NZzafYmwUT4

[bucketracer]

Take a look here: http://www.youtube.com/watch?v=ju2X9OVEvQw&feature=youtu.be
That's a 50 cc engine with a 32 mm carb. Over 20 rear wheel HP, outstanding throttle response .....

<iframe width="560" height="315" src="http://www.youtube.com/embed/ju2X9OVEvQw" frameborder="0" allowfullscreen></iframe>

Very impressive, I like the starting technique too.

[F5 Dave]

What a cluster fuck! How come the bike holders are allowed to help push and thus end up in the middle of the track? The 2hrs I have been involved in had the holder standing on the grass and HOLD the bike, and the rider did all the pushing.

Seems that what was learnt was forgotten. That could have lead to a cracked skull. Bike holders shouldn't be allowed to leave the grass. That's the rule in welly. No pushing.

[bucketracer]

Bike holders shouldn't be allowed to leave the grass. That's the rule in welly. No pushing.

A little bird has told me that things are going to change and Bike holders won't be allowed to leave the grass next year.

[wax]

http://www.youtube.com/watch?v=BbUllp6ap-A&feature=youtu.be

This is the 50cc scooter on a shake down for the 24hour

[chalkie]

question for anybody who has an opinion,
if you cylinder only has a single exhaust port,how soon would you make the transition from the oblong
shape to the round header diameter?
the port from piston face to start of stub is 20mm,also ,would the aprillia flange missmatch work on a single port?
finally,is there an optimum angle for the exhaust port as it exits the cylinder ?
have been reading this forum for a while now,guess that Frits & Wob would be the guys in the know!
thanks in antiscipation,
chalkie,group 4 Lambretta engine,UK

[Frits Overmars]

question for anybody who has an opinionThat's a dangerous way of asking, Chalkie; you'll risk getting all kind of stupid answers, including mine.
if your cylinder only has a single exhaust port,how soon would you make the transition from the oblong shape to the round header diameter?I would take my time. And if the header is curved, as normally found on a bike with a forward-facing exhaust, it will even flow better if you keep the flattened profile all the way through the bend.


would the aprillia flange missmatch workFunny question, that. I never considered Aprilia a dating agency :violin: :hug:


finally,is there an optimum angle for the exhaust port as it exits the cylinder ?The optimum roof angle is about 25°; the duct floor should be shaped so that the duct volume is minimal.

[husaberg]

no particular order and so forth click on the arrow after the posters name and it will lead you to the original post for the additional information.

That depends on the port width. A single port will not be as wide as the total width of a bridged port, so the effect will be less pronounced, but the principle remains the same: each particle of exhaust gas wants to leave the building ASAP and the shortest path is radially outward. Therefore the radial lines from the center of the cylinder bore to the edges of the exhaust port describe the initial shape of the exhaust duct's side flanks.
But the duct volume should be no larger than absolutely necessary, so continuing those radial lines would be counter-productive. As the exhaust duct floor drops, these side flanks can be curved towards each other, keeping the flow cross-area of the duct constant. The picture shows the underside of the duct.


The exhaust port isn't canted downward 30°. The flange mounting face is canted downward 30° but the roof of the exhaust duct exits the cylinder at 25°.
The reason is that this angle gives the best flow.

The power valve starts opening at 10,000 rpm and it is fully open at 12,000 rpm. It can keep up with acceleration in any gear. And when you blip the throttle in neutral, the power valve servomotor moves almost as quickly as the revcounter needle.


As a side point to what Frits was saying re 25* down angle giving the best flow.This also reduces the duct area by the cosine of the exit angle,thus reducing the duct
volume.
And this then also allows steps and transitions in the flange to promote the flow exiting the Aux Ex ports,helping blowdown efficiency.
The main handbrake at the limits of power production.
The flow exiting into the duct, just as the piston cracks open the port,is dropping over a cliff - the piston face.
This is why the down angle helps flow,it is " pointing " the exiting gases toward the duct centre,not keeping it attached, normal to the piston dome.


So the reduction in cross sectional area at the bottom of the RSA exhaust port works like an integrated oval to round transition?

Do you remember the percentage of the reduction in cross sectional area, Frits?

270001



The trend has been for a long time to reduce the volume of all the ducts in modern engines.
Aprilias Ex duct had the bottom filled in such that it was higher than BDC and the corners filled to reduce short circuiting from the A ports.
And the cylinder duct vol was CNC machined to be smaller and smaller in total vol,but in the process heavily promoting flow from the Aux ports to increase effective blowdown flow.
One of the transfer duct entrys was smaller than the port area ( the B and biggest port ) and for sure the ratio between the A and B port duct entry areas was tested
to death within the limitation of the case available area between the studs, by several of the 100 R&D festerers.
The idea here is to reduce the inertia of the initial volume available to the cylinder,that has to be accelerated out of the duct by the negative pressure ratio across the port.
That Cagiva cylinder is very "old" technology.


Yea but Lozza was it a R3,5 and was the port at 70 + % and did it pull 14500,or even closer to the moon.

The curved convex shape of the Aprilia duct corresponds directly with the area increasing due to the Aux ducts entering the main.
Again the idea is to keep the duct volume down.

The 75% area at the cylinder exit is just something I discovered after running hundreds of sims, most of them worked best with an oval to round transition in the flange that started with this area
and the pipe header diameter equalled the total effective area of the ports.
Its been tested and proven so many times now, by so many other people, that it should be the first mod to make to any T or tripple port engine.
Here is a pic of one I have just done, that happened to have a tapered spigot - enabling the Aux ducts to be run all the way down into the pipe.
Check the big rad on the transfer duct/bore edge.

Simple answer re the odd shape and reduced area of the Ex duct exit is that with a 3 port cylinder, the area of the main port is plenty big enough to support the gas flow
created by the power being made.
The big Aux additional area allows better Blowdown STA, but this area is only needed above TRO.
Thus having a huge duct simply drops the velocity, reducing the wave amplitude into the header.
The Aprilia shape promotes the flow from the Aux ports by keeping the extra horizontal area all the way into the pipe - thus helping blowdown flow and overev power..
Reducing the duct vol by having area reducing steps, keeps the velocity high and again promotes the flow regime in the side ports.
There may be a case to say that the steps reduce backflow from the pipe at low rpm when it is too short,but for sure there is no outflow disruption,and in any case tests showed that power went up as the duct became smaller.
I have exhaustively ( pun ) tested the vol/shape effects on a T port ( as has Mr H ) and an oval to round transition with no steps works better.
A factory A Kit has a very small 41 by 32 oval, with a CNC transition into a 41 header.


Here is an oval to round spigot for Robs GP100 with RGV cylinder.
36mm pipe ID, oval shape at the duct exit is 36 wide by 27 high = effective area of a 31mm round..
This nozzle effect doesnt work on single port engines - I have tried.

Re stinger nozzles - if running a 18mm nozzle on a 100cc then you could connect a 20mm stinger tube to it in basically any length and this would not affect the power at all - in fact using the nozzle with a tapered section out to the bigger tube makes more power.
Aprilia/Derby twins do this as the top pipe has a stinger 60mm long, the bottom one is closer to 220, but the effect works on any 2T.

Some more RSA125 development info from Jan Thiel

"No pressure transducers were ever used in our engine development.
And time/aerea was never calculated.
The port timings remained practically the same during 15 years!
What we did was trying different angles and radiuses, mainly on
the transfer ducts. I think we tried 40 different types of transfer ducts
that did not chanche the time/aerea. It was all about in which direction
the charge entered the cilinder and how the tranfer streams influenced upon
each other! Also about 200 different exhaust pipes were tried. After 2004
nothing much was changed but we improved with different power jet and
ignition mapping. It seemed nearly impossible to improve the transfer ducts
any more. The exhaust ducts were CNC machined, using different programs,
mainly to reduce exhaust duct volume. Also about 100 head designs were tried"

Didnt calculate time area? Im guessing that means the time area requirement hasnt changed any in the last 15+ years.
So there you go its all about the transfer ducts, now where have I heard that before?
Check out the attached photos, I guess the idea of thinning the transfer duct bridge has gone out the window, and the exhaust duct hows that for a crazy shape


231454
231455
231456

As an addition to what Wobbly said about the exhaust duct-flange diameter, there is this quote from pitlane.biz:



and the photos of RSA's duct/flange

251236
251237

These changes in section at the exhaust, I have been trying to understand why they work. I lost 1 bhp on one of my old engines, after I had modified a port and a step in the exhaust, yes typical idiot, but no time no money so go for it! Unfortunately the engine granaded itself in the next meeting so could not go back to check out the changes. The port mod I have since repeated on another engine, and I'm reasoably certain it was not that. The exhaust port was round with just a step at the manifold. In checking out potential reasons I have noticed in a HRC tuning manual for the RS125 that you can remove the top mismatch on the port to manifold joint but not the lower one. So it suggests that oval is not mandatory but a step is.

Not certain if I have been sniffing too much Avgas/Castrol R, but I was wondering if the step sets up a sonic shock wave across the port, so engine side is sub sonic, and waves still go up and down pipe at supersonic speed. Therefore the width of the step and its proximity to the open port is critical, just like a jet engine intake. The advantage being possibly that it stops the shock wave going into the cylinder, from my understanding if a shock wave goes into a cavity it cause chaos to any flows (jan's comment keeping exhaust and inlet seperate). Has anyone any thoughts about this or am I off my head?
Nothing to do with ducts

http://www.youtube.com/watch?feature=player_detailpage&v=S-4Qv4B2HZI#t=276s


http://www.youtube.com/watch?v=uO2sy0cKOq0&feature=player_detailpage

[TZ350]

I was sent these pictures of another sweet little F5 bike that is coming together, its made for F5, Mini Motard and Flat Tracking and looks like a very good value for money little racer that's been well engineered, I like it.

[TZ350]

After the first North Island round I thought I had better take a look at the Beasts piston top and cylinder as Cotswold had reported a knocking from the engine.

274140

Piston crown and bore look Ok.

274139

Transfer side, the clean outer edge corresponds to the squish band in the head. I have no idea what the other flow patterns on top of the piston mean but they look nice and even.

274142

Head looks Ok, no over heating or signs of the piston touching the head even though the squish clearance is 0.6mm

274143

You have to look deep down in the plug to where the ceramic meets the steel shell to be able to tell anything about the mixture, it looks OK.

274141

This was the cause of the knocking a broken front engine mount. The small side mounts have broken off and the screw driver points to where the main spar is nearly broken right through.

[cotswold]

274141[/ATTACH]

This was the cause of the knocking a broken front engine mount. The small side mounts have broken off and the screw driver points to where the main spar is nearly broken right through.


If you need a spare down tube I cut one off one of my donor bikes

[chalkie]

thanks Frits & Husaberg for your prompt replies,was able to cut the exhaust duct this afternoon!
just need to make a new improved stub now,will let you know if it makes more power.
cheers chalkie

[jasonu]

I was sent these pictures of another sweet little F5 bike that is coming together, its made for F5, Mini Motard and Flat Tracking and looks like a very good value for money little racer that's been well engineered, I like it.

Not that it bothers me but are XR's bucket legal?

[TZ350]

Not that it bothers me but are XR's bucket legal?

This was done to death on some other thread but I can't remember what the outcome was.

And it is not one of our bikes so I don't know what all the technical details are, but it could be a perfectly legal XL, SL, CB100 engine/parts in an XR frame, hopefully the owner will fill us in.

[jasonu]

This was done to death on some other thread but I can't remember what the outcome was.

And it is not one of our bikes so I don't know what all the technical details are, but it could be a perfectly legal XL, SL, CB100 engine/parts in an XR frame, hopefully the owner will fill us in.

Fair enough mate. I hope it all goes well, F5 needs all the help it can get.
BTW any idea how No Mates' bucket went at HD last weekend?

[TZ350]

any idea how No Mates' bucket went at HD last weekend?

I don't think he ran, not enough entrys, so the mixed class got canned.

[richban]

Fair enough mate. I hope it all goes well, F5 needs all the help it can get.
BTW any idea how No Mates' bucket went at HD last weekend?

Mylaps tells some of the story. Qualified 18th and a DNF. So not so good. I would have expected that bike to smoke the 250 clunkers.

[husaberg]

Not that it bothers me but are XR's bucket legal?


This was done to death on some other thread but I can't remember what the outcome was.

And it is not one of our bikes so I don't know what all the technical details are, but it could be a perfectly legal XL, SL, CB100 engine/parts in an XR frame, hopefully the owner will fill us in.

Well the MNZ classifies the XR80 and XR100 as a trail bike. So its pretty cut and dry
So anyone who wants to argue that,they can take it up directly with them.............

Ps Rob tell the guy who's building it that i am pretty sure the MB50 transmission will go in without too much fuss.....

[TZ350]

274210274211

I am interested in knowing why there is a hot area on the edge of the squish band over the exhaust port. The squish opens up at 3 deg, is this to much?

274212274213

The piston looks like it has got hotter (same oil and ratio) but the heat mark is not so pronounced on the original copper head and that didn't have any taper in the squish area.

274209

And why is there a shadow (clean area) on the piston next to cylinder wall area between the ports? I would have expected the area in front of the transfer ports to be washed clean from the fresh mixture, not between the ports.

[F5 Dave]

. . .
And why is there a shadow (clean area) on the piston next to cylinder wall area between the ports? I would have expected the area in front of the transfer ports to be washed clean from the fresh mixture, not between the ports.
Because that Naughty pressure hasn't blown down enough pressure so that the symetrical transfer ports flow in one direction. First the hot gasses try to escape out the exhaust & then when more area is presented out the transfers. For a little while at least.

[F5 Dave]

.............

Ps Rob tell the guy who's building it that i am pretty sure the MB50 transmission will go in without too much fuss.....Don't waste an MB50 g/box on a diesel:nono:

[husaberg]

The piston looks like it has got hotter (same oil and ratio) but the heat mark is not so pronounced on the original copper head and that didn't have any taper in the squish area.

274209

And why is there a shadow (clean area) on the piston next to cylinder wall area between the ports? I would have expected the area in front of the transfer ports to be washed clean from the fresh mixture, not between the ports.
I thought you used cast Pro X That piston looks esp Wiseco like with the numbering?

Don't waste an MB50 g/box on a diesel:nono:

Oh Dave.... surprised it would worry you, Afterall its only Honda stuff and everyone knows you wouldn't get into bed with the devil would you.

[TZ350]

I thought you used cast Pro X That piston looks esp Wiseco like with the numbering?

We favor Wiseco pistons, the ProX ones we have tried gave problems, one new one even started to crack up after less than 20min on the dyno.

[TZ350]

Because that Naughty pressure hasn't blown down enough

274214

No no, its you who is being naughty. Take another look at the small area next to the bridge between the exhaust and transfer. There is that same clear patch wherever there is some cylinder wall between ports, maybe its just that the piston runs cooler there???

[jasonu]

Don't waste an MB50 g/box on a diesel:nono:

They are not much good for anything else.

[F5 Dave]

Some people like to run them in MB100s. I'd run an MB100 before a 4 banger any day (with the manufacturer name ground off the side of course).

[husaberg]

Some people do ride HONDA MB100 i guess.
I can't remember anyone posting this on the thread before.....

http://www.youtube.com/watch?feature=player_detailpage&v=R83JOHWHulw

[Frits Overmars]

274214
Take another look at the small area next to the bridge between the exhaust and transfer. There is that same clear patch wherever there is some cylinder wall between ports, maybe its just that the piston runs cooler there???Maybe, even probably. But not certainly. Clear patches on pistons can also be an indication of hot spots. Yeah, those simple two-strokes.....

[cookie1965]

I thought I'd ask the smart people here a question if I may. I've been planning to build a dyno and have been working on design and finding materials. Yesterday I happened across this:

http://i48.photobucket.com/albums/f224/cookie1965/dyno-1.jpg

It's an old Heenan Froude water brake. Funny, it's been sitting in my machinists shop the whole time we were talking inertia dyno design ideas and he never mentioned it until yesterday when we were at another shop having one of his race car motors dyno'd lol.

I was wondering if, say money were no object LOL, would I be better off converting this with a modern load cell, sensors and software or should I stick to my original plan of an inertia dyno. Or maybe there's a third option I haven't thought of?
TIA

[Frits Overmars]

My first brake (we're talking 1978) was a Heenan & Froude, same as yours, only a larger version.
The main problem was that its torque absorbtion curve was less steep than the torque curve of a racing two-stroke. So either the engine rpm would be stuck at a point somewhere in the torque dip, or it would shoot right past max. torque rpm, past max. power rpm and even past max. mechanical safe rpm.
A partial solution was to triple the water pressure in the whole system, but stabilizing engine rpm via the brake's handwheel remained a hell of a job.
My advice: stick to your original plan of an inertia dyno.

[wobbly]

Dead right Frits.
All the water brake dynos I have seen that worked well with high output 2Ts needed additional inertia,to enable the operator,or the software
to adjust the valving quick enough to get anything like a consistent load .
Even the best well adjusted PID loop control goes bananas trying to hang onto the rate of change a good 2T produces.

[cookie1965]

Thanks for the input, I've found a manual for it online and now that I better understand how it works I see that automating the sluice gates, as I first thought I'd do, would be near impossible. Oh well, I own it now LOL. Considering I paid 1/10th what one is for sale for now on e-bay maybe it's OK. It sure is cool to look at anyways.

[husaberg]

Thanks for the input, I've found a manual for it online and now that I better understand how it works I see that automating the sluice gates, as I first thought I'd do, would be near impossible. Oh well, I own it now LOL. Considering I paid 1/10th what one is for sale for now on e-bay maybe it's OK. It sure is cool to look at anyways.

I have an article somewhere i will post it tonight about converting a water dyno to computer controled somewhere it is out of FB (so unfortunatly it is a bit long winded and full of bad jokes etc.) i guess you should cope?

[F5 Dave]

. . . . if, say money were no object LOL,. . .

Sounds like you have the potential to make up to 9/10s in profit that could be ploughed into a better idea. Result.

[cookie1965]

I have an article somewhere i will post it tonight about converting a water dyno to computer controled somewhere it is out of FB (so unfortunatly it is a bit long winded and full of bad jokes etc.) i guess you should cope?

Yeah I'd love to see that. Long winded and bad jokes? Right up my alley.

[cookie1965]

Sounds like you have the potential to make up to 9/10s in profit that could be ploughed into a better idea. Result.

Maybe :msn-wink:. Lets see if that one sells first

http://www.ebay.com/itm/HEENAN-FROUDE-HYDRAULIC-DYNAMOMETER-/271101287554

[chrisc]

At the risk of opening a can of worms (people hating on the dominance of 4 strokes and the culling of 2 strokes), I am interested to know more about how modern 2 strokes have been developed for better pollution emissions. I was going to start a new thread but thought this is likely to be the place to ask, sorry if it's clogging the thread.

Any suggestions on interesting reads? I've read a small amount on direct fuel injection and such but does anyone have thoughts or interesting things of note around this?

[NOID]

[QUOTE=chrisc;1130444357]At the risk of opening a can of worms (people hating on the dominance of 4 strokes and the culling of 2 strokes)

i think that 4T was/ still is a good way to go, meny dont all have time / knowlege of building / fixing 2T engines etc they can get ok power and be really compedative for a small fee and (relability is amazing on some 4T engines )

there is the exception with people modifying 4T for $$$$$$$$$ and then blowing them up = more $$$

But theres still the 2T out there, maybe not in the high numbers like there was 10yrs ago etc but the tide will change/ new fad will come around ( FXR FAD MUST DIE SOON !!!!!!)

Iv jumped ship, was 4T for life . . . . . but pick up 2T this weekend and looking forward to getting easy power and learning more :eek:

[husaberg]

At the risk of opening a can of worms (people hating on the dominance of 4 strokes and the culling of 2 strokes), I am interested to know more about how modern 2 strokes have been developed for better pollution emissions. I was going to start a new thread but thought this is likely to be the place to ask, sorry if it's clogging the thread.

Any suggestions on interesting reads? I've read a small amount on direct fuel injection and such but does anyone have thoughts or interesting things of note around this?

Eventrude..............

[jasonu]

Maybe :msn-wink:. Lets see if that one sells first

http://www.ebay.com/itm/HEENAN-FROUDE-HYDRAULIC-DYNAMOMETER-/271101287554

That's in my neck of the woods (in summertime anyway)

[wobbly]

The issue the industry is up against now is that the technology to make a 2T BETTER than a 4T in EVERY way is licensed and patented.
Evninrude and Bombadier use direct injection systems that create stratified charge distribution.
This gives an engine thats, lighter, more powerful,less emissions, more fuel efficient and WAY cheaper to service.
But this technology costs a fortune to implement.
All it needs is a quantum jump for someone to come up with a new way of doing this, sell it to the Asians, make a trillion 50cc
scooters using it and 4Ts will quickly disappear back up Hirochios bum, from whence they came.
Might even see 500GP with bikes that do 50mpg.

[twotempi]

There was a post regarding bead-blasting for cleaning plugs which got tacit approval.

Is there a product that will clean chemically them - Tergosol, oven cleaner, BBQ cleaner ?? - that will do the same job ??

Conc sulphuric/nitric acid just produces fumes !!

( that was a joke by the way )

[twotempi]

Carbon Tet is a no-no as it leaves traces on carbon which shorts out the plugs. If you can still buy the stuff.

[TZ350]

Oven cleaner, BBQ cleaner ??


Carbon Tet is a no-no as it leaves traces of carbon which shorts out the plugs.

BBQ and Oven Cleaner to get rid of oily deposits, dry then bead blast is my pick, we use Breakcleaner in an aerosol can when we need to clean a plug up at the track.

Carbon Tet is rapidly absorbed through the skin and lungs and is hard on the kidneys and Liver and is a carcinogenic.

[jasonu]

BBQ and Oven Cleaner to get rid of oily deposits, dry then bead blast is my pick, we use Breakcleaner in an aerosol can when we need to clean a plug up at the track.

Carbon Tet is rapidly absorbed through the skin and lungs and is hard on the kidneys and Liver and is a carcinogenic.

Why don't you simply buy new plugs and be sure to have a couple on hand at the track?

[twotempi]

"Carbon Tet is rapidly absorbed through the skin and lungs and is hard on the kidneys and Liver and is a carcinogenic." - which is why you can't buy it anymore.

Interesting that Methanol has same physiological properties as carbon tetraclhoride but the classic guys still use it for fuel without any health precautions whatsoever.

Also if you are following a "Methanol" bike you certainly know it by the exhaust fumes - they stink !!

Is "Brake" cleaner and carb cleaner the same stuff ?? The can has different label but ............................

[twotempi]

"Why don't you simply buy new plugs and be sure to have a couple on hand at the track?"

At $25 a shot the bottom of the toolbox becomes a very valuable item. How many plugs land up rattling around in the bottom of toolboxes ??

Seriously though, if there is a way of "refreshing" them effectively why not do it . The Green Party will be proud of us - Recycle, Repair & Race


Forgot to mention - I run twin-cylinder stuff so the issue is X 2 !!

[jasonu]

"Why don't you simply buy new plugs and be sure to have a couple on hand at the track?"

At $25 a shot the bottom of the toolbox becomes a very valuable item. How many plugs land up rattling around in the bottom of toolboxes ??

Seriously though, if there is a way of "refreshing" them effectively why not do it . The Green Party will be proud of us - Recycle, Repair & Race


Forgot to mention - I run twin-cylinder stuff so the issue is X 2 !!

Are bucket racers really using $25 spark plugs?
If yes, I doubt they would end up rattleing about at the bottom of the tool box.

[husaberg]

Sounds like you have the potential to make up to 9/10s in profit that could be ploughed into a better idea. Result.


Yeah I'd love to see that. Long winded and bad jokes? Right up my alley.

Unfortunately the article is not the one i thought
While I can envisage a way to alter the sluice gates controlled by a pressure control unit from a water pump (rob will know what i mean) but as Frits and Wob and the article (when i get around to posting it) say the steady state hp reading from a Watergate Dyno (although extremely accurate for its purpose) unfortunately doesn't correspond to anything a race engine is going to be asked to do on the track.

i think Dave is onto something there.........

[cookie1965]

While I can envisage a way to alter the sluice gates controlled by a pressure control unit from a water pump (rob will know what i mean) but as Frits and Wob and the article (when i get around to posting it) say the steady state hp reading from a Watergate Dyno (although extremely accurate for its purpose) unfortunately doesn't correspond to anything a race engine is going to be asked to do on the track.

i think Dave is onto something there.........

That's what I was thinking, at simplest either a variable speed pump or a servo control/worm gear on the sluice gate handle. The variable speed pump would be much simpler (since I have a shop full of pumps). But I wasn't sure if the sluice gates did more than control the flow, maybe they control the angle of the water entering the rotor? I'm going to pursue this a bit since I own the thing, figure out if I can make it work.

[Haufen]

Now you can express the radial characteristics of the transfer ports with positional and directional angles, regardless of bore and stroke.
And you can express the ports' axial characteristics with axial angles, but that only holds for engines with identical bore/stroke-ratios, as Wobbly explained.
Your approach of using a height h1 in the cylinder where the transfer port's roof would hit the opposite cylinder wall, is very good, but you need to express h1 as a percentage of the stroke. Then you will have a truly universal value. Then you will also see that short-stroke engines require smaller axial angles.

Your posts are always worth fiddling with the search function, Frits!

I've got a question regarding your post on scavenging angles with different bore/stroke ratios quoted above. Concerning the axial angles, what would you propose to do with them if the transfer port height (in percent of the stroke) is going to be reduced?


Would you propose to keep the position where they would intersect with the middle of the bore thus increasing the angle?
Or would you propose keeping the angle constant and thus reducing the scaled h1 by the same amount (in mm) as the transfers are going to be reduced?

[Frits Overmars]

I've got a question regarding your post on scavenging angles with different bore/stroke ratios quoted above. Concerning the axial angles, what would you propose to do with them if the transfer port height (in percent of the stroke) is going to be reduced?

Would you propose to keep the position where they would intersect with the middle of the bore thus increasing the angle?
Or would you propose keeping the angle constant and thus reducing the scaled h1 by the same amount (in mm) as the transfers are going to be reduced?

If you reduce transfer port height and thus transfer timing, there will be less time available to scavenge the cylinder at a given rpm. To compensate, you would need more vertical velocity in the scavenging colum which can be achieved by steepening the scavenging angles.
But less transfer timing will also mean less transfer time.area; this will lower the rpm of maximum cylinder filling, and the time available for scavenging will increase because of this lower rpm. All in all I think you should not steepen the scavenging angles.

[husaberg]

That's what I was thinking, at simplest either a variable speed pump or a servo control/worm gear on the sluice gate handle. The variable speed pump would be much simpler (since I have a shop full of pumps). But I wasn't sure if the sluice gates did more than control the flow, maybe they control the angle of the water entering the rotor? I'm going to pursue this a bit since I own the thing, figure out if I can make it work.

From what i understand (although i think there is a bit about a similar dyno on the elsberg tunning site) (http://www.elsberg-tuning.dk/the%20bikes.html)
<img src="http://www.elsberg-tuning.dk/images/dynoshaft.jpg" width="350px"/><img src="http://www.elsberg-tuning.dk/images/dynodec11.jpg" width="350px"/><img src="http://www.elsberg-tuning.dk/images/hfdpx0.jpg" height="260px"/>
Is the resistance for this dyno is controlled by the level of water.
No doubt there would be more sophisticated ones out there.
I definitely have seen something where someone converted a hydraulic dyno read out to work with a computer display rather than a manual strain gauge but where???
oh below the text version of the dyno article off the authors site, some different stuff there like injection etc. (http://www.iancramp.co.uk/journalism.html)

[cookie1965]

From what i understand (although i think there is a bit about a similar dyno on the elsberg tunning site) (http://www.elsberg-tuning.dk/the%20bikes.html)
<img src="http://www.elsberg-tuning.dk/images/dynoshaft.jpg" width="350px"/><img src="http://www.elsberg-tuning.dk/images/dynodec11.jpg" width="350px"/><img src="http://www.elsberg-tuning.dk/images/hfdpx0.jpg" height="260px"/>
Is the resistance for this dyno is controlled by the level of water.
No doubt there would be more sophisticated ones out there.
I definitely have seen something where someone converted a hydraulic dyno read out to work with a computer display rather than a manual strain gauge but where???
oh below the text version of the dyno article off the authors site, some different stuff there like injection etc. (http://www.iancramp.co.uk/journalism.html)

Converting to computer display is the easy part. Replace the spring/weight affair with a modern strain gauge and voila. I can buy a kit with everything needed. The hard part is automating the load controls so it can work right, as Frits and wobbly said. They're right about the fact that an inertia dyno would produce better data obviously too. It's been an interesting exercise and I've educated myself a whole bunch about dynos but I think I need to return to my original plan.

[husaberg]

For inspiration for Rob i have posted pics of the Porcupine AJS head before here is another variation plus a late Aircooled cylinder and head.
<img src="http://nachtflug.smugmug.com/photos/178698900-L.jpg" width="340px"/><img src="http://www.mxbikes.com/forum/getfile.php?key=1215983384&att_id=1951&site=mxbikes&bn=mxbikes_maico" width="340px"/><img src="http://www.eastcoastmaico.com/wprs/wp-content/uploads/rv01_JPG.jpg"width="340px"/><img src="http://t1.gstatic.com/images?q=tbn:ANd9GcSGMaYLpG4jvlrUML3zFGd1ADfAK2l8T oAcJGZNOeTp_d1xs7HN_k5ddt0" width="340px"/><img src="http://www.maico.mxbikes.com/atkengine.jpg" width="340px"/>

Note the spigoted head and the offset squish

[jasonu]

For inspiration for Rob i have posted pics of the Porcupine AJS head before here is another variation plus a late Aircooled cylinder and head.

Looks familar

[TZ350]

For inspiration for Rob.

Thanks Husa for the head ideas and here is a bit of Bucket Racing at the Island, now those guys are realy good.

<iframe src="http://www.youtube.com/embed/Ph0SjLC_lqk" allowfullscreen="" frameborder="0" height="315" width="560"></iframe>

[husaberg]

I see your island and raise you some additional Irish road racing bits as well.
Fooken mad they are aye Man.......

http://www.youtube.com/watch?feature=player_embedded&v=vj6aFeHwShQ

[chalkie]

have any of you guys any idea's on what sealant/grease would be good for heat transfer between a head insert & the head itself ?
I'm machining manually to the best of my ability but was worried about any small voids between the two.
thought probably copperslip might be ok,but guess that loctite or RS components might do something perfect.
any idea's appreciated !
cheers chalkie

[TZ350]

have any of you guys any idea's on what sealant/grease would be good for heat transfer between a head insert & the head itself ? RS components might do something perfect.

Heat Sink compund/paste sold for Computer CPU's would be my pick. The things to look for is the amount of silver in it (the more the bettor) and if it drys out.

Trademe

http://www.trademe.co.nz/computers/components/cooling-fans/thermal-compounds/auction-539878263.htm

(http://www.trademe.co.nz/computers/components/cooling-fans/thermal-compounds/auction-539878263.htm)http://www.trademe.co.nz/computers/components/cooling-fans/thermal-compounds/auction-540371206.htm

[Grumph]

There's also a very similar paste which is used for bedding heating elements in press dies.
I last used it years ago - if it isn't the same stuff already posted, it'll be a higher temp version.

[wobbly]

Now thats what we are talking about

https://www.youtube.com/watch?v=fY6ZHiEWWhw

[wax]

That looks viscious . when its setup right its going to be awesome.

Whe ended up wining the 24 hour open class scooter race on the weekend. Scooter sat at 13500 rpm or close to it for 24 hours. I will pull it down in a few weeks and see what it looks like inside

[kel]

So this picture of the Aprilia 250 inlet and disc has intrigued me for some time

274419

it was suggested the acute angled edge (if thats the correct way to describe it?) was the closing edge, thus giving a soft closing effect. I couldn’t make sense of this, yet it didn’t seem logical for it to be the leading/opening edge either as this would surely just give away time area.
So it came up recently on pit-lane.biz “All that you wanted to know on Aprilia RSA 125 ...“ thread. The following summarises a very interesting discussion


Manuel Rainer = i am driving a 125 ccm TM KV 95 rotary valve kart engine with 86°-160° timing made like this:

274420

and i also testet one like this:

274421

but it doesnt works reali well.

MIC = This is because there's a big difference between your KV95 engine and the RSA. On the KV engine the inletport is above the rotary valve's centerline while on the RSA it's on the right side. The best flow with partial open carburator is by opening the inlet port from the bottom up. This is easily done on the RSA by having a disc as seen on picture. On the KV you need something like the "grinding" picture to get a similar result.

Howard Gifford = Our engine has a design drawback in that one inlet port opens from the bottom and one opens from the top. The one that opens from the top has less airflow and I suspect less power than the one that opens from the bottom.

Jan Thiel = I thought about this when we designed the RSA. And made the inlet open from the bottom!

So there you have it from Mr Thiel himself, the inlet port should open from the bottom up. The angling of the disc as per the first picture is implemented in this way to best simulate the effect of opening from the bottom up!
edit; the third photo is of the FPE's RSA inlet.

[kel]

Frits, I have a question on the above post re disc valves if I may. The angled opening edge of the valve will sacrifce time area, in my engine this is a problem as the time area is borderline for the power Im wanting out. To recover the time area should I start experimenting with opening the inlet earlier? (keeping in mind the tight nature of the kart tracks our machines are used on). Current timing is 140/80 which while not radical is nearing the limits for kart track use, or is it?

[husaberg]

<img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=252117&d=1323157880" height="540px"/><img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=274475&d=1355123116" height="540px"/>



As I mentioned above the disk is a limiting factor, the diameter is 106 mm.

Measuring inside a spare GP125 cover the disk looks to be 115mm diameter.

Somebody asked about the Aprilia's inlet disk diameter. From memory I would say it was 126 mm.

Its definitely a 125 Gav.
end goal is a kart track useable rwp 24hp (50% more power than my FXR).


Frits, I have a question on the above post re disc valves if I may. The angled opening edge of the valve will sacrifce time area, in my engine this is a problem as the time area is borderline for the power Im wanting out. To recover the time area should I start experimenting with opening the inlet earlier? (keeping in mind the tight nature of the kart tracks our machines are used on). Current timing is 140/80 which while not radical is nearing the limits for kart track use, or is it?

[wobbly]

One of the fastest open class kart engines in the country is a Pavesi 144 I built a while ago.
Its RV timing is 140/88 with a 39mm carb on pump gas.
Open any earlier and the jetting becomes impossibly finicky to get right, close any later and it loses all the mid power, due to no PV.
But close any earlier and it wont rev to 13800.
As always a compromise has to be struck.
The RV is 126 dia thus port time area isnt the issue, its the shape of the powerband needed to be fast that has to be right.

[Frits Overmars]

Frits, I have a question on the above post re disc valves if I may. The angled opening edge of the valve will sacrifce time area, in my engine this is a problem as the time area is borderline for the power Im wanting out. To recover the time area should I start experimenting with opening the inlet earlier? (keeping in mind the tight nature of the kart tracks our machines are used on). Current timing is 140/80 which while not radical is nearing the limits for kart track use, or is it?Wobbly said it all. Closing the disc later than 88° aTDC costs top end power; closing it earlier would give more bottom and mid power, but with a 39 mm carb the engine would run out of breath too soon. Aprilia used 42 or 43 mm carbs (most riders preferred the 42) and a closure timing of about 85° aTDC.
What you can do with any carb, large or small, is to shorten the inlet tract as much as possible. This may allow you to close the disc earlier, giving a more civilized engine behaviour, and still maintain decent crankcase filling at high revs.
Or you could go the opposite route: increase crankcase volume, increase inlet tract length, and leave the inlet disc out altogether: 24/7-inlet. But then you will need some sort of hinged reed to enable starting. And I don't think anybody will manage to get decent carburation in both the reed-phase and the 24/7-phase; It will take fuel injection to get both phases right.

Opening the disc earlier in order to increase inlet angle.area will function mathematically but angle.area is only one of the factors affecting intake flow. It would not be very wise to open the disc when crankcase pressure is still higher than the pressure upstream of the disc.
The lower the revs, the more time there is available for the crankcase pressure to drop; at 9000 rpm you could open the disc before BDC to good effect; crankcase pressure would not drop so far and scavenging flow would not be slowed down so much, resulting in more mixture reaching the cylinder. But such an early opening timing would seek revenge at higher revs.
Another effect, also mentioned by Wobbly: the earlier you open the disc, the smaller the pressure difference between crankcase and inlet tract and the weaker the suction pulse at the needle jet, which makes setting the carburation increasingly difficult.

[kel]

Thanks guys. I will cut the disc to the same base timing as per the regular disc, test and compare, then add a couple of degrees to the closing point and test again. Probably should move the entire inlet to the rotor side of the crankshaft as this would give the shortest possible inlet plus I wouldn't have to remove the clutch etc to change disc.
Maybe an emot conversion kit is called for http://www.emot.nl/webwinkel/index.php?act=viewProd&productId=148

[F5 Dave]

So your new Avitar; Are you practising levitation, or just giving the beast a good kicking while its down?:shutup:

[husaberg]

Thanks guys. I will cut the disc to the same base timing as per the regular disc, test and compare, then add a couple of degrees to the closing point and test again. Probably should move the entire inlet to the rotor side of the crankshaft as this would give the shortest possible inlet plus I wouldn't have to remove the clutch etc to change disc.
Maybe an emot conversion kit is called for http://www.emot.nl/webwinkel/index.php?act=viewProd&productId=148

This fellow also does one as well.
http://www.vrm.se/
Click on the UK (flag unless of course you can read Swedish)then click on the picture of the reed valve .

[kel]

or just giving the beast a good kicking while its down?
Hey the Beast is my friend. Sure its a little wild and needs breaking ... seems the feeling was mutual :bleh:

[cotswold]

Hey the Beast is my friend. Sure its a little wild and needs breaking ... seems the feeling was mutual :bleh:

It does that to everybody, beasts aren't friendly.

[Kickaha]

Anyone for a new Konny engine?
http://www.steveenglish.com/forum/download/file.php?id=7389&t=1
http://www.steveenglish.com/forum/download/file.php?id=7390&t=1

[TZ350]

We ended up wining the 24 hour open class scooter race on the weekend. Scooter sat at 13500 rpm or close to it for 24 hours. I will pull it down in a few weeks and see what it looks like inside

Sorry, I have been away for work for a while, just got back.

Congratulations on your win, any pictures? and I would love to see some pics of the engine when you get to tear it down for inspection.

[wax]

Sorry, I have been away for work for a while, just got back.

Congratulations on your win, any pictures? and I would love to see some pics of the engine when you get to tear it down for inspection.

Thanks alot. if you pm me your email I will show you some pics when I tear it down.

[TerraRoot]

start a new thread, i'd like to see too. :(

[cotswold]

I think we will stick to eventful as a description of this weekend.
Saturday was practise and we went richer on the main and leaned out the needle ( ask Rob he knows ) and the beast spent a few laps doing what it does best until it developed a phantom problem that needed a bit of attention. I took the beasts little sister out to qualify for sundays race and managed 11th even though I only got 3 laps in due to carb sticking issues (float needle valve). That was it for saturday. Sunday saw Rob spilling the beasts innards all over the grass to find out what was causing saturdays problem, I fixed the other bikes carb and took it out for morning pratice, when I got back in it was straight out on the beast to see how it was after a bit of surgery. It was like a different bike from Mount wellington and pulled out of the corners very nicely and Rob is working on fattening up the mid range so look out.

Race one
11th on the grid and the beast hurtled away and we worked our way up to 5th within a couple or 3 laps, the fast 4 were still in sight and it looked like I may have a fast but lonely race in that position until at the end of the straight just as I was tipping in for the right hander the beast nipped and threw us both down the road for a skid, no damage to bike or rider.

Race two
Out on the little sister and 11th on the grid equated to 11th in the race util I lost concentration and binned it at the hairpin, got on and finished where you would expect.

Race 3
In a solid mid pack and back concentrating (still on the little sister) I had a recurrence of the float sticking and retired.

What this weekend showed me was that the Beast with a pretty average over 50 rider on board can mix it with the fastish boys but the same rider on a bike with 20hp can't

The seizure was a bit of a story in it's own right and I'll let Rob walk you through that one

[TZ350]

Sunday saw Rob spilling the beasts innards all over the grass to find out what was causing Saturdays problem.

A big thankyou to FarmerKen for bringing a complete clutch assembly back with him Sunday morning for the Beast.

As we had initially thought that the jerky transmission problem could be smeared driving dogs or a bent selector or more likely damaged splines in the clutch hub, which has happened before. I wiped the clutch cover off to replace the clutch with FarmerKens spare but as it turned out the problem was that the gear selector was not moving far enough to select the next gear, and that was easily fixed.


Race one
11th on the grid and the beast hurtled away and we worked our way up to 5th within a couple or 3 laps, the fast 4 were still in sight until at the end of the straight just as I was tipping in for the right hander the beast nipped and threw us both down the road for a skid, no damage to bike or rider.

While I was setting the clutch up I noticed oil in the magneto housing and after the Sunday practice when we were changing sprockets I noticed how hot the Beast had been running and intended to up the main jet but in all of the rush it got forgotten.

So the nip up could be due to a leaky timing side oil seal or to, to small a main jet. I really should get a EGT and CHT gauge/data logger and use it like Wobbly suggested for keeping the jetting right and a crank case pressure tester like F5Dave has posted would be a good idea too.

Wobblys idea is that you find the optimum main jet using the dyno and then jet the bike at the track to achive the same EGT as it did on the dyno.

And another big thankyou to Cotswold for riding the thing and giving me a chance to straigten the Beasts kinks out and Henk for lending me a blow up mattress, what a life saver.

[wax]

This is the system I use its awesome. Made by josh alleman http://www.thescootergarage.com/
http://i215.photobucket.com/albums/cc79/waxracing/IMG_1902.jpg

[husaberg]

A big thankyou to FarmerKen for bringing a complete clutch assembly back with him Sunday morning for the Beast.

We initially thought that the jerky transmission problem could be smeared driving dogs or a bent selector or possibly damaged splines in the clutch hub, which has happened before. I wiped the clutch cover off to replace the clutch with FarmerKens spare but as it turned out the problem was that the gear selector was not moving far enough to select the next gear, and that was easily fixed.



While I was setting the clutch up I noticed oil in the magneto housing and after the Sunday practice when we were changing sprockets I noticed how hot it had been running and intended to up the main jet but in all of the rush it got forgotten.

So the nip up could be due to a leaky timing side oil seal or to small a main jet. I really should get a EGT and CHT gauge/data logger and use it like Wobbly suggested for keeping the jetting right and a crank case pressure tester would be a good idea too.

With the clutch you ever able to adapt a DR clutch pressure plate onto the beast Rob?
I can hear (reverberating in my head) grumbles from the old tuners that Air cooled 2 strokes are petrol cooled....
I did see a ram air cowling on TM the other day to (http://www.trademe.co.nz/motors/motorbikes/parts-for-sale/other/auction-542111881.htm):psst: They would look neat on a Suzuki

seen this today also........Much sturdier than i remember
http://www.draganfly.co.uk/shop/assets/own/4.gif

[wobbly]

Any engine with a case leak will run rich, despite all the head scratching thinking it will suck air and go lean.
A leak will compromise the pumping part of the cycle,and the bigger the leak,the less fuel/air mixture is pumped.
If you jet down seeing a rich plug, it will seize, because then insufficient fuel/oil, is being ingested.
So unless you have pressure tested the whole engine before hitting the dyno, you will not be sure you have an accurate baseline.

If you have the RAD from the dyno runs plus the egt for optimum power then its easy to set up at the track.
BUT - beware, having only the drum inertia will not load the engine sufficiently , for long enough, to simulate the jetting required for roadracing.
For this you need a heap of eddy current load control to slow the acceleration rate in the higher gears of an all gear blast.
Then you can see the egt stabilise when at full noise for long enough, in 6th gear.

Just did this on Saturday at Taupo with one of the RZ400 - F3 racebikes.
The ref egt for max power in 6th on the dyno was 1255.
The RAD at Taupo on the day was 102 so I needed to go up one jet size from what we had at the RAD 99 dyno ref.
The egt max after practice one ( with the longest straight we now run on ) was 1235/1275, so went up one more on the LH side and 2 on the RH.
This gave max recall from the next run of 1197/1204, thus I could see we had full control of the egt and a split of 2 jets.
Ran 4 by 20 minute sessions like that, and from a full noise plug chop at the end, I would now add 1* of timing to the RH side, and go back to a 1 jet split with one size leaner overall.
This then gives us a new baseline at 102 RAD.
Safe as houses, and fast as hell when you have all the info, and good plugs that read both ignition advance and jetting.

[2T Institute]

giving me a chance to straigten the Beasts kinks out and Henk for lending me a blow up doll, what a life saver.


So more than a few kinks to straighten out then :facepalm: FWIW I wouldn't have lent you mine :laugh:

[TZ350]

.... got the first A-Grade race of the day.


http://youtu.be/qFXF3Isjf_0

Near miss Crazyman! Damn dirtbikers!!!!

Cameo appearance by Cotswold and the Beast plowing up some dirt.

In practice the 30hp bikes of Cotswolds and Speedpros did not appear to have any real speed advantage over Regan's and Rich's FXRs up the back straight, but strokers with anything much less appeared to be at a real disadvantage.

Half way into the clip you can see the fast 24hp FXR's of Regans (colorful leathers) and Rich's rocket easily gapping the low low to low 20hp 2-strokes of Rick52's, Garrys and Dave M's each time they went up the back straight.

In the last race Dave M decided to sit it out and wait until he gets his 30 hp engine. He figured there was no point in hurting himself trying to make up the power deficit with extreme cornering speed and out riding his bikes abilities.

In race two Rick52 was able to take advantage of a mistake RichBan made as he braked for the hair pin and took the lead which he held to the end. Rick was riding the wheels of his bike and its the first time I have seen an RS chassis flapping the front wheel about as he changed direction coming down the hill, great effort and a well deserved win but not repeatable in race three, it needed Rich to make another mistake which he didn't.

To me it looked like the front running 2-Strokes were to under powered for the job which left to much for the riders to make up with their riding talent, it just couldn't be done.

Race 1 10 laps 4T 4T 2T 2T 2T
Race 2 15 laps 2T 4T 4T 2T 2T
Race 3 20 laps 4T 4T 2T 2T 2T

Full results including individual lap times.

274768 274769


Short set of photo's from North Island Championship Rd2. Mainly of the A Grade boys in action.


http://youtu.be/di3fdPznLlg

Race Day:
Two seconds and a third for Regs; massive starts helped close the grid gap. but Richban & Rick had the pace up front; none the less they were great races to watch. Crazyman finished mid pack on the borrowed bike; which was a sterling effort.

[kel]

In race two Rick52 was able to take advantage of a mistake by RichBan in the hair pin and took the lead which he held to the end. Rick was riding the wheels of his bike and its the first time I have seen an RS chassis flapping the front wheel about as he changed direction coming down the hill,

Thought I was seeing things when the wheel left the ground, have ESE been assisting in engine development? Straight line speed was clearly higher than the other 2 strokes.

[richban]

In the clip you can see the fast 24hp FXR's of Regans (colorful leathers) and Rich's rocket easily gapping the low low to low 20hp 2-strokes of Rick52's, Garrys and Dave M's.



Regan's bike is down a little on power to mine. Its the weight difference and the riding ability that has him looking so fast. Also when Rick came past after my cock up there was know way I was gaining anything till maybe the very end of the straight. And then there was nothing in it. I would say they are maybe 40kg lighter than me and my bike. That evens things out quite a bit. Also you have to factor in that rick looked quite rough in the morning I was feeling maybe 2% better than he looked. Regan only had 3 beers. Smart move for sure.

[TZ350]

My father came along to watch the racing on Sunday and set up a camera ... The video is awesome. Thanks Dad!! Video: http://www.youtube.com/watch?v=wDnJy6F0YRE

<iframe width="560" height="315" src="http://www.youtube.com/embed/wDnJy6F0YRE" frameborder="0" allowfullscreen></iframe>

Really great clip made by Str8's Dad ...

[crazy man]

Regan's bike is down a little on power to mine. Its the weight difference and the riding ability that has him looking so fast. Also when Rick came past after my cock up there was know way I was gaining anything till maybe the very end of the straight. And then there was nothing in it. I would say they are maybe 40kg lighter than me and my bike. That evens things out quite a bit. Also you have to factor in that rick looked quite rough in the morning I was feeling maybe 2% better than he looked. Regan only had 3 beers. Smart move for sure.your right . to this day we have never done any dyno tuning so can't wait till we have are dyno up and going to pull some more ponys out of it

[Yow Ling]

your right . to this day we have never done any dyno tuning so can't wait till we have are dyno up and going to pull some more ponys out of it

We are very very close with our dyno , so not far behind you. Have run up the drum and the drum sensor is being logged, just need to hook up the ignition sensor and set the value for the drum inertia.

274788

274787

[TZ350]

274790

Help Wax or someone else who realy knows, which way does the belt rotate? on a Yamaha Zuma, anti clock wise? and is this the same for all CVT scootor matics? Not knowing how the final drive reduction box is arranged leaves me guessing about the drive belts direction.

[speedpro]

anticlockwise. front pulley is fitted to end of the crankshaft itself so rotates at engine speed. at high ratio the rear pulley is doing engine speed times CVT ratio so it can be spinning pretty quickly.

[speedpro]

Just one place you can get cheap aftermarket parts:

http://stores.ebay.com/jiangwayne-com-Store/CYGNUS-X-Flame-X-125-NXC125-/_i.html?rt=nc&_fsub=2560797013&_sid=12311413&_trksid=p4634.c0.m14.l1581&_pgn=2

[TZ350]

Thanks for that, I wasn't sure because the engine could be run in either direction.

[TZ350]

seen this today also........Much sturdier than i remember
http://www.draganfly.co.uk/shop/assets/own/4.gif

Thanks for the Ariel crank pic.

[TZ350]

Starting from the beginning I have been trying to find the posts that talk about pipes and collate and edit them. There is heaps of it and pages 620 630 640 and 650 have un edited collections of raw material.

p352

The exhaust open point has very little to do with creating power due to "pressure" on the piston for "longer" with lower timings.
The gas pressures soon after TDC ,that creates the real power, is up over 80 bar, the pressure at Ex open is a couple of bar at best.
Moving from 200* to say 190* creates jack shit extra exertion of pressure on the piston to create torque, that then creates HP.
But the real issue is that down at 190* duration we get a huge amount of superposition of the gas pulse exiting the exhaust, on top of the residual pressure at the port.
This adding of a new pulse on top of an existing residual pressure means the wave front running down into the header has a huge relative amplitude, and this creates a huge depression at the port around BDC.
This also means we have port/pipe resonance over a much wider range and at a much high higher level than can be achieved at 200* duration.
In a conventional design we are forced into a corner by needing to create as much BlowDown STA as we can, and raising the timing is the only available route.
This pushes us away from the ideal port/pipe interaction timings, but is a compromise we are forced to accept to create the + 200psi bmep's needed, to be competitive.
Just another small detail that many overlook, or are unaware of.

p411

The header length should be in the 31 to 33% range.

p412

If I were to explain pipe design I would need to write a book,but in general things are pretty straight forward in relation to the % values.

End of header is always 31 to 33% and end of diffuser is always 62 to 68%.

To see the effect of a silly long header, you can watch the pressure ratio at the Ex port, and thus the effect this has on the depression in the cylinder.

We are looking for the lowest and widest negative ratio we can get around bdc when the transfers are fully open.

A long header delays the beginning of the depression too late in the cycle, when in the power band.

In a race 2T we are always fighting power range Vs peak power.

Shorter diffusers create steeper angles, thus greater wave amplitude, but this narrows the effective band width.

So - in general the best compromise is around 66%.

P413

The % I quoted for header means that portion of the length from piston to rear cone end.
Its from the piston to the beginning of the diffuser, what happens in between isnt relevant.
Unless of course you use a small Ex duct and a bigger header, that makes more power.
And of course same for the diffuser end, that is simply 66% of the length from the piston to the end of the rear cone.


For a race engine there are no minuses to a long rod.
Using 110 in the 50 stroke means you are on the money with the Aprilia RSA - that went OK for a 2T.
Increased weight and increased small end load don’t mean shit unless you are reving the 50 stroke to 16,000 - then all light weight parts are needed.


Picture says more than a 1000 words
(got them from kreidler.nl forum )

p420

The bulge, just outside the bore in the T port exhaust of an RS125/250 Honda type cylinder, hugely increases the flow rate during blowdown. This increase in effective flow is dramatic enough, when compared to a straight sided exit, that it must be taken account of when modelling the port in EngMod2T.


Well in saying that T ports use the bulge because of the bridge interfering with flow is the obvious answer, and I agree.
But these are bloody 2 strokes we are talking about and very little seems to work in the way you might think at first glance.
I would put the question, and it may be one hell of a discovery if it works.
Take a maxed out single Ex port like the one on TeeZees 31 Hp 125 engine - that is blowdown limited by design - though the small carb may mask the effect somewhat I would say.
Grind the bulges on the top 1/2 of the port, outside the cylinder wall, above the transfers to see if this increases blowdown flow.
Pretty easy to test with a suck thru the Ex port, before and after, on a flow bench, and a piston sitting at the transfer open point.
Then to the dyno - it will do one of five things.
Flow more and make more power,flow more and make less power,flow less and make more power, flow less and make less power - or finally - do nothing, all of which will make sense only after the tests.
Shit, I really hope it makes more power,as I love thinking outside the box - and to make a discovery that works , most dont sadly.


That depends on the port width. A single port will not be as wide as the total width of a bridged port, so the effect will be less pronounced, but the principle remains the same: each particle of exhaust gas wants to leave the building ASAP and the shortest path is radially outward. Therefore the radial lines from the centre of the cylinder bore to the edges of the exhaust port describe the initial shape of the exhaust duct's side flanks.
But the duct volume should be no larger than absolutely necessary, so continuing those radial lines would be counter-productive. As the exhaust duct floor drops, these side flanks can be curved towards each other, keeping the flow cross-area of the duct constant. The picture shows the underside of the duct.

P427

Nothing too much off the mark - except the old bullshit tale about the pipe pulling the reeds open.
How it goes is that the diffuser sucks like hell on the cylinder around BDC - this pulls gas out the transfers, they pull on the case, and this opens the reeds, allowing more mixture in.
Crap.

Here is a sim trace of a RGV100 at 13,000 making 40 odd crank Hp.
BDC is exactly between TPO and TPC, the reed lift down the bottom isnt showing the reeds much open till TPC - well after BDC, so the pipe action isnt affecting the reed lift at all, apart from
a delayed reaction due to petal stiffness and column inertia in the intake.

Re smaller case volume, I have measured one of those engines and its case com is exactly 1.3 on one side and 1.29 on the other with around 540cc from memory..
This is alot smaller than an Aprilia at 640cc.
But its case vol is relatively large in comparison to 2T technology at the time.
In a 125 project I have just finished, with a case reed, 1.3 gave the best result.
Going down to around 1.24 of the RSA spec lost around 2Hp with the reeds, no matter what I did with intake length and petal stiffness, pipe geometry or carb size.

Re the squish shape and chamber geometry.Yamaha always had odd ideas about what was correct, or best, and never really led the way at all until unleaded became mandatory.
Then the YZR was fast once Kennys boys got them on Asklands dyno.
And they kicked everyone's arses , even in 250 when they fitted the spool valved cylinders off the 500


… the pipe sucks like hell at BDC,the sim pressure ratio trace shows that dramatically when the diffuser shape is correctly designed.
Pipe depression causes a big pressure ratio across the transfer duct/cylinder boundary, and it is this effect that causes the bulk flow around BDC. But what I was alluding to, was that to then go on to say that the pipe opens the reeds, around BDC, just isnt true.

Re the carb venturi - having the smallest point within the carb up at the slide will reduce the divergent angle up to the RV area. If bad turbulence created a flow loss capability, the bench would show this immediately, on the dyno it could be several things causing less power to be produced.

Yamahas spool valve would seem to be the best system for a single or 3 port setup.
It is always close to the piston, no matter what leading edge height it has, and can also control the secondarys at the same time. Aprilias multi section blade is a good patch up of a flawed design, but it doesnt control the secondarys - maybe not such a big issue in a full noise application.

For the T port, Hondas dropping gate works very well.Its design in the RS250 cylinder is much better than the ones Husaberg showed in that the pivot point is alot further
away from the piston.Thus the arc away from the piston is alot slower.
Suzukis twin multi section tubular valves are complex but clever as well, and like Hondas gate they conform well to the port roof when open.

P428

In order to take full benefit of a large crankcase volume you need free-flowing transfer ducts. That means: large cross sections, short gas column lengths and large time.areas. Of course I don't know which dimensions you entered into the sim, but am I wrong in thinking they may have been more restrictive than the Aprilia values?

Skinny exhaust pipes, high crankcase compression and narrow transfers with timings over 140° were common in the sixties. These factors were interdependent: the skinny pipes hardly produced any decent exhaust suction, so you needed the pumping action of the small crankcase volume. And because of the narrow transfer windows you needed long timings to get anywhere near workable time.areas.

The energy of a moving gas or mixture column depends on its mass and its velocity. In ducts with large cross sections the flow velocity does not rise too high because the crankcase pressure can drop fairly rapidly. In short, narrow ducts the velocity will rise alright, but the mass in the ducts will be small. And in long, narrow ducts the long plug of gas will resist acceleration and will only slowly come up to speed. Because long columns are such slow starters, the kinetic energy at the latter stage of transfer will only make up for what went missing at the initial stage.

P438

When unleaded became mandatory in 98 most teams had a hell of a time keeping deto under control, having to run very rich and retarded.
The cylinders with the straighter pipes always gave allot more grief, until a lowly dyno operator at Yamaha discovered that
when he stuck a large pressure probe into the header, the deto went away.
They managed to keep this secret for a couple of years but when teams like WCM got hold of the bikes, and left pipes lying about as you see in the pics, word soon got around.
The "things " intruding into the header take varying forms, but all do the same thing - the usually bottom "bent "pipes don’t have the same issue, so don’t need the so called deto buttons.
I have a couple somewhere from a Red Bull bike - I will pic them and post here .


Blowing a pipe,except for the initial header shape, looses power big time,as the angle changes are blurred.
HRC has the trick method of pressing the pipe in two halves, and welding the seams, as a press tool can imprint distinct "corners" where for example the mid joins the rear cone.
Years ago when working with Jim at JL I tried blowing the pipe into a split mould around the mid section, but even this lost around 2-3 Hp per pipe on Hines dyno at Zip,when testing his Superkart title engines.


A larger muffler ID exposes the wave fronts to more packing material area, thus reducing noise - a step back down from the perf core to a smaller exit tube will increase the wave amplitude and make MORE noise.
Stinger/muffler lengths/diameters are very hard to analyse, only way is to cut and try, but with small dia mufflers - generally shorter is better for power, but not noise.


One trick with earlyer TZ carbs was to remove the air corrector jet altogether, made them rev on way better with a slightly bigger main.

Re the muffler situation. - the small engines like a 125 have a completely different sonic signature to a 250 - you must use a DbA meter at a set distance every time.
I spent forever working weekends for the NZ Kart Federation with a Db meter hung above the track trying to find a way to quieten down the 250s.
On the meter the sound level was always less when using a bigger muffler core - to the ear it was alot "louder".
In the end we went to the ICC type muffler, with the front modified to accept the 32mm OD stinger.
This was a long 100mm tube with a 50mm core, and a 40mm outlet, thus a huge amount of absorption area, plus a resonant volume that cut high and low frequency noise considerably.
We got to the stage where the inlet was then louder than the exhaust - then we started work on carb inlet chambers and venturi nozzles etc.
The whole thing is super complex,and as usual what works to help noise - usually kills power big time - but the big diameter muffler stuck on the end of a 125 or 250 made no difference to power at all,when compared to the best small muffler, but no
way would this be practical on a bike..
A smaller muffler was always super critical on length and diameter, every change made a difference.


The most effective silencer I once made for a 125 cc kart had a length of 400 mm, an outer diameter of 80 mm and a core diameter of 35 mm.
Smaller core diameters did nothing for engine power and were worse in silencing. An end cap with a smaller exit diameter made more noise, just like Wobbly says.


I think its a good time to remind everyone that the whole reason we heard about the possibility that 30 Hp was feasible from a 100 bucket was due to the software I was using at the time.

Now, we plug TeeZees 125 Aircooled engine into the latest version of EngMod2T and voila we get a result.Gaining the experience to run the software effectively is time consuming - but nothing like the time it would take to learn the hard way, what not to do.

[Frits Overmars]

I wasn't sure because the engine could be run in either direction.Clue 1: turn the rear wheel and observe the clutch cage.
Clue 2: look at the curvature of the fan disc vanes.
Clue 3: look at the shape of the kickstart dogs in the center of the fan wheel.
Clue 4: push the starter button.
:devil2:

[TZ350]

Clue 1: turn the rear wheel and observe the clutch cage. Clue 4: push the starter button.


I tried, but how come the picture on my computer screen didn't move..... :scratch: ?????

[Sketchy_Racer]

anticlockwise. front pulley is fitted to end of the crankshaft itself so rotates at engine speed. at high ratio the rear pulley is doing engine speed times CVT ratio so it can be spinning pretty quickly.

Are you sure? After the clutch near the wheel is a gear set which i believe is only two gears so would reverse the direction, meaning if the motor ran anticlockwise looking at the photo the bike would go backwards also looking at the centrifugal fan the impeller shape would suggest that the motor runs clockwise. I am however, likely to be wrong.

[F5 Dave]

. . . and its the first time I have seen an RS chassis flapping the front wheel about as he changed direction coming down the hill,. . .

Oh yeah they totally do that if you crank up the rear & add some bumps as there isn't much travel. Taupo on the old track interconnect we used GP before last had the RS flapping like a beitch till I learnt to avoid those bump on the right of the track (once was enough). I'd previously seen the steering damper on DDips bike(s) & thought, you've got to be joking. . . . but I wasn't laughing after that, - he's a smart guy & Mt Wgtn is a goat track so it makes sense.

Last weekend I almost launched myself at Kaitoke with an ill timed application of gas in a low gear while changing directions put the front wheel down pointing the wrong direction. Decided not to do that again.

[FastFred]

Clue 1: turn the rear wheel and observe the clutch cage.
Clue 2: look at the curvature of the fan disc vanes.
Clue 3: look at the shape of the kickstart dogs in the center of the fan wheel.
Clue 4: push the starter button.
:devil2:

Can't see any kickstart dogs but the centrifugal fan looks like its curved for clockwise rotation, well its actually hard to tell as you can have forward or reverse curved blades.

[husaberg]

Timing marks works for me.........................

[ief]

How do you figure that? Or do clocks act differently on that side of the globe? ;)

[Frits Overmars]

How do you figure that? Or do clocks act differently on that side of the globe?Yes, they run upside down. But so do the locals, so everything falls into place.

Can't see any kickstart dogs but the centrifugal fan looks like its curved for clockwise rotation.I tend to agree on the fan vanes. And here's a little help re the dogs:

[speedpro]

Are you sure? After the clutch near the wheel is a gear set which i believe is only two gears so would reverse the direction, meaning if the motor ran anticlockwise looking at the photo the bike would go backwards also looking at the centrifugal fan the impeller shape would suggest that the motor runs clockwise. I am however, likely to be wrong.

The rear gear set has 3 shafts - input with the clutch, intermediate, and final which has the wheel mounted on it.

You can get intermediate shafts with different gears on and matching gears which can be pressed onto the input shaft to alter the final reduction ratio. They're listed on the link I posted for stupid cheap prices.

[TZ350]

274801
... here's a little help re the dogs:

Thanks, FastFred is blind as a bat and I didn't recognize the dogs and even now I can't see them clearly enough in the picture to make out which way they engage.

CVT's have not been that common here so I have not actually seen a CVT in real life only pictures like this.

You will be able to have lots of fun with us as the team and I flounder our way through this CVT thing .... its all good :D

[Frits Overmars]

Thanks, FastFred is blind as a bat and I didn't recognize the dogs and even now I can't see them clearly enough in the picture to make out which way they engage.My initial reaction (clue 1 - clue 4) was because I thought you were asking something about the engine in the picture. I did'n grasp that you were asking about the picture itself without having that engine at hand. And yes, the dogs in the picture are too small to recognize anything. I only pointed out where to look for them.

You will be able to have lots of fun with us as the team and I flounder our way through this CVT thing .... its all good :D
It pleases me especially that you guys are picking up on it.

[TZ350]

The rear gear set has 3 shafts ...

Thanks, like Sketchy I was unsure if it was 2 or 3.

274811

I can see that 3 keeps the motor turning in the conventional direction, the same direction as the wheels, being anticlockwise in this picture.

Do you know the overall input/output ratio of the reduction box?

I would like to run the variator clockwise on the right hand side of the bike.

My guess is that the variator front pully could be run backwards but the shoes and slots in the rear clutch pully mean it can only be run anti clockwise. Maybe the shoe assembly can be turned around and with straight slots the thing could be run clockwise too.

[Frits Overmars]

My guess is that the variator front pully could be run backwards but the shoes and slots in the rear clutch pully mean it can only be run anti clockwise. Maybe the shoe assembly can be turned around and with straight slots the thing could be run clockwise too.That ought to work. One thing to observe though: if the reduction gears aren't straight-cut, reversing the rotation may cause an unwelcome axial load on the bearings.

[TZ350]

... if the reduction gears aren't straight-cut, reversing the rotation may cause an unwelcome axial load on the bearings.

True but as I will be using 17" wheels and chain final drive I am not expecting to be able to use the original scooter gears and may need to make my own straight cut ones.

[speedpro]

Thanks, like Sketchy I was unsure if it was 2 or 3.

274811

I can see that 3 keeps the motor turning in the conventional direction, the same direction as the wheels, being anticlockwise in this picture.

Do you know the overall input/output ratio of the reduction box?

I would like to run the variator clockwise on the right hand side of the bike.

My guess is that the variator front pully could be run backwards but the shoes and slots in the rear clutch pully mean it can only be run anti clockwise. Maybe the shoe assembly can be turned around and with straight slots the thing could be run clockwise too.

You like making things hard for yourself. With straight slots, as suggested by Frits and therefore a more or less constant engine speed setup, it won't matter which way it rotates. Clutch engagement may be an issue. You won't be able to use a HIT clutch for instance. As for the axial loads, the only thing that will change with reverse rotation is the load will also reverse. You "might" have to make a beefier removeable gearbox side cover.

[wobbly]

And the reason you guys are shagging with a new final drive when you cant get the engine to last for a whole meeting is ????

[Frits Overmars]

True but as I will be using 17" wheels and chain final drive I am not expecting to be able to use the original scooter gears and may need to make my own straight cut ones.I can't wait :niceone:.

[TZ350]

And the reason you guys are shagging with a new final drive when you cant get the engine to last for a whole meeting is ????

Avoidance of Reality ........ :yes:

[F5 Dave]

That has to be the voice of reason.

[Frits Overmars]

And the reason you guys are shagging with a new final drive when you cant get the engine to last for a whole meeting is ????Every generation has to make their own mistakes, Wob. We old farts have had our share; now it's their turn. (Sorry, I forgot: you're younger than me :msn-wink: ).

[jasonu]

And the reason you guys are shagging with a new final drive when you cant get the engine to last for a whole meeting is ????

Fucking priceless!!!!! :laugh::laugh::laugh::laugh:

[TZ350]

We old farts have had our share; now it's their turn. (Sorry, I forgot: you're younger than me :msn-wink: ).

Ha ... yes Wob is younger but I think I am older than you..... :laugh:

[Ocean1]

[R RATED][/R RATED]
Ha ... yes Wob is younger but I think I am older than you..... :laugh:

Might be the one race I'd have a chance in.

[husaberg]

And the reason you guys are shagging with a new final drive when you cant get the engine to last for a whole meeting is ????

Mr Wob can you please pack up Vanessa's engine.
send us the price and i will transfer the funds..
I will sort the fitting and send it back after Xmas.
I am guessing its well past time, i pulled my finger out and actually did something.

[cotswold]

And the reason you guys are shagging with a new final drive when you cant get the engine to last for a whole meeting is ????

next time as I am running out of places to bruise.

[fatbastd]

Well, after being away from KB for years it seems there's a lot of reading to do! Just jumping to the end of this thread to see what's the latest, and flat out reading everythig to date - I'm up to page 80..: I'm knee deep in two strokes (all sizes) and had a bucket once (XL125S in a CB125T frame - only ever rode it at Ohakea, and it went well - apparently had been a very good machine)...anyway, watching with interest, as I might be needing a bucket soon!

[F5 Dave]

Whoa there big fellow. -coming up for four years on KB & this is your 5th post already? Don't want to wear it all out.

[speedpro]

He's been busy on Facebook

[fatbastd]

FACEBOOK, FACEBOOK, don't talk to me about bloody facebook!

Yeah, 5 posts...I noticed that too...I have tended to 'live' elsewhere, but am back now. Up to page 85...impressed at the level of effort and development going into what were poxy commuter streetbikes...I had a GP125 years ago - very early one that game with GT125 forks and wheels...gave it a pipe from Ziffle (with whom I worked at the time), and turned a left-handed RG250 pipe into a right hand GP125 pipe (man they're made of stern stuff - I nearly welded the peg to the pipe to save effort!) and it was a fun thing around the street, but would be blown away by what I see here...I know ehere it is, so might have to go and retrieve it!

FB

[fatbastd]

Further to my last, which I can't seem to edit, being essentially a Yamaha man, I had an RX125 years ago which went acceptably in the commuter role for which it was intended, but was a very sweet handler - I bought a frame later to build a bike into...another project that was short-circuited...only problem with the RZ engine was the Grand Canyon gap in the ratios between 3rd and 4th..right before I sold it I checked the ignition timing - for the first time (told you it was purely a neglected commuter) and it was MILES retarded..so I set it where it should have been and it flew! And the vibration promptly blew the headlight..

Anyway, back to vicarious bucket racing..

FB

[TZ350]

Further to my last, which I can't seem to edit,

Not enough posts.

I think you have to have at least ten before you can edit and maybe fifteen before you can delete one of your own posts.

Interesting story, I love hearing about the old school buckets, the guys who made them and how they did it.

[wax]

tz350 sorry been busy basking in the glory of the win and other stuff.
You can get straight cut gears for these gearboxes so no issue with wanting to do what you are planning. I will go talk to my friend tomorrow and try and sort you out some cases.

[fatbastd]

Yeah, these days, being a little more knowledgeable, I'm aware of where I can get gears to allow different internal box ratios, with one tooth either way with a 'bastard' gear - have done it on a couple of bikes (3 sets of ratios in one box- made it quite a pricey effort!) with excellent results. I'm also onto an man who likes gearboxes and has produced his onw 7 speed version for the bike he rides (not in NZ and not a bucket), so that he always has the right gear...no there's a though, assuming the rules are not restrictive to 6 speeds..

[husaberg]

Yeah, these days, being a little more knowledgeable, I'm aware of where I can get gears to allow different internal box ratios, with one tooth either way with a 'bastard' gear - have done it on a couple of bikes (3 sets of ratios in one box- made it quite a pricey effort!) with excellent results. I'm also onto an man who likes gearboxes and has produced his onw 7 speed version for the bike he rides (not in NZ and not a bucket), so that he always has the right gear...no there's a though, assuming the rules are not restrictive to 6 speeds..

Or you could just get a Cagiva Mito that comes std with a 7 speed (most models)
Some Sachs engines also had them and i think some mineraili engines.
Then again the CT110 has eight and i think some of the old Kawa 90's had 10 lol

come to think of it some of the suzi mountain goat engines had an duel ration 4 speed i think as well.

the KEL Kart Track Destroyer engine can have different gear ratios, using a combination of standard parts unfortuantly other than maybe just selecting a different gear ratio for a particular corner they don't offer much to close up all the ratios.(other than a lower 6th) like a higher first but then again they are at least 6 speed.

Vanessa has avaiable alternate gear ratios available from the NSR150 and the CRM125 which can provide a reasonable distribution of ratios but WOB says it won't need them anyway.
The biggest problem i found was the first gears on computer bikes are always too low unless o miles high gearing which efectivly makes them a 5 speed box.
My H100 had a Close ratio box 6 speed made up from "other" models of dubious legaliy........

[Ocean1]

i think some of the old Kawa 90's had 10 lol

Cousin had one, split 5 speed iirc. I did ride it, had a standard shifter and a sort of rocker on top of the case for the split but I can't for the life of me remember how you managed the thing.

[F5 Dave]

Very awkwardly, not the sort of thing you want to do heading into a downhill hairpin.

Wonder where Ziff is nowadays? Obviously moved from Marton, had to seen him at Boxing day races, but not for, erm well over 10 years I guess.

[miper]

and had a bucket once (XL125S in a CB125T frame - only ever rode it at Ohakea, and it went well - apparently had been a very good machine)...!

I wonder......Me and Phil Bird both had matching CB125T's with xl125s motors back in the late 80's early 90's in Palmerston north, and these went really well, for that time anyway. If per chance it was my old one then yes it did go very well. Won the local A grade champs on it 1990 ish much to the dismay of the two stoke boys. Phil was the master mind of the motors and spent many hours getting them reliably fastish. They were fun times back then.

[TZ350]

Won the local A grade champs on it 1990 ish much to the dismay of the two stoke boys.

Not much has changed then ......... :facepalm:

[TZ350]

274853

I have been trying to get a handle on the typical CVT's "gear" ratio range.

From what I can find out it appears to be something like 3.28 to 0.84 which happens to be pretty close to my Suzuki GP's gearbox. (if anyone has better info please let me know).

If 3.3 to 0.8 ish is right then this makes it really easy to adapt as all I need to do is fit the CVT's front pulley to the crank and fit the original primary reduction gears to the rear CVT pulley and run the front chain sprocket from what was the clutch gear.

It just can't get simpler than that.

[F5 Dave]

Not much has changed then ......... :facepalm:
That was once & not a GP. Certainly didn't happen again that Millenia. I think I bookended the Manuwatu champs (stopped about 2000 & something) on the Mighty H100.

[fatbastd]

I owned the CB125T/XL125S somewhere between 1992 and 11995. It was blue, with the original Comstar wheels, etc. Ignition died in the end and I sold it to a mate who fixed it.

[TZ350]

F5Tim

274855

Things are warming up in F5

274854

Different pipes, original Aprilia 50 Red line, Conti pipe Blue line.

A bit of work on the exhaust port and blow down STA should improve things a bit more.

Looks like a dangerous 10hp is a distinct possibility.

[F5 Dave]

Is that tail-piece a side cut Bucket? Very nicely done! Top marks.

[TZ350]

Is that tail-piece a side cut Bucket?

Yes a bucket for a Bucket. The front number board is the off cut from the bucket tail piece.

[Frits Overmars]

I tried to post a little technical story here to help you through the Christmas days, but I could not manage to insert the pictures the way I wanted to...
But in case you're curious, you might want to take a look here: http://www.pit-lane.biz/t3173p657-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-2#134197

[husaberg]

I tried to post a little technical story here to help you through the Christmas days, but I could not manage to insert the pictures the way I wanted to...
But in case you're curious, you might want to take a look here: http://www.pit-lane.biz/t3173p657-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-2#134197

Here is a little technical story for the coming Christmas days. Its official title is Transfer Theory, but I call it

<center>The leaning tower of Pisa<center>
<center>http://i15.servimg.com/u/f15/15/75/62/05/pisa_110.jpg<center>

<center>Transfer theory part 1<center>

<center>the central column<center>


We want ample angle.area for our transfer ports while at the same time keeping their height within limits, so we need all the transfer area we can get; we want to use as much as possible of the cylinder circumference.
The best way to utilize the available real estate would be to aim all transfers radially inward; that way the cross section widths of all ports would be equal to their chord widths and you can't get any better than that. All transfer streams would meet in the center of the cylinder, slow each other down and form a central column with only one direction to go: upwards, in the direction of the cylinder head.
But since you can't have a transfer port at the exhaust side of the cylinder, an imbalance would occur and that central column would be inclined (sic) to topple over towards the exhaust side of the cylinder. You don't want that because too much of the fresh charge would take the escape route into the exhaust duct without first scavenging the cylinder.

How do you prevent that central column from leaning towards the exhaust side? If you omit the transfer ports directly opposite the exhaust, you would restore the scavenging balance, but you would sacrifice too much valuable port area. There is a solution, but let me address some other scavenging aspects first.

We want as much transfer port area as possible, so it would make sense to have all transfer ducts enter the cylinder perpendicularly, right? Nope.
To begin with, most pistons are domed, so transfer flow entering the cylinder would collide with the dome. Aiming the transfer ducts axially at about the same angle as the piston dome, usually about 10°, will not cost any effective cross section area and it will noticeably improve the flow coefficient. Larger-than-zero axial angles at the port floors will also enable you to fit larger inner radii in the transfer ducts, another benefit for the flow.

Second: those transfer streams entering the cylinder and colliding in the center will convert kinetic energy into potential energy. In English: their flow velocities will slow each other down in the collision process and the static pressure in the middle of the resulting central column will be higher than the pressure in the transfer ducts.
That static pressure in the central column is a good thing: it will provide for a higher density of the fresh charge in the column and that helps to expel the hot, thin burnt gases from the previous combustion cycle. Think of it as using a jet of water to chase away smoke: that will work a lot better than the other way around (using smoke to chase away the water).

But the static pressure at the foot of the central column can also have adverse effects. Too high a static pressure will impair the flow, because the higher this pressure is, the smaller will be the pressure differential that accelerates the charge through the transfer ducts. Aiming the transfer ducts axially a little will improve the flow, just like it did because of the domed piston. Slightly axially-aimed transfer streams will provide for a less violent, not completely head-on collision. The central pressure can be controlled this way, and the transfer streams will keep the axial component of their velocity, so the central column does not need to begin its journey to the cylinder head with zero velocity. So the axial column speed can be controlled as well by the axial transfer angles.


Transfer theory part 2

positional & directional scavenging angles


Most two-stroke people define radial scavenging directions by quoting the distances where the ports would intersect the center line (the leading distance and trailing distance in the drawing below left). Gordon Blair used that notation in his publications, and 95% of us followed suit.
But there is a better, more universally applicable way.
I will explain with an example, not of scavenging directions but of port timing: I might say that a transfer port height of 13 mm is perfect for a racing engine. That may be true for a 125 cc engine but it would be nonsense for a 50 cc or a 500 cc.
But if I say that a transfer port timing of 130° is perfect for a racing engine, then that is valid for any engine, regardless of its cubic capacity. Absolute distance values (millimeters, inches etc.) are not suitable for universal guidelines. Degrees are, as are percentages of bore or stroke. Rpm values are not; mean piston velocities are.

I express transfer duct directions in degrees. Each duct has a leading flank and a trailing flank. Each flank intersects the bore at a point which I can define with a positional angle. And each flank hits the fore-aft center line of the bore with an included angle which I call the directional angle. The drawing below left may clarify what I mean. And the drawing on the right is an example of an existing cylinder.
Now we can express the radial characteristics of the transfer ports with positional and directional angles, regardless of bore and stroke.
And we can express the ports' axial characteristics with axial angles, but that only gives a 'universal value' for engines with identical bore/stroke-ratios.
We may quote a height H in the cylinder where the transfer port's roof would hit the opposite cylinder wall. But we need to express H as a percentage of the stroke. Then we will have a truly universal value.
Then we will also see that short-stroke engines require smaller axial angles.

<center>http://i15.servimg.com/u/f15/15/75/62/05/scaven10.png<center>

<center>Transfer theory part 3<center>
<center>the tower of Pisa<center>


As we are on the subject of scavenging angles, now would be a good time to say something about the axial angles of the A-transfers.
Surely a duct with an axial angle of over 20° offers a smaller cross-section to the flow than a duct that enters the cylinder perpendicularly?
Yes it does. But there are two good reasons to angle it upward anyway.

First, perpendicular mixture streams coming from the A-ports would collide and slow one another right down. The axial angles provide for less velocity losses and less pressure losses, so despite their smaller cross-section, upward ports may flow as much, if not more, than perpendicular ports.
(Now you may well ask why the B-ports do not get the same treatment. It is because the central scavenging column, resulting from all incoming scavenging streams together, must not have too much axial velocity, or the loop scavenging will result in a loop-loss into the exhaust).

Second, there is a thing called scavenging balance (I invented the word for my personal use, so this may well be the first time you ever saw it).
If you looked closely at the scavenging picture of the MB-cylinder I posted above, you may have noticed that the 'radial scavenging directional resultant' had a value of 101,045°.
90° would have meant 'straight up'; more than 90° indicates that the central scavenging column is leaning towards the exhaust side of the cylinder.
But we don't want that; it is bad for the scavenging of the rear part of the cylinder, and it is risky because it may provoke scavenging losses straight into the exhaust.

<center>http://i15.servimg.com/u/f15/15/75/62/05/pisa_210.jpg<center>


But how can we prevent a scavenging column from toppling over to the exhaust side like the leaning tower of Pisa? Not by pushing against its basis, but by pushing higher up. Hence the axial angle of the A-ports. The pictures will tell the story. (If only the Pisa architect had known a bit more about two-stroke scavenging....)

<center>http://i15.servimg.com/u/f15/15/75/62/05/pisa-s10.jpg<center>

<center>Transfer theory part 4<center>
<center>vectors<center>


Let us assume that all transfer ports are of the same height. Let's also assume that a port with twice the cross-sectional width will give twice as strong an impulse (that is already doubtful; it presumes equal densities and equal flow velocities in all ducts, and as duct contents can have different inertias, their accelerations may differ, as will their flow velocities at any given moment).

If you accept these assumptions, you can resolve each transfer stream into an axial component, a fore-aft component over the piston, and a left-to-right component over the piston. The axial components all work in the same direction: towards the cylinder head. The left-to-right components will cancel each other out (if they don't the scavenging is asymmetric) while contributing to the pressure creation at the root of the central column (which in turn will accelerate the axial flow and thus enhance the axial vector), and the fore-aft components will result in a vector that may either point towards the rear side of the cylinder, be zero, or point towards the exhaust side.
This fore-aft vector together with the axial vector will give a resultant that will lean towards the rear of the cylinder, or point straight up towards the head, or lean towards the exhaust side.

What we want to achieve, is an axial column that clings to the rear of the cylinder, so it can wash away the spent gases with as little turbulence as possible. Turbulence will result in mixing of fresh charge and burnt gases, and we don't need that. And mixing will heat up the fresh charge, bringing it nearer to the detonation treshold. And we certainly don't need that!

I realize this is a crude way of describing a complicated flow dynamics event, but hopefully it will help you form a mental picture (no pun intended).
<center>Merry Christmas and a Happy New Year<center>

[TZ350]

CVT Scooters with 16" wheels

274882

Does what make and model of scooter that has 16" wheels????

[wax]

cpi gtr
https://www.google.com.au/search?q=cpi+gtr&hl=en&tbo=u&tbm=isch&source=univ&sa=X&ei=uSDVUIauM4OjiQe_roCoCA&ved=0CDgQsAQ&biw=1536&bih=754

[TZ350]

cpi gtr
https://www.google.com.au/search?q=cpi+gtr&hl=en&tbo=u&tbm=isch&source=univ&sa=X&ei=uSDVUIauM4OjiQe_roCoCA&ved=0CDgQsAQ&biw=1536&bih=754

Thanks Wax

274883

If thats a 16" high profile road tyre, whats the bet a modified rim with a low profile racing 17" slick will fit in there.

[wax]

Your welcome. The downside is that your now swinging the whole engine as the swingarm and you have that unsprung weight to deal with

[TZ350]

The downside is that your now swinging the whole engine as the swingarm and you have that unsprung weight to deal with

:facepalm: arg, its never easy .......

[husaberg]

CVT Scooters with 16" wheels

274882

Does what make and model of scooter that has 16" wheels????

Suzuki Burgman has largish wheels if you are into that kind of thing.

Re the Frits post above if Frits hits reply with quote he will see what i did
my guess is your advanced options is not turned on? if not next to save is go advanced.
<center>i used a Code to center the pics<center>
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=274882&d=1356144386&thumb=1

To align the text option on the advanced panel selection.
to re-size pics i use this


<img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=274882&d=1356144386&thumb=1" width="340px"/>



<img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=274882&d=1356144386&thumb=1" height="180px"/>

Mr Mentaltrousers showed me how as he was sick of my over sized pics so thanks Mr T.

[Rick 52]

F5Tim

274855

Things are warming up in F5

274854

Different pipes, original Aprilia 50 Red line, Conti pipe Blue line.

A bit of work on the exhaust port and blow down STA should improve things a bit more.

Looks like a dangerous 10hp is a distinct possibility.

That is a great result, Tim must be happy with that, did you have to play with jetting ?

[TZ350]

That is a great result, Tim must be happy with that, did you have to play with jetting ?

No, just a basic play around to get a view of whats possible. Tim is going to tickle the cylinder to see what can be done with it.

[crazy man]

anyone know why on the run down of my 2 stroke it likes niping up? what do l look for ..thanks

[TZ350]

Husa pointed me towards some pictures of CVT racers on the Pit-Lane.biz site.

274892

Looking at the picture of this CVT racer it looks like there is no reduction gear box and that the front chain sprocket is behind the rear CVT pully and that they rely on the big rear sprocket to get sufficent overall gear reduction.

274893

Originaly I had thought of having the rear cvt pully driving a 3:1 reduction gear set but the big rear sprocket setup is much simpler. All I have to do is find a big enough rear CVT pully so I can have a low enough first gear for starting off.

[TZ350]

anyone know why on the run down of my 2 stroke it likes niping up? what do l look for ..thanks

This maybe the answer, or maybe not, food for thought anyway ....


Page 600 B

It seems that at high rpm and part throttle the pressure in the cylinder is higher than in the crankcase when the transfers open and hot burnt combustion gases back flow down the transfers.

Part throttle detonation is the current big issue for our 30+hp aircooled engine. Retarding the ignition on part throttle is only part of the solution.

More blowdown time area is required to lower the in cylinder pressure so opening the power valve further when closing the throttle at high rpm could be a solution.

Or the pressure inside the expansion chamber (and cylinder) could be lowered by having a second stinger pipe with a butterfly. Which is opened in high rpm part, throttle situations to drop the expansion chamber and cylinders working pressure.

And Frits proposes an idea where the intensity of the reflected wave is reduced by changing the size of the bleed venture at the end of the reflective cone.

Page 600 has quotes about this from Frits and Jan.

[Ocean1]

Looking at the picture it looks like there is no reduction gear box and that the front chain sprocket is behind the rear CVT pully and that they rely on the big rear sprocket to get sufficent overall gear reduction.

Worth noting that any form of conical pulley/belt drive is far less efficient than chain/sprockets, and the more force there is on a small drive pulley the more power will be lost in belt distortion/deflection. So making the bulk of your reduction in chain at the back wheel makes sense, even if it looks weird.

[crazy man]

This maybe the answer, or maybe not, food for thought anyway ....



Page 600 has quotes from Frits and Jan about this.thanks the one thing l have changed is the expansion chambers and was ok before . l know the stingers are not the best . bent up years ago so will replace them first

[speedpro]

Are these the bikes that don't have a variable rear CVT pulley? I think on these the motor pivots to compensate for variations in the front CVT pulley. The rollers instead of working against a spring on the rear CVT pulley work against a spring holding the motor against the belt.

[speedpro]

thanks the one thing l have changed is the expansion chambers and was ok before . l know the stingers are not the best . bent up years ago so will replace them first

You should be able to get someone to machine up a nice precision nozzle and then just use any old piece of tube to get the exhaust into the muffler. With a bit of thought you could have replaceable inserts of different size. I've tried different nozzles and got interesting results on the dyno.

[husaberg]

anyone know why on the run down of my 2 stroke it likes niping up? what do l look for ..thanks
My mussing is this.
On run down from high revs it will have high revs closed throttle closed throttle equals no fuel no fuel equals no oil.Plus the dyno drives the engine on longer than it would be on overun on the track.
I believe on the KTM 125 GP bike the solution was a injector to supply fuel on the Aprilia not sure. prossably a 45 kg physco rider that never backed of the throttle.They possibly did something tricky and secret...
i seem to remember Frits saying something about deto on overun as well.

[speedpro]

Closed throttle results in no air blowing through the engine so the oil stays there, more or less. Extended run down on a dyno is never good though which is one reason they should all have a roller brake.

[crazy man]

My mussing is this.
On run down from high revs it will have high revs closed throttle closed throttle equals no fuel no fuel equals no oil.Plus the dyno drives the engine on longer than it would be on overun on the track.
I believe on the KTM 125 GP bike the solution was a injector to supply fuel on the Aprilia not sure. prossably a 450 kg physco rider that never backed of the throttle.They possibly did something tricky and secret...
i seem to remember Frits saying something about deto on overun as well.that was my first thought but was ok before changing the chambers may do what speedpro says for starters and put the det counter on and see what its doing

[TZ350]

Are these the bikes that don't have a variable rear CVT pulley? I think on these the motor pivots to compensate for variations in the front CVT pulley. The rollers instead of working against a spring on the rear CVT pulley work against a spring holding the motor against the belt.

274894

Yes, looking at it you could be right, I don't know anything about them realy, just what I can surmise from the pictures.

274896

But I can't see where the spring would be.

274895

Here is a bunch of guys push starting their CVT race bikes, I didn't think you could push start a normal CVT so there must be something different about them like you say, and you maybe right, no rear clutch or rear variable pully.:scratch:

[wax]

Polaris atv are big on there cvt and so are snowmobiles.
Ebay motors may be your friend

[husaberg]

274894

Yes, looking at it you could be right, I don't know anything about them realy, just what I can surmise from the pictures.

274896

I can't see where the spring would be.

274895

Here is a bunch of guys push starting their CVT race bikes, I didn't think you could push start a normal CVT so there must be something different about them like you say, no rear clutch and variable pully, you maybe right.:scratch:

Are they like a Peugeot or similar moped pnly race class?

TZ the Husky and the Rokon both had reduction boxs, why...With the CVT you lose your primary reduction remember.............
if you are dead keen pn the CVT, i would suggest you make up a basic crankcase first like the one in the link Wax knows the one i mean...........
http://i44.servimg.com/u/f44/17/94/08/58/dscn1223.jpg

[TZ350]

i seem to remember Frits saying something about deto on overun as well.

274899

I can say hand on heart that the Beast has been known to deto on over run and part throttle.

[TZ350]

if you are dead keen pn the CVT, i would suggest you make up a basic crankcase first like the one in the link Wax knows the one i mean...........
http://i44.servimg.com/u/f44/17/94/08/58/dscn1223.jpg

Possibly a rear rotary valve like the Aprilia and a water cooled 100cc after market performance cylinder.

[husaberg]

Possibly a rear rotary valve like the Aprilia and a water cooled 100cc after market performance cylinder.

Hell no...... side sucker rotary valve..............like the RSW Aprilia Sorry jan and frits i are not sure why the RSA had a rear disk valve????

Was it just to slim up the engine and bodywork all that extra gears and intricacies make my head spin.................
I seem to remember a quote from Frits or Jan saying they wouldn't bother with the layout again i think because of the weight bias as well?

you could design one for the Air cooled GP cylinder and a LC performance cylinder
if it was made with a sandwich style construction you could make it like in the pic (but out of 4 sections of flat plate)
that way most of the basic cutting out could be done fast with a bandsaw. then only the final tidy up with a Mill.
<img src="http://i44.servimg.com/u/f44/17/94/08/58/dscn1223.jpg" width="340px"/>

[Frits Overmars]

Re the Frits post above if Frits hits reply with quote he will see what i did. ....Mr Mentaltrousers showed me how as he was sick of my over sized pics so thanks Mr T.Thank you so much for posting my Tower of Pisa-story, Husa; I think I'll stick to simpler things like two-stroke development :shifty:.
I hit that 'reply with quote' button and then for a fraction of a second your code was visible; I just managed to take a screenshot.

Husa pointed me towards some pictures of CVT racers on the Pit-Lane.biz site. Looking at the picture of this CVT racer it looks like there is no reduction gear box and that the front chain sprocket is behind the rear CVT pully and that they rely on the big rear sprocket to get sufficent overall gear reduction.
Originaly I had thought of having the rear cvt pully driving a 3:1 reduction gear set but the big rear sprocket setup is much simpler. All I have to do is find a big enough rear CVT pully so I can have a low enough first gear for starting off.

Are these the bikes that don't have a variable rear CVT pulley? I think on these the motor pivots to compensate for variations in the front CVT pulley. The rollers instead of working against a spring on the rear CVT pulley work against a spring holding the motor against the belt.

...But I can't see where the spring would be.

In the first picture you can see the horizontal spring, nested in the frame. The complete engine, including the pipe, is hung by the head (they do that to engines in France; for humans they have the guillotine).
The spring keeps the V-belt in tension. And in case you want to kick the revs up a bit when exiting a corner, there's a foot pedal with which the rider can put a bit more tension on the belt and thus force the primary heaves wider apart and lower the gearing.

But you don't want to go there, TeeZee. Only one heave of the front pully moves axially; the other front heave and both heaves of the rear pully are fixed.
That not only means that the range from shortest to longest ratio is only half of what it could be on a decent vario; it also means that the belt is forced to run skew most of the time.

[TZ350]

But you don't want to go there, TeeZee.

Thanks for the heads up ... interesting bikes though, great pictures.

[TZ350]

274906

Ok so that mounting is where they swing the engine assembly from.

[wobbly]

The RSA was developed due to Jan doing air flow tests on the RSW and finding that the rod position made a big difference .
Rear entry gave symmetric inflow and more power.
The engine position of the RSW was not as good as the RSA, and with more forward weight bias,many riders liked the feel of the older bikes front end, despite the RSA making more power.

[teriks]

I tried to post a little technical story here to help you through the Christmas days, but I could not manage to insert the pictures the way I wanted to...
But in case you're curious, you might want to take a look here: http://www.pit-lane.biz/t3173p657-gp125-all-that-you-wanted-to-know-on-aprilia-rsa-125-and-more-by-mr-jan-thiel-and-mr-frits-overmars-part-2#134197
Great christmas present!
Now thats a good start on a book..

[husaberg]

My mussing is this.
On run down from high revs it will have high revs closed throttle closed throttle equals no fuel no fuel equals no oil.Plus the dyno drives the engine on longer than it would be on overun on the track.
I believe on the KTM 125 GP bike the solution was a injector to supply fuel on the Aprilia not sure. prossably a 45 kg physco rider that never backed of the throttle.They possibly did something tricky and secret...
i seem to remember Frits saying something about deto on overun as well.

Closed throttle results in no air blowing through the engine so the oil stays there, more or less. Extended run down on a dyno is never good though which is one reason they should all have a roller brake.
Can anyone remember where the KTM 125 injector stuff is?


The KTM injection was Bartols way of preventing the engines from siezing on the overev during downchanges.
Pulling 15000 + with no air, and thus fuel, and thus oil, wreaked havoc with some riders, the injector squirted fuel/oil into the case when this was occurring.


Jan Thiel has retired and the two stroke era is over so the designers dont mind shareing info, all kinds of really good info!
KTM injection well thats a strange one even though their GP two stroke program is long gone that still dont talk or release photos (press releases aside). But yes I do know how it works, supplementary injection that feds into the crankcase to richen the mixture, just another approach to a power jet.


Thank you so much for posting my Tower of Pisa-story, Husa; I think I'll stick to simpler things like two-stroke development :shifty:.

Great christmas present!
Now thats a good start on a book..
Yes frits should write very many books with what i don't know.:laugh:

I hit that 'reply with quote' button and then for a fraction of a second your code was visible; I just managed to take a screenshot.
I will attach a word version with the bits highlighted


The RSA was developed due to Jan doing air flow tests on the RSW and finding that the rod position made a big difference .
Rear entry gave symmetric inflow and more power.
The engine position of the RSW was not as good as the RSA, and with more forward weight bias,many riders liked the feel of the older bikes front end, despite the RSA making more power.

yes i can remember that bit (afterwards) but the building of one if one was to have a go the increase in the complexity i don't think is worth the gain.
Yes in GP the extra cost and complexity it would be worth it,but for other classes i am not convinced. Certainly not for buckets.


http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=261462&d=1333621581

A technical explanation? Nah, too much to do today. But since you were kind enough to post that picture of your sex six sisters, I will show some curves of my own.
When Jan Thiel went to Derbi to design the bike we now know as the Aprilia RSA125, he encountered the 125 cc reed valve Derbi ridden by Lorenzo the previous season. Jan played around with the reed valver as well, because he wanted to find out the differences between reed valve and disk valve power. He managed to extract 2 HP more from the reed valver than anyone else had ever done before (never mind the fairy tales of reed valve 125s producing over 50 HP; those Horses must have been Shetland ponies, probably measured at the piston ring).
My graph shows the power curve for the Aprilia RSA, the Aprilia RSW and that best-ever reed valve Derbi. It's not quite in the same league as the rotaries, hmm?

EDIT: Shame on me; I discovered that I posted a wrong graph (and I do not have the correct one at hand here in Holland). Power curve DERBILOR shows the reed valve Derbi as Lorenzo rode it. After Jan finished playing with it, it had 49 HP. Still, the best-ever disk valver produced 10 % more power than the best-ever reed valver.

Rotary vs Reed =clearly worth it
Rear disk vs Side entry =not so much..ime

on the attachment bellow the arrow has slipped it should be in the column above if you hover your cursor there it will say align left ,center and align right you need to highlight the text or picture you wish to align first as well.

[trevor amos]

Very many thanks for your , in depth , technical treatise on transfer flow behavior and the controling influences , that the rest of us can only gues at . We are indeed very fortunate to have such an erudite tutor who has that rare talent to be able to offer difficult concepts and make it so accessable for us pupils !
So Frits , the only problem i can see is that we need more and more and more , and , given enough time , we might just get it ?

Warm seasonal greetings

[cotswold]

I got bored so stripped out the water cooled mb100 I bought a while ago. It was mentioned by someone that the motor may be over sized so I have put up a picture of the piston just to make sure before I decide what to do with it.
If any of you can tell by the numbers on the crown I would be grateful to find out the legality and also what it is so I can replace it. ( it has many dings looks like piston ring has exploded some time )

0.5 over
432 p2
cd

[Yow Ling]

I got bored so stripped out the water cooled mb100 I bought a while ago. It was mentioned by someone that the motor may be over sized so I have put up a picture of the piston just to make sure before I decide what to do with it.
If any of you can tell by the numbers on the crown I would be grateful to find out the legality and also what it is so I can replace it. ( it has many dings looks like piston ring has exploded some time )

0.5 over
432 p2
cd
Measure it across the skirt, 0.5 over what?

You should clear that up seeing as you named the previous owner in the photo !

[cotswold]

Measure it across the skirt, 0.5 over what?

You should clear that up seeing as you named the previous owner in the photo !

But I did clear him of any wrong doing as it was years ago he built it and as you know great grandads axe had many new heads and handles.

[Farmaken]

Wiseco listings show that as 54mm std bore +.5mm O/S = 54.5 mm

CD refers to the ring type

[husaberg]

I got bored so stripped out the water cooled mb100 I bought a while ago. It was mentioned by someone that the motor may be over sized so I have put up a picture of the piston just to make sure before I decide what to do with it.
If any of you can tell by the numbers on the crown I would be grateful to find out the legality and also what it is so I can replace it. ( it has many dings looks like piston ring has exploded some time )

0.5 over
432 p2
cd

Please note it's only called speedpros piston so I could find it in all my other junk and the piston came out of an engine he sold MANY MOONS ago and would have been changed many times since then........thought I should add that so if it turns out to be over, Rich won't be able to ramp up to Defcon 5 ;)


Measure it across the skirt, 0.5 over what?

You should clear that up seeing as you named the previous owner in the photo !

I cant tell much about that piston (is it single ring) the numbering looks kind of Wiseco like, but impossible to tell from the picture but is it forged? plain ring? dykes?
Before a motor is oversize the stroke has to be taken into consideration (Mike and i think now Dave) use larger diameter strike pistons that would be above the limit if they hadn't destoked first.

These strike kt100 pistons (http://www.strikeproducts.com.au/pistons.asp) are readily available in a huge range of sizes and are incredibly inexpensive We all should be using them except for the cost of destoking plus the engine will be less efficient as a non close to square bore and stoke.
Simple fact is 50-50.5mm 2 stroke pistons are not really manufactured any more and it is killing wallets and engines.

Dave had what 2 or was it 3 failures with NOS yz100 pistons these pistons have not been listed by Yam since i was at school.

I doubt Suzuki still makes RG400 pistons, either that only leaves kart pistons (but all the usable size ones have Dykes rings)
and other std road bike (not generally up to it)and Wiesco which are f-ing expensive.and not available freely or in oversizes.

The 2 stroke cc limit should be about 112cc lc 2 strokes vs 155cc four strokes and i have the technical data done for the FIM to support it. Infact i intend to submit a remit to the rules based on this.

[cotswold]

Measure it across the skirt, 0.5 over what?

You should clear that up seeing as you named the previous owner in the photo !

54mm across the skirt and it has been rebuilt many times since it was sold by it's original owner as he sold it with a 6 speed box now it has 5.

It seems like I need to strip it right down to check it has been de stroked and if not look out for a standard cylinder and just run the water cooled head?

Or put it on a shelf along with all my other garage art

[Frits Overmars]

The RSA was developed due to Jan doing air flow tests on the RSW and finding that the rod position made a big difference. Rear entry gave symmetric inflow and more power.
The engine position of the RSA was not as good as the RSW, and with more forward weight bias, many riders liked the feel of the older bikes front end, despite the RSA making more power.Fixed that for you, Wob. Typos do happen to the best of us :shifty:.

[jasonu]

There are currently 65 users viewing this thread!!!:niceone:

[speedpro]

"Please note it's only called speedpros piston so I could find it in all my other junk and the piston came out of an engine he sold MANY MOONS ago and would have been changed many times since then........thought I should add that so if it turns out to be over, Rich won't be able to ramp up to Defcon 5"

That's funny - Defcon 5.

The piston looks to have little dings from a broken little or big end cage, probably little end, from experiance.

I'm surprised it went to 54mm. Dave Diprose tried boring an MB out to 54mm years ago and went through the sleeve to aluminium in places.

Stock an MB of H100 is 50.5 X 49.5 for a capacity of about 99cc

With that piston at 54.5 X 49.5 gives a capacity of 115.5cc, just a smidge over the limit.

Dave has reduced the stroke to 48mm with the help of Yow Ling. His motor is now the same stroke as mine and he's running KT100 pistons around 52mm

With a piston at 52mm X 48mm gives a capacity of 101.9cc.

The cost of reducing the stroke using the method Dave used can more or less be recouped by using the cheaper KT piston and ring the first time. After that it's money for jam. Piston oversizes are in .05 steps which is just a hone which with the cost and the range of oversizes you may as well do every year, or more often.

Technically there is a few "legal" problems. Really you should use MB piston pin clips and not KT clips. I buy them by the packet of 10, MB clips that is. Dimensionally they are the same. Also the little end bearings. I've got some flash ones and when comparing them in the local friendly kart shop they look identical to KT100 little end bearings.

In case anyone is interested, I will be pulling my motor out of the chassis over Christmas some time. If anyone wants to drop round and have a look inside they're welcome.

[kel]

[QUOTE=speedpro;1130453648I will be pulling my motor out of the chassis over Christmas some time. If anyone wants to drop round and have a look inside they're welcome.[/QUOTE]

Count me in, but Im not interested in bearings. I tried having a sneaky look down the cylinder when the head was off at the GP, strangely the piston was locked at TDC. Can we take photos :lol:

[jasonu]

With that piston at 54.5 X 49.5 gives a capacity of 115.5cc, just a smidge over the limit.

.

The limit used to be around 106cc I thought. When did it change?

[husaberg]

The limit used to be around 106cc I thought. When did it change?

When its is air cooled and has a 24mm carb Jason...................:bleh:

As i have said before there Kevin Orrs is that size or bigger.....and legal... Thing is it is still giving away cc's
Grumph will confirm but is'n't it 117cc or close to that.

[F5 Dave]

. . .
I'm surprised it went to 54mm. Dave Diprose tried boring an MB out to 54mm years ago and went through the sleeve to aluminium in places.
. . ..

Actually I think he tried to get 125 & went through. I believe you can get out to about 118 with a 56, but then you go through. Yes Kevin's was undersize as is D.Cottons.




. . .
Dave has reduced the stroke to 48mm with the help of Yow Ling. His motor is now the same stroke as mine and he's running KT100 pistons around 52mm
. . ..
wrong Mike Mike, this Mike is in wgtn.

[husaberg]

Actually I think he tried to get 125 & went through. I believe you can get out to about 118 with a 56, but then you go through. Yes Kevin's was undersize as is D.Cottons.


wrong Mike Mike, this Mike is in wgtn.

Its not a very common name Dave.......

[TZ350]

Posted because someone asked where to find it all, so a recap on the basics of the Beasts Engine. Using Thread Tools and the View Thread Images option is a good way of finding interesting posts.


The exhaust open point has very little to do with creating power due to "pressure" on the piston for "longer" with lower timings.
The gas pressures soon after TDC ,that creates the real power, is up over 80 bar, the pressure at Ex open is a couple of bar at best.
Moving from 200* to say 190* creates jack shit extra exertion of pressure on the piston to create torque, that then creates HP.
But the real issue is that down at 190* duration we get a huge amount of superposition of the gas pulse exiting the exhaust, on top of the residual pressure at the port.
This adding of a new pulse on top of an existing residual pressure means the wave front running down into the header has a huge relative amplitude, and this creates a huge depression at the port around BDC.
This also means we have port/pipe resonance over a much wider range and at a much high higher level than can be achieved at 200* duration.
In a conventional design we are forced into a corner by needing to create as much BlowDown STA as we can, and raising the timing is the only available route.
This pushes us away from the ideal port/pipe interaction timings, but is a compromise we are forced to accept to create the + 200psi bmep's needed, to be competitive.
Just another small detail that many overlook, or are unaware of.

Some old links, to when we were setting up the port timing for the 30hp Suzuki GP125.


EngMod2T

For something different Page 400 is going to be the basic info for building a 30+hp Suzuki GP125 taken from the EngMod2T simulation files.

You will have to go to the original post to see all of the pictures and the complete text.


Ok .... this is where the simulated rubber hits the road.

We are going to see if we can make this.

Red line is my efforts with EngMod2T, Blue line is after Wobbly polished it up a bit and replaced the RS pipe with one of his own design.

Wobbly can provide the pipe dimensions or even one already cut out ready for welding.


Wobblys rule of thumb is, low and wide for the transfers to maximise blowdown time area which is usually in short supply on a single exhaust port cylinder like mine and if you have multiple exhaust ports Low and Wide allows a low exhaust port which helps keep the pipe in resonance for longer (wider power spread).

All the port timings are in this post


Ok ... ported the exhaust port.

I was able to clean up most of the damage around the exhaust port that happened a while back when a peg came out and allowed the ring to turn and catch in the port.

Exhaust timing on this one.




Next move is the inlet

Now to setup the compression ratio.

All the basic info for everything is displayed in the EngMod2T sheets.


I was thinking about more ordinary things like getting the transfers staggered just like Wobbly wants and the port entry windows in the correct ratio of 1.3 -1.2 and 1.1, and curved nicely. The inlet system the correct length and shape without humps and bumps and the workmanship for making a first class expansion chamber and all those imperfections that creep in, just basic stuff.


Here is a first shot at the GP125 with triple Ex ports Vs the single port version. You can see the big jump in blowdown pressure entering the transfers of the single port engine when in the overev region.

The single port is short on blowdown STA.


Wob, thanks for looking at my EngMod2T files.
I am not sure what I should allow for losses, I have used -12% on the RS graph and get 32 rwhp. I should get a chance to put it on the dyno in the next day or so, so fingers crossed and we will see how it works out.


Yes ... I found much the same, the triple port was not much better than the single when they both had to suck through a 24mm carb but when a biger carb was simulated the tripple produced more power up top and significantly more drive down low.

If they are both limited to a 24mm carb and similar power curves, then a good reason for making a tripple port cylinder would be for mechanical reliability with the triples main ex port width at 62% of bore diameter instead of the singles 75%.


Making progress
Measuring the squish clearance with a depth mike.
Skimmed a bit out of the head and got the clearance volume to 9.0cc spot on.



I was having a look at some Kart site about honing and they go a few steps further than I did

They bolt torque plates onto the cylinders and leave them for a few hours to let the cylinder distort
bolt an old header pipe and inlet stuff if applicable, and some hone the cylinder hot at about 350° F

http://www.ekartingnews.com/viewtopic.php?t=25643&postdays=0&postorder=asc&start=0


Torque plates are always a good idea - the aim of course is to finish up with as perfectly round a bore as possible.


Think it's even more gooder idea where there's bolts threaded into the cylinder, you've got the axial distortion from friction in the thread, it forces a sine wave shape into the cylinder wall.


Just washing in a cleaning bath is not good enough for long life and reliability.

How to clean a rebored and honed cylinder properly and know you have got it right.


Striped the engine down today after the Taupo GP


Tonights dyno effort ....

274967

OK so now we have joined the 30RWHP Club


The big hp engine has yet to prove itself.......

[Grumph]

When its is air cooled and has a 24mm carb Jason...................:bleh:

As i have said before there Kevin Orrs is that size or bigger.....and legal... Thing is it is still giving away cc's
Grumph will confirm but is'n't it 117cc or close to that.

It's around 115cc - that's enough at present.

I've been given another pipe to compare so it may be quicker yet....

[Buddha#81]

It's around 115cc - that's enough at present.

I've been given another pipe to compare so it may be quicker yet....

Have you stripped it after Grey? It wasn't overly fast at the S/R there were at least 3 4T's faster :msn-wink:

[husaberg]

Okay i alluded to this earlier on as per usual when i put something a side for later i can't find it:weird:

It was a piece written about 500 gp's
the FIM had asked two boffins to prepare and present a paper around the mid to early 90's one i think was dutch the other was English i think.

The formula they came up with was that given equal number of cylinders and open carburetors the fair size of engines 2 stroke vs 4 stroke was this.

360cc two strokes.
500cc 4 strokes.

If we were to break this down and compare to the current F4 sizes it gives this.
current rule.
Rule 24.2 3 F4 2 stroke max capacity for rebored engines 104cc
F4 4 stroke max capacity for rebored engines 158.09cc (note this was initially 130.5cc the 145cc then 150cc previously)

So to be fair, it should be 158.09 cc four strokes vs 113.82 cc 2 strokes of unlimited carb size.


Sorry TZ and other aircolled 125cc restricted carb 2 stokers. You can get plenty of 56-57mm pistons at the moment anyway.

As i said earlier this will allow the use of cheap, freely available KT100 pistons that are available in a number of sizes without the need to destroke.

These strike kt100 pistons (http://www.strikeproducts.com.au/pistons.asp) are readily available in a huge range of sizes and are incredibly inexpensive.
We all should be using them except for the cost of destoking plus the engine will be less efficient as a non close to square bore and stoke.
Simple fact is 50-50.5mm 2 stroke pistons are not really manufactured any more and it is killing wallets and engines.

Dave had what 2 or was it 3 failures with NOS yz100 pistons these pistons have not been listed by Yam since i was at school.

I doubt Suzuki still makes RG400 pistons, either that only leaves kart pistons (but all the usable size ones have Dykes rings)
and other std road bike (not generally up to it)and Wiesco which are f-ing expensive.and not available freely or in oversizes.

[Bert]

These strike kt100 pistons (http://www.strikeproducts.com.au/pistons.asp) are readily available in a huge range of sizes and are incredibly inexpensive We all should be using them except for the cost of destoking plus the engine will be less efficient as a non close to square bore and stoke. Simple fact is 50-50.5mm 2 stroke pistons are not really manufactured any more and it is killing wallets and engines.

Hold fire: you don't start a LC100 project with your eye's shut (it does require a little bit of preparation to resolve this).

Plently of Engines that would allow easy transformation to 100cc.
RG150: Bore: 61.00 mm Stroke: 50.60 mm (truck loads of these around).

TS125x/r: Bore: 56.0 Stroke: 50.6 mm
TZR125 / Derbi / Gilera: Bore: 56.4 mm Stroke: 50.60 mm
TZR150 tzm / dtr : Bore: 61.00 mm Stroke: 50.60 mm
Mito: 56 x 50.6 mm

Silly size more crank work required:
RS125 (aprilia): Bore: 54 mm Stroke: 54.4 mm
KR150: 59 x 54.4
NSR125: Bore x Stroke, 54 x 54.5 mm

these require less work in the sleeve (offering potentially better heat dissipation) but requires more work in the crank... trade-off's..

Piston wise:

Dave had what 2 or was it 3 failures with NOS yz100 pistons these pistons have not been listed by Yam since i was at school.
Was it really the piston, really??? (only Dave can answer that); and there are truckloads available if one actually go's looking (I just picked up 4 new pistons for $80 total shipped)..

including after market Wiseco & woosner for the vintage clan (early 80's RM100/KX100/YZ100 & even TS100 options); not forgetting they make a 48-51mm piston for new CR80/yz80's (for kart racing); and all these big bore options for scooters....google..... Dealing with the pin size requires finding one that fits your engine....


I doubt Suzuki still makes RG400 pistons, either that only leaves kart pistons (but all the usable size ones have Dykes rings)
and other std road bike (not generally up to it)and Wiesco which are f-ing expensive.and not available freely or in oversizes.
Yes, you can still order RG400 pistons (but you could buy 4 wiseco versions above). What's wrong with Dyke rings kart pistons??? or the strike pistons (KT100J)..

Online ordering ~70-$150 shipped to your door; while its a little more than a cheap ass Akunar for a FXR (you could order a AX100 and have the same result)....


The 2 stroke cc limit should be about 112cc lc 2 strokes vs 155cc four strokes and i have the technical data done for the FIM to support it. Infact i intend to submit a remit to the rules based on this.

Maybe submissions on rules should be undertaken via national committee.....
these larger options are already covered off with the 125cc rule and 24mm carb (weld some fins on)....
Because in reality if one was to start on two stroke, they are more likely to start with a TF/TS/DT/RX/GP aircooled engine; not start building a LC engine straight off the bat...

Unless CC reduction is in order ----> MX80's (not necessarily 85's), where there are a F##kload of parts still available cheap... while offers up a near 2:1 ratio between the 155cc four strokes vs. lc 2 strokes; with about the same power outputs (worked).

[TZ350]

275028 275029 275030

Ok Popped the bonnet on the Beast to find out why it nipped up at Tokoroa

275027 275031 275032

Light four corner seizure, but why???? ....:scratch:

[TZ350]

Probably figured it out.

2-Stroke running an unsuitable Cam

275035

No detonation.

275034

No charred oil on the underside of the piston, so not running to hot.

275036

Both Plug electrodes look ok, no melting on the edge of the center electrode and the earth strap looks ok too.

275037

To check the mixture one has to look deep down inside the plug and its easier to cut the insulator out of the plug body.

275033

This is what we are looking for, the area above the black line, and it looks neither rich or lean to me so I guess the mixture must have been ok for best power.

I think the seizure is due to using a piston with an unsuitable cam shape.

It looks like water cooled pistons are not that suitable for hotter running air cooled motors and forged pistons that grow more than cast ones are even more of a problem.

275038

<nobr>The piston is kept in alignment by the skirt, which is</nobr><nobr> usually cam ground (elliptical in cross section) (fig.12-16).</nobr><nobr>
This elliptical shape permits the piston to fit the cylinder,</nobr><nobr> regardless of whether the piston is cold or at operating</nobr><nobr> temperature. </nobr>

I think I will have to start looking at using a cast piston with a higher silicon content and giving it a bit more of a cam on the sides.

[Bert]

Unless CC reduction is in order ----> MX80's (not necessarily 85's), where there are a F##kload of parts still available cheap... while offers up a near 2:1 ratio between the 155cc four strokes vs. lc 2 strokes; with about the same power outputs (worked).

continuation....

A good MX80cc (pre powervalves engines) engine might put out 18Hp if ya really lucky (20-21Hp with some effort), power valve engines ~20hp (26-28hp maybe with some serious effort).
Most people racing FXR's (at the pointy end) are putting on exhausts, carbs & some are doing cams; resulting in around 19-21Hp; serious effort gets to ~24Hp and all the torque under the sun (its nearly always FXRs up the front with less power than some of the two strokes)..

While F5dave (or others) is bound to post "Flogged out MX bikes" the reality is most engines now used by two stroke bucket racers start there life as flogged out anyway (its a lottery).

Stuffed mx80 Bores are the problem (but re-plating by nzcylinders (http://www.nzcylinders.com) is going to be cheaper for the masses than sleeving a rare 125 down).
The rest of the parts are on par with currently available engines in use.
Anyone serious about building an engine is going to do the mains, rod & piston anyway (no matter what motor it is) and its not much more effort to do the rest of the bearings in the engine (or find another gearbox)....

if people are really serious about rule changes; then I believe (and others have posted this over the years) 80's really need to be considered (with some restrictions)? things that can be measured easily; exhaust duration & carb size. simple.

Sorry TZ for filling up your thread with this...

[cotswold]

275028 275029 275030

Ok Popped the bonnet on the Beast to find out why it nipped up at Tokoroa

275027 275031 275032

Light four corner seizure, but why???? ....:scratch:

I reckon we still had it too lean.

[Bert]

Probably figured it out.

2-Stroke running an unsuitable Cam

275035

I think the seizure is due to using a piston with an unsuitable cam shape. It looks like water cooled pistons are not that suitable for hotter running air cooled motors and forged pistons that grow more than cast ones are even more of a problem.

I think I will have to start looking at using a cast piston with a higher silicon content and giving it a bit more of a cam on the sides.

What about re-profiling/dressing the pistons on the four corners?
reading about old two-stroke race engines; it wasn't uncommon to read about running the engine in (bring it up to temp), then stripping them down to take the high rubbing spots off the pistons (with wet and dry).

Not that long ago there was an interesting article on Hugh Anderson and his time as a works rider; he discussed personally dressing pistons due to their production shape late at night (when he thought everyone was asleep); only to have the suzuki mechanics somehow replace them before racing the next day--- resulting in seizures (due to suzuki's endless quest for tight tolerances for top housepower).

I was surprised with the clearance specs for the Wiseco pistons (YZ100 aircooled pistons) which I assumed was to deal with these issues (well larger than LC specs); forged piston expansion rates etc (I ended up splitting the difference). even then, I still need to dress mine in the TZR around the same spots.

[Kickaha]

reading about old two-stroke race engines; it wasn't uncommon to read about running the engine in (bring it up to temp), then stripping them down to take the high rubbing spots off the pistons (with wet and dry).
That's not just for old two stroke engines, even on my 95 TZ250 that was recommended

[cotswold]

Probably figured it out.

2-Stroke running an unsuitable Cam

275035

No detonation.

275034

No charred oil on the underside of the piston, so not running to hot.

275036

Both Plug electrodes look ok, no melting on the edge of the center electrode and the earth strap looks ok too.

275037

To check the mixture one has to look deep down inside the plug and its easier to cut the insulator out of the plug body.

275033

This is what we are looking for, the area above the black line, and it looks neither rich or lean to me so I guess the mixture must have been ok for best power.

I think the seizure is due to using a piston with an unsuitable cam shape.

It looks like water cooled pistons are not that suitable for hotter running air cooled motors and forged pistons that grow more than cast ones are even more of a problem.

275038

<nobr>The piston is kept in alignment by the skirt, which is</nobr><nobr> usually cam ground (elliptical in cross section) (fig.12-16).</nobr><nobr>
This elliptical shape permits the piston to fit the cylinder,</nobr><nobr> regardless of whether the piston is cold or at operating</nobr><nobr> temperature. </nobr>

I think I will have to start looking at using a cast piston with a higher silicon content and giving it a bit more of a cam on the sides.

Never would have thought of that but makes sense when you look at piston clearances on old school air cooled motors and compare them to w/c ones.

Just stole this from vintage mx site,
for an iron bore (not nikasil) .0025-.0035" clearance is good, .005" too much. Nikasil bores are .0015-.002" for motocross bikes. Measure the bore with a bore gauge top and bottom, front to back and side to side, 4 measurements to make sure the bore is within .0002-.0004" round. Measure the piston with a mic (not a caliper) at the widest point of the skirt.
Pistons are machined with a taper in the skirt so the diameter at the crown is smaller than the diameter of the bottom of the skirt. This is because when engine is hot the crown of the piston is hotter than the bottom of the skirt so it expands more and the piston becomes more cylindrical as heat removes the piston's taper. That makes it critical that you measure the piston in the correct location.

[husaberg]

Hold fire: you don't start a LC100 project with your eye's shut (it does require a little bit of preparation to resolve this).
you chose the Honda; it requires less work in the sleeve (offering potentially better heat dissipation) but requires more work in the crank... trade-off's matey. not worried about the crank work cause my one will still require destroking regardless


Was it really the piston, really??? (only Dave can answer that); and there are truckloads available if one actually go's looking (I just picked up 4 new pistons for $80 total shipped)..
Some of old stock ones at the moment, no more being made if you are talking about rm100 and yz100 or will ever be made the demand is not there.......

including after market Wiseco & woosner for the vintage clan (early 80's RM100/KX100/YZ100 & even TS100 options); not forgetting they make a 48-51mm piston for new CR80/yz80's (for kart racing); and all these big bore options for scooters....google..... Dealing with the pin size requires finding one that fits your engine....
Yes currently Wiesco and woosner make vintage pistons, but for how long the demand get less every year Brent and at what cost
the os 85 to 100cc piston (i have one btw) are 3 times the cost of a similar strike piston and are not available in any more oversizes


Yes, you can still order RG400 pistons (but you could buy 4 wiseco versions above). What's wrong with Dyke rings kart pistons??? or the strike pistons (KT100J)..
The supply of RG400 pistons will dry up very soon...it was a jap export only model made for only a few years ask yourself how long Suzuki will keep making them for.
Dyke rings when was the last time you seen one used in a GP engine 20-30 years ago ask yourself why?
The KT100j has an acre of area on top of the gudgeon. Mike has a pic of one i will add it)it was posted on the thread. Getting it to work in an engine other than a KT100j would be interesting........
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=241981&d=1309594255
I are not sure why your reply carries so much vitriol but regardless why not argue with the maths....
of Dr Jeffery Rowe (Manchester University) and Dr Hans Von der Marwitz (BWM) (whoops i guess that make him German rather than Dutch)
they are the ones that were given the brief to come up with the formula by the FIM and came up with 360cc 2 strokes vs 500cc four strokes..

As for 80cc MX... No way it would make other 2 stroke engines obsolete overnight, makes no sense to me, to do that.
AS i said the origional 4 stroke size was 130 the 140 then 145 then 150 now 158cc the two stroke f4 has never moved the 150's have been great but there is not a long term viable 50-51.5mm piston but there is an option to even up the cc rating to what they should be.
As the four stroke crowd keeps pointing out the two strokes aren't matching the 4 strokes results at the moment...

[F5 Dave]

Hold fire: you don't start a LC100 project with your eye's shut (it does require a little bit of preparation to resolve this).

Plently of Engines that would allow easy transformation to 100cc.
RG150: Bore: 61.00 mm Stroke: 50.60 mm (truck loads of these around).

TS125x/r: Bore: 56.0 Stroke: 50.6 mm
TZR125 / Derbi / Gilera: Bore: 56.4 mm Stroke: 50.60 mm
TZR150 tzm / dtr : Bore: 61.00 mm Stroke: 50.60 mm
Mito: 56 x 50.6 mm

Silly size more crank work required:
RS125 (aprilia): Bore: 54 mm Stroke: 54.4 mm
KR150: 59 x 54.4
NSR125: Bore x Stroke, 54 x 54.5 mm


This is like shooting fish in a barrel.

ok, its like this: RG150, most of these have been snaffeled up but streetstock racers. I've had people from Auckland ringing me in the hope I'll know of one tucked away that hasn't got knackered cases (surprisingly common).

Everything else listed: erm, c'mon - never sold in NZ, so you're looking at ebay in the hope you won't get hung out & still have to pay a crazy shipping price.

Whereas there are still a several models (TS100, TF100, GP100, MB100, H100, A100 etc) that could spring a new lease of life with a cheap KT piston. 107cc would be all that was required & leave a few O/Ss.

[F5 Dave]

. .
While F5dave (or others) is bound to post "Flogged out MX bikes" the reality is most engines now used by two stroke bucket racers start there life as flogged out anyway (its a lottery).
...
yup damn right I will. Street bikes are lower spec'd & last & last. MX bikes are raced & then sold & then used as trailbikes, sold & then thrashed till they die in a million bits. The only way you'll get one is a running bike. Less & less 80s about. May as well run 85s, who could tell the diff? Then may as well buy a latter model one. Cost of racing goes up.


Ah heck I'm feeling complacent, maybe it would be easier, I'd love to race one.

[husaberg]

Whereas there are still a several models (TS100, TF100, GP100, MB100, H100, A100 etc) that could spring a new lease of life with a cheap KT piston. 107cc would be all that was required & leave a few O/Ss.

its not that often we agree, still don't totally. I feel the cc i feel need to go to about 112cc.
Why to allow for al these other bikes you quoted that are 50.6mm stroke rather than the MB100 49.5mm hense a few more cc
if 1mm oversize which is not over the top in my opinion so that makes 53mm
53mm bore x50.6mm stroke =111.63
it is still well within the formula below.

[wobbly]

Several observations from the pics.
It is detonating - or more likely pre igniting.
Look at the middle of the piston crown, there are speckles all around this area, only one thing does this.
The crown has a white sheen to it, its too lean at some point in the fuel curve.
It should be light coffee brown, everywhere, for optimised AvGas
There is a dark area over the Ex port, this implies the engine has crap scavenging and has alot of short circuiting, or the stinger is too small.
The A transfer rearward radial angle may be too steep, allowing direct looping into the EX when at BDC - the stinger size is a little harder to optimise, being a very high specific output air cooled
and very little anecdotal evidence to point you in the right direction.
Having no marking under the crown, doesnt mean it isnt over heating, in this case it isnt being overheated for long enough, and you are probably very close to optimum ignition timing,where as
over advanced would colour up the underside alot quicker.
The spark plug - why are you running a 9 in a Super Hot air cooled engine that is always going to be running up against the fins thermal ability to reject heat fast enough.
A KT100 making 18 Hp with more finning than you have will tolerate a 9 plug - just.
That is the reason there is no distinct burn line on the porcelain - as ALL of the porcelain is running too hot for an oil zone to form, and give you a reading.
I would be fitting a 10.5 - this is what the 28 Hp, 22,000 rpm 100cc air cooled kart engines HAVE to run or they seize instantly.The end of the earth electrode is blasted clean - that is heat induced deto, or as I said at the beginning, maybe this is causing pre - ignition.

[Bert]

Maybe this should have been restarted in the thread started by Skunk last year..


I are not sure why your reply carries so much vitriol but regardless why not argue with the maths....

As for 80cc MX... No way it would make other 2 stroke engines obsolete overnight, makes no sense to me, to do that.
As the four stroke crowd keeps pointing out the two strokes aren't matching the 4 strokes results at the moment...

Not meant to be; just presenting another side of the argument (being one that has ran out of oversizes on a TF in the past; and has done a 125/100 conversion).
Maths: Not to be an ass but what are the constraints / brief / specs and formula behind the resulting figures; to enable the formula to be scaled down to F4 (opps: read the article now; but still no real answers).

Yes you have a point about supply and demand, but I guess it depends on how long you want the rules to be valid for.
80's, with the right formula I don't believe they will make other engines obsolete any more than lifting the CC size for 100's for those with 125's.


This is like shooting fish in a barrel.
Everything else listed: erm, c'mon - never sold in NZ, so you're looking at ebay in the hope you won't get hung out & still have to pay a crazy shipping price.

Whereas there are still a several models (TS100, TF100, GP100, MB100, H100, A100 etc) that could spring a new lease of life with a cheap KT piston. 107cc would be all that was required & leave a few O/Ss.

Dead fish; but I have seen most of them sold (likely one off imports) over the past few years on trademe. but yes your point is valid (and we have discussed this previously).

I don't really disagree about new life into old air cooled 100cc engines where re-sleeving becomes far too expensive; its just the LC 100's in relation to the 125's

But deep down; I'd just love to race a 80/85cc against a 150cc fours; I could image it could appeal more to the XYZ gens...

once again sorry TZ; I'll stop now.

[kel]

Several observations from the pics.

Great post Wob!

A big thanks and a Merry Christmas to Frits, Wob and all the other contributors that make this thread such an informative and rewarding read. :sunny:

[TZ350]

Thanks Wob


Several observations from the pics.
It is detonating - or more likely pre igniting.

275045


Look at the middle of the piston crown, there are speckles all around this area, only one thing does this.
The crown has a white sheen to it, its too lean at some point in the fuel curve.

It should be light coffee brown, everywhere, for optimized AvGas.

There is a dark area over the Ex port, this implies the engine has crap scavenging and has alot of short circuiting, or the stinger is too small.

The A transfer rearward radial angle may be too steep, allowing direct looping into the EX when at BDC - the stinger size is a little harder to optimise, being a very high specific output air cooled and very little anecdotal evidence to point you in the right direction.

275046


Having no marking under the crown, doesn't mean it isn't over heating, in this case it isn't being overheated for long enough, and you are probably very close to optimum ignition timing, where as over advanced would color up the underside a lot quicker.

275047


The spark plug - why are you running a 9 in a Super Hot air cooled engine that is always going to be running up against the fins thermal ability to reject heat fast enough. A KT100 making 18 Hp with more fining than you have will tolerate a 9 plug - just.

275048


A hot air cooled engine that is always going to be running up against the fins thermal ability to reject heat fast enough ... That is the reason there is no distinct burn line on the porcelain - as ALL of the porcelain is running too hot for an oil zone to form, and give you a reading.

For 10,5's I will have to do a 3/4" reach conversion.


I would be fitting a 10.5 - this is what the 28 Hp, 22,000 rpm 100cc air cooled kart engines HAVE to run or they seize instantly.The end of the earth electrode is blasted clean - that is heat induced deto, or as I said at the beginning, maybe this is causing pre - ignition.

275050

:facepalm: ... and I thought the 9's were going to be to cold but Ok as luck would have it, I have one or two 10's (good old Ebay), so B10's it is.

[Haufen]

275028 275029 275030

Ok Popped the bonnet on the Beast to find out why it nipped up at Tokoroa

275027 275031 275032

Light four corner seizure, but why???? ....:scratch:

Is that a crack in your cases above the inlet port? Lower right picture, right side.

[F5 Dave]

. . .
Having no marking under the crown, doesnt mean it isnt over heating, in this case it isnt being overheated for long enough, and you are probably very . . . .
also I guess having that hole drilled in the piston might clean up that area.