ESE's works engine tuner [Archive] - Page 6

TZ350

27th August 2009, 21:57

What I'd be concerned about is that the retarded ignition gets the revs pretty high for an old suzi crank. But clearly there would be a nice gain in a curve closer suited between the two.

The crank is pretty beefy with high speed industrial twin row self aligning phenolic caged main bearings. A 22mm big-end (up from 19mm) and a Yamaha RD350 rod with oiling slots hand cut into it with a small slotting blade in a 4" grinder. The big-end itself is a RGV unit as is the little end.

But yes 11-12K is a bit much and way past what the teeny weeny 24mm carb can properly pass.

The inlet port time area for a 24mm carb and inlet port/timing combo worked out good for 9500 to possibly 10500 at a stretch.

My plan was to tune for 10500 or a bit less, some how its crept out to 12,000 and must be getting strangled by the carb.

Give me a day or three and I will do a Time Area Analysis of the ports and write up the chamber dimensions.

I figure if I could get it peaking at 10k I could possible keep the hp and have a wider power band.

The best bike so far in the Team ESE group is the GP that's been modified the least. 1.75mm of the barrel, and "O" ringed, RG250 chamber and KX80 ignition, no other changes. It would be interesting to compare time areas with it.

.

TZ350

27th August 2009, 22:17

Save the stuffing around and go buy one of these http://www.ignitech.cz/english/aindex.htm

I hear you, I have even visited the sight and checked them out. I havent given up on my RM setup completely yet but I am starting to have my doubts.

.

bucketracer

27th August 2009, 23:04

.

The best bell mouths are those that are short and fat! http://www.profblairandassociates.com/pdfs/RET_Bellmouth_Sept.pdf

.

TZ350

28th August 2009, 17:29

Some interesting links and down loadable PDF's I came across while looking for Gordon Blairs book on designing 2-strokes.

Links

4-Stroke valve spring design
http://www.profblairandassociates.com/pdfs/RET036_Blair.pdf

Pneumatic vs Steel valve Springs
http://www.profblairandassociates.com/pdfs/Steel_Springs_Vs_Gas.pdf

Acceleration testing of a 2-Stroke
http://www.2stroke-tuning.nl/media/artikelen/2takt_dyno_blair.pdf

Tuning a cart engine exhaust
http://www.bkarting.com/tech-docs/expchmbr.pdf

Advanced 2-Stroke tuned exhaust design
http://www.freewebs.com/jsu_tiedostot/pdf/2003exhaust.pdf

Intake bell mouth design
http://www.profblairandassociates.com/pdfs/RET_Bellmouth_Sept.pdf

Designing a race 4-Stroke
http://epubl.ltu.se/1402-1617/2006/099/LTU-EX-06099-SE.pdf

Small 2-Stroke direct injection retro fit.
http://www.envirofit.org/media_docs/publications/SAE%20SETC%20Design%20of%20a%20Direct%20Injection% 20Retrofit%20Kit%20for%20Small.pdf

A look at the books ava for designing and testing engines
http://store.sae.org/catalog/powertrain.pdf

And I am still looking for Blairs Book.
.

bucketracer

29th August 2009, 09:46

A whole bunch of articles from Gordon Blair in Race Engine Design mostly 4-Stroke, so more for the FXR boys.

http://www.profblairandassociates.com/RET_Articles.html

PS Gordon Blairs book on basic 2-stroke design refers to the returning pressure wave in the expansion chamber as a "Plugging Pulse".

I have seen plenty of references to "Supercharging" but that is the first time I have seen it referred to in any literature as a plugging pulse.

.

TZ350

29th August 2009, 10:16

.

Another from G Blair on 2-stroke direct injection. http://www.etsmtl.ca/zone2/clubs/quiets/ets_ic_design_paper_2009.pdf

.

bucketracer

29th August 2009, 10:24

.

Lots of interesting Vid Clips of DIOSpeedDemon porting and developing his motor the Gordon Blair way.

http://www.youtube.com/user/DIOSpeedDemon

.

TZ350

29th August 2009, 10:31

.
"The work by Blair, Kenny and others at QUB showed that the velocity of the gas across the width of the transfer port was virtually constant, but that the direction of the gas stream varied at all points in the cycle.

For a test cylinder, having a transfer port height of 12 mm the results were

Port open..Angle one Angle two
.......mm...(Horizontal)(Vertical)
Fully open
........12.....10.....14
........10.....10.....16
........8......14......19
........6......18......26
........4......21......33
........2......25......34
........0......-........-
where "angle one" is the horizontal divergence of the gas stream away from the port direction towards the exhaust port (Fig 10 ), and "angle two" is the vertical divergence of the gas stream away from the port direction upwards towards the cylinder head (Fig 11 ).

We see that the flow bends upwards and forward towards the exhaust port as the cycle proceeds and the piston rises to shut the port. In their experiments, Kenny, Blair et al tested six different transfer shapes, the best two are presented here. Shape "A" (Fig 12 ) gave the best performance at all rpm, but was only marginally (2% - 3%) better than shape "B" (Fig 13 ), which is very similar to the shape of most Japanese ports, and is more easily achieved adapting an existing cylinder than shape "A". "

Abstract taken from http://www.lortim.demon.co.uk/vsih/pistons.htm

.

Chambers

29th August 2009, 20:49

The team ESE bikes are making enough power but the handling is letting us down and my bike is too hard in the back-end and bounces all over the place going over bumps.

I have a set of good shocks but no idea of the spring rate. So I have to figure out what they are so I can get some softer ones.

This is the setup I lashed together to measure how many Kg/center meter they are. The scales are preloaded to 10 Kg with the spring in place then the press is used to crank on another 10kg. The distance the spring collapses is measured under the 10kg load and with a bit of simple arithmetic we can workout the Kg/mm Kg/cm lbs/inc or whatever.

Tuti spent a happy couple of hours measuring all the springs we could find.

.

SS90

30th August 2009, 01:22

As it turned out the power/torque curve with the retarding ignition was worse in every way compared to the fixed ignition except at over rev. I guess the amount of retard (about 15deg) with this ignition is too much to be able to get it right at both ends of the rev range.

The one exciting point is the 500rpm over rev at the top. I will try this retarding idea again with a unit that has less retard, maybe 5-7deg.
What I would like is the fixed ignition curve to 10,500revs then have the retard kick in for over rev to 12,000.

.

I havn't found the same / similar results as this in my experience Teezee, so I have to think the same way as Sonic V.

The correct curve for any given engine really is different to the next.

As a VERY rough guide (gulp) I suggest that such an ignition curve would be good for chambers engine, with it's "non squish" head, and "old school" expansion chamber.

Because you have a "squish head", the curve you will end up finding suitable will be somewhat different for something, that for example, has a "non squish" head.

When I started looking at ignition curves, I spent a bit of time looking at what japanese manufacturers where doing in the early to mid eighties (when all the "new generation" stuff was made available to the public)

A good one to look at is the Yamaha RZ250R.

The cylinder head design is essentially the same as Chambers, and the expansion chamber is not to far removed either.

On RZ's (I can try and find the curve if you need it) the ignition curve is essentially the same as the one you have just tested.

And don't forget the RZ's had power valves..... the is a direct corrolation between high retard ignitions, older pipe designs,non squish heads and power valves.

The cylinder head design and the variable swept area/trapped compression is the main reason

The difference being that, because it is for a "road" bike, it runs 17 deg in the lower RPM, (better idle) and advances up to (I think) 25 deg at 7,000 and retards back to 5 deg at 11,000 (from memory)

Holding static at 25 until 7500 RPM would work just the same, albeit a crap idle.

My experience has shown that, when using a "squish head", while the turbulence increases with RPM (suggesting more retard is needed), it seemed that many other factors influenced the curve that best suited, and less retard that I predicted was required!

As SonicV pointed out, the exhaust pipe pays a BIG part in the suitable ignition curve, as does cylinder compression, head design,scavenge patterns and swept area (trapped compression)

I have found that because I get the best results (rideabilty wise) when I use non squish head design, the engines I build like quite a bit of retard (the same as you have on your test engine essesentially) and, as I have my own "fomula" for building 125cc two strokes, I know how to build an engine that benefits from such a curve.

With your engine, much like you suspect, I agree that more like 7 deg retard would be suitable (most likely).

In some parallel universe, where you HAD to run that ignition, you could build an engine that was more suited to that curve, but obviously it is sensible to try a different ignition!

bucketracer

30th August 2009, 03:04

.

I hear Chambers and TeeZee spent the day up at Johns dyno and Chambers bike makes the same power and torque curve as the two front running CB125 4-strokes.

.

SS90

30th August 2009, 03:21

.

Lots of interesting Vid Clips of DIOSpeedDemon porting and developing his motor the Gordon Blair way.

http://www.youtube.com/user/DIOSpeedDemon

.

Sorry to distract from the point of this thread Teezee, but I though we could all do with a bit of a laugh........

Following the thread link to youtube was the funniest thing I have done it months..... The following is a screen scrape from "Diospeedemons" description

A 28mm feeding a 30mm creating an ENORMOUS VELOCITY EFFECT at pinnacle of peak power. This is an experiment so far with synchronized throttle slides and blue-printed and balanced cylinder specs. The carbon reed valve is variably controlled manually, to optimize maximum intake and flow control.The reed cage has been radically redesigned to make the boyesen reeds emulate the function of timed valves. With this in place, an over-pressure condition can be created in the intake system, thus making True Supercharging possible. I have found a way to retard the ignition timing, under supercharged condition to minimize the effects of detonation.The vacuum guage will be installed to monitor overpressure and a K and N fuel/air meter with oxygen sensor built into phongeer exhaust, will monitor the best fuel-air ratio I can possibly attain. A Daytona electronic tachometer will help me fine tune the Boost Effect, then I will install on-demand Alcohol/Water injection using MCmaster-Carr brass misting nozzles at 1.5 gallons per hour. Water injection has been known to cool the intake incoming fuel charge, thus allowing more condensed fuel and air into the cylinder for a bigger bang= creating more horsepower. Denatured Alcohol with the water will increase the octane of the fuel while the water dampens detonation. A 2 liter Holley mini-fuel electric pump will be used to create enough pressure to maximize the atomization of the alcohol/water charge. I am using a computer model to work out this theory with all the variables to my particular bike. I am also customizing an SEF 98cc cylinder with a variable exhaust power valve, out of a 1984 Yamaha RZ350 two stroke engine. This valve will restrict or increase exhaust valve timing. Straight water injection misted into the phongeer exhaust,about three inches from exhaust flange, will modify the pipes sonic wave and make it more efficient. This Carburetion Theory has been successfully used on the 1932 Sterling "Silver Bullet" motorcycle. I have over 1000 highly detailed Honda Elite motor and bike building pictures on photobucket.com. Here is the link that you put in your address bar: http://s139.photobucket.com/albums/q2... ALL PHASES OF MY ELITE BUILDING IS COVERED ON THIS PHOTOBUCKET SITE. IF YOU LIKE MY VIDEOS , YOU NEED TO SEE THE PICTURES ALSO....check em' out!

I'm all for inovation, but, man that is some funny stuff he's smoking!

you can check out his "Duel carb" (note spelling) :killingme:killingme: set up HERE http://www.youtube.com/watch?v=Ms7HA9w6QyE&feature=channel_page

God I love the internet! Hours of fun!

speedpro

30th August 2009, 09:57

.

I hear Chambers and TeeZee spent the day up at Johns dyno and Chambers bike makes the same power and torque curve as the two front running CB125 4-strokes.

.

Now all that is needed is to make it handle the same and then ride it the same.

Next meeting? :done:

TZ350

30th August 2009, 10:24

Now all that is needed is to make it handle the same and then ride it the same.

Next meeting? :done:

"ride it the same" Nooooo I don't think so :laugh:

bucketracer

30th August 2009, 11:16

I'm all for inovation, but, man that is some funny stuff he's smoking!

http://www.youtube.com/watch?v=Ms7HA9w6QyE&feature=channel_page

God I love the internet! Hours of fun!

Yes SpeedDemon is worth a look. I wouldn't bellitle him, he is just another having a go and right or wrong what does it matter. His clips and comments are interesting in themselves, good on him.

TZ350

30th August 2009, 11:23

I havn't found the same / similar results as this in my experience Teezee, so I have to think the same way as Sonic V.

The correct curve for any given engine really is different to the next.

As a VERY rough guide (gulp) I suggest that such an ignition curve would be good for chambers engine, with it's "non squish" head, and "old school" expansion chamber.

Hi SS90, yes that's our thinking too. The 15deg retard RM125 ignition will most likely be better on Chambers bike as its head, pipe and porting is a good approximation of an early RM.

With John C's help we spent the whole afternoon trying different modules on my bike looking for less retard and trying to optimize the ignition.

By mix and matching different stators and black box’s the best we achieved was a retard of maybe 8 deg but have know idea of where in the curve that is. The curve was close to the original fixed ignition for HP and shape. The initial part of the power curve looked much the same but had worse over-rev. It just didn't work or we couldn't make what we had to play with work.

And to make things worse, I got all my dyno graphs on a disk and when I got home I could not open them. So I don't have a record of all that hard work.

The interesting thing was Chambers bike made much the same power and shape of power curve as the two 4-Strokes that normally run at the front. Chambers curve neatly fitted between theirs and almost exactly matched their shape. Mine was much steeper and made more power but was really peekier compared to theirs.

I run the same pipe as Chambers and could quickly fit a barrel the same as his but Dave who rides my bike occasionally likes the point and squirt clutch action. He can make it slingshot out of the corners on the clutch, this works very well on tight circuits. He prefers it to Chambers bike which is easy to ride but mine has the snap needed for quick passing or to jump forward to block an attempted passing maneuver.

To make any headway with a mapped (retarding) ignition setup for my particular motor I need to use a programmable digital ignition that I can map myself. I think my combustion chamber setup needs its own particular ignition map and to find something that will just drop in was a bit of an ask but it was worth a look.

I remember the clip you posted showing a retarding ignition in action, we need to make ourselves a setup like that, with a decent timing light that will fire from a CDI at 12,000 rpm, a degree wheel and RPM counter. With the KX and RM CDI's Our timing light turns off at about 8,000rpm.

.

speedpro

30th August 2009, 14:34

custom ignition maps are definitely the go. I spent time ages ago with Chris Sayle(Dynotech) doing run after run with careful adjustment of ignition timing between runs. I was using a YZ80 ignition that I think Darren has now. It did not retard enough for the TS100 I was running. If it was set for max power at max revs we had a handy 19.9hp. If we then tuned for peak power at lower rpm we ended up advancing the timing with the result that "peak" power dropped off. I was looking at something like 5hp increase round 5-7000rpm. This was on a motor that had a pretty respectable power curve anyway.

TZ350

30th August 2009, 14:46

A 28mm feeding a 30mm creating an ENORMOUS VELOCITY EFFECT at pinnacle of peak power.

This reminded me of a story I heard at Johns about TZ750's and the AMA's attempts at restricting their power. The story goes, that they required them to breath through a standard orifice plate. This was supposed to limit the air supply but some clever engineers/tuners figured a way of adapting a diffuser to it and changed the vena contracta effect. Eventually the TZ's made more power with the orifice plate than they did before. This story interests me because of the 24mm carb restriction and it would be interesting to see if the TZ approach could be used. I would like to know more if anyone else knows something about TZ750's and the FIM's orifice plate restrictions and how the tuners got around them.

.

F5 Dave

30th August 2009, 19:07

The problem is the carb position on a rotary disc engine. You need ~7deg taper & yes this is what I ran on my 125. You can shorten it by machining the taper starting in the carb.

TZ350

30th August 2009, 19:52

The problem is the carb position on a rotary disc engine. You need ~7deg taper & yes this is what I ran on my 125. You can shorten it by machining the taper starting in the carb.

Thanks F5. Is that ~7 converging or diverging from the carb to the port?

.

TZ350

30th August 2009, 21:04

.

70's-80's car motorcycle hot up book.

http://www.bgideas.demon.co.uk/tmanual/

Chapter-1 about power and how its measured
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch1.pdf

Chapter-2 An interesting read about carb sizes, max port flow and shape 2 and 4 stroke.
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch2.pdf

Chapter-3 combustion and the power stroke
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch3.pdf

Chapter-4 the exhaust system and expansion chamber
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch4.pdf

Chapter-5 the camshaft
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch5.pdf

Chapter-6 Ignition
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch6.pdf

Chapter-7 Supercharger or Turbo
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch7.pdf

Chapter-8 Pistons and Rods and balancing
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch8.pdf

.

SS90

31st August 2009, 04:18

that's our thinking too. The 15deg retard RM125 ignition will most likely be better on Chambers bike as its head, pipe and porting is a good approximation of an early RM.

With John C's help we spent the whole afternoon trying different modules on my bike looking for less retard and trying to optimize the ignition.

By mix and matching different stators and black box’s the best we achieved was a retard of maybe 8 deg but have know idea of where in the curve that is. The curve was close to the original fixed ignition for HP and shape. The initial part of the power curve looked much the same but had worse over-rev. It just didn't work or we couldn't make what we had to play with work.

The interesting thing was Chambers bike made much the same power and shape of power curve as the two 4-Strokes that normally run at the front. Chambers curve neatly fitted between theirs and almost exactly matched their shape. Mine was much steeper and made more power but was really peekier compared to theirs.

To make any headway with a mapped (retarding) ignition setup for my particular motor I need to use a programmable digital ignition that I can map myself. I think my combustion chamber setup needs its own particular ignition map and to find something that will just drop in was a bit of an ask but it was worth a look.

I remember the clip you posted showing a retarding ignition in action, we need to make ourselves a setup like that, with a decent timing light that will fire from a CDI at 12,000 rpm, a degree wheel and RPM counter. With the KX and RM CDI's Our timing light turns off at about 8,000rpm.

.

I think that you will develop your ignition very quickly with a degree plate. I think it would be the best value tool I have (I made it for €2)

I am not 100% sure what curve would be "ideal" with your combustion chamber (with the dished piston), but my experience with tests on ignition curves Vs head design suggests to me that what you are suggesting is correct (start at say 25 deg, advance 5 degrees more up to say 5000 RPM, then retard gradually back to maybe 14 deg at 10,000)

Essentially, I believe a "non linear" curve is in order for your particular requirements.......... but I don't know of any method of calculating a map, and it will certainly be a "test and run" situation.

An advantage you have is that your exhaust port width is limited to about 70%, and you won't suffer any localised heating of the crown that you will get with a larger bridged (or auxillery) port situation in the event that yo run "too much retard"

At work I have a mapped curve from a company that make an ignition specifically for a squish head situation, I will take a pictiure and post that tomorrow, as it may be of some help in seeing what does work in a similar situation

My experience is that on an air cooled 133cc (cast iron) engine making around 20 PS
(with a Squish head) getting the ignition map correct is good for an all over gain of 1PS (all through the range) about 2 NM and about 750 RPM more over rev...........

Non squish head on the same cylinder, I have regularly seen 2 PS gains (over a "static" set up....but of course the curve used with this head design is dramatically different to the one for the squish head!

Strangely, my experience has shown that if it is just a little out of "optimum" the power curve is much the same as a static ignition, and I have heard MANY people say that there is no gain...... not true, it is certainly worth persevering with!

Strangely, with the 125cc aluminium sleeved cylinders that I do, the gains with the ignitions are still there, but not as big as I had expected (or compared to the all cast iron cylinders)....... I put it down to the superior cooling of the aluminium compared to the all cast iron cylinders

TZ350

31st August 2009, 07:41

Thanks SS90 for your reply.

Save the stuffing around and go buy one of these http://www.ignitech.cz/english/aindex.htm

This ignition looks like what I need.

F5 Dave

31st August 2009, 09:31

Diverging. so 14 included. I think I hinted at this a little when we were still talking about rotary discs. I tried both ends of the carb but was surprised that the ugly Mikuni entry in this case wasn't the problem area. I'd made a belmouth with kneedit & a slow taper in with a blunt entry (as opposed to the airbox std fitment). A bit of silicon spray & it was easy to test it on or off.

The idea is that the velocity increases & then decreases gradually with no eddying.

Possibly more important on a reed block with it's vast area compared to the small carb.

sonic_v

31st August 2009, 12:17

The mikuni round slide 24mm carb is 28mm in diameter at the bore exit. This carb is used on some of the 60/65cc motocrossers.

speedpro

31st August 2009, 19:46

So the carb should flow enough for some reasonable horsepower. Just what are those 60/65cc motors rated to produce?

TZ350

31st August 2009, 21:16

.

Well that didn’t go so good, I have been porting the transfers and changing the roof angles of my next cylinder. I changed the mains to 29deg and the secondarys to 15deg and boost to 65deg all opening at the same time.

Timing was to be:- a Wobbly design with trans opening at 115deg ATDC for a duration of 130deg. and EX opening 86deg ATDC for a duration of 172deg, and a Wobbly pipe.

After about 40 hours work re-angling and opening up the transfers I had a pretty good-looking cylinder with the matching transfer ports opening at the exact same time. The total area of the transfer windows is now pretty close to an RGV250 cylinder.

Thomas put my cylinder on a spare bottom end and degreed it up. The transfers came out at 140deg duration, opening at 110deg ATDC and the exhaust is 194 duration opening at 83deg ATDC. Whooops, not what I was looking for at all, so what to do now.

Well I now know I can do a pretty good port job and I am able to open up the transfers to whatever time area I may need. I have a spare and still want to try the Wobbly design so I will try again with that cylinder later.

According to Bell a transfer duration of 140deg is good for 12,500 to 13,000 rpm So I guess I will finish this cylinder as a hells death old school rip snorter for Taupo, razor sharp power band, lots of clutch, should be fun.

For 12,500 rpm Bell suggests 200deg or so Ex duration. I have a good software program that works out time-area requirements for a chosen rpm and bmep, then prints out a diagram of the port window shapes required and I also have pipe designs for RGV performance pipes so it all looks good.

I have made a pretty good Perspex cylinder head so I can fine-tune the scavenging flow patterns using water and fine air bubbles like SS90 suggested.

The problem is that restrictive 24mm carb. F5 Dave has suggested a possible solution.

.

sonic_v

1st September 2009, 00:36

SS90

1st September 2009, 07:45

I have a photo of an ignition map here Teezee, but I seem unable to post it for some strange reason.......

TZ350

1st September 2009, 12:07

tz, an exh opening of 86deg after tdc gives a duration of 188deg. Assuming that this is what you meant,

There has been a lot of kart classes over the years that have used restrictive carbs. They all use the venturi principle plus the intake tract length tends to be longer than when a non restrictive carb is used.

Do you have an exhaust time area for the setup that you have been using.

Yes your right duration 188, bad mental arithmetic on my part.

Venturi principle, can you tell me more.

No time area, built on the deg/rev durations for various ports suggested by Bell.

If the TV is really crap and I want to do something even less interesting than slitting my wrists I will work out the time areas as described by Jennings, and will also take a look at Blairs work to see how it compares.

For mechanical reasions its difficult for me to lower the barrel, I will make another using the Wobbly duration specs and work through the time area calcs to dial in the port areas.

.

TZ350

1st September 2009, 12:20

I have a photo of an ignition map here Teezee, but I seem unable to post it for some strange reason.......

I would be very interested to see it if you can get it posted.

Thanks.

F5 Dave

1st September 2009, 12:40

. .

Venturi principle, can you tell me more. .

.
Um, just the principle the carb works on. with a flow rate equal on both sides of the restriction the speed of flow has to increase in the smaller section (& pressure drops as a result which is handy in a carburetor). So theoretically if you can get the velocity as high as possible for the given restriction your ultimate flow will be more which is the whole point (assuming also that good atomisation is still occurring if it is a carb).

So look at the carb. perhaps you may be better off where flow is so critical & suction is so much more, than say a 65cc mx that velocity must be much more with a 125 pulling on it. I don't know that the flow potential of a carb can be directly related for power output with extreme examples.

You may find that a 22mm carb bored to 24mm may have a smoother flow than the std 24, in fact Bell suggests that too now I think about it.

TZ350

1st September 2009, 16:15

.

Modifying the bell mouth of the GP125 carb. We think that the GP carb may have been made deliberately restrictive to meet the UK/Europe learner licence Hp laws.

Pic-1 the original carb with a concave bell mouth that looks like its designed to choke at high speeds.

Pic-2 Thomas acting up.

Pic-3 The carb is slowly rotated by the drill all day to smooth out the devcon. it takes 2-3 applications of devcon over a couple of days to get a good bellmouth shape. But when its finished we don't even have to sand it.

Pic-4 The finished modified bell mouth.

Pic-5 Shows how the carb is just pushed onto a wire brush wraped with some masking tape.

.

F5 Dave

1st September 2009, 16:54

1.
not it wasn't (a restriction maneuver), the GP125 made 13hp & was merely around when the UK legislation came in. I think I've told this story before (from reading PB in the late 80s). Suzuki UK enlisted an engineer Leon Moss to measure & restrict the GP125 so they could sell it under the 12hp rules. He came up & supplied a washer that went on top of the carb to restrict movement. Later he made money from customers wanting to derestrict their GP125s, whereby he simply hooked the washer out ready to resell to UK Suzuki. :woohoo:
Maybe they made it that way as it worked best with the sidecover so close as they only use that shape on the rotary engines? Only a (bad) guess.

You can smooth Devcon (or JBweld) with a wet finger quite nicely.

TZ350

1st September 2009, 17:38

Thanks F5, I will have to dyno two carbs back to back and see.

With the drill rotating the carb the runny devcon stayed in place while it set.

.

TZ350

1st September 2009, 17:46

.

Water testing the scavinging flow patterns.

Pic-1 the motor setup for test

Pic-2 the acrilic head

Pic-3 setting it up

Pic-4 testing

Pic-5 no idea what we are looking at.

Pic-6 the flow formed a rolling pattern twisting around like a horizontal tornado with it tail in the exhaust port.

No idea what looks good or not.

.

bucketracer

1st September 2009, 21:34

.

I have just found "Thread Tools" at the top of the page. Thread Tools drops down to "View Thread Images" These are all the images posted on the thread. Clicking on any one will take you to the post where it was posted.

23 pages of great pictures, a great way to find a post.

.

SS90

2nd September 2009, 05:16

This is pretty much a generic curve that most guys use here with a squish head Teezee, most guys set it at 25 deg idle, 17 full retard, which seems to bring the most gains.

Obviously the top curve relates to the ignition timing (just to save confusion)

TZ350

2nd September 2009, 19:50

Thanks SS90. it looks more like what I need.

We have got an acrylic head and air/water set. I expect with a bit of experimentation we will be able to start getting some worthwhile info from it.

I over cut the transfers on my new barrel, they are now opening 110deg ATDC I was trying for 116. But it may not be such a bad thing as I can now devcon them back to 116 or less and slowly open them up again looking for the blow-down sweet spot.

Last time I used Bells duration recommendations to plan my ports this time I will go to the extra effort and use time area's to plan them. I know I can re-angle them and increase their area so should be able to get any time/area required. The main port is quite wide and I could put a divider in the middle for extra control of the transfer stream.

.

TZ350

2nd September 2009, 22:19

.

A quick look at my inlet port using Angle/Area from Jennings page 81-82
http://www.vintagesleds.com/library/manuals/misc/Two-stroke%20Tuner%27s%20Handbook.pdf

Angle/Area is not Port/Time/Area that's something else.

Finding the mean area for the Port/Time/Area calculation for exhaust and transfers is relativly straight forward but I used Angle/Area for the inlet because I am unsure of how to calculate the mean area of the rotary valve inlet port.

Angle/Area = Capacity X PortArea/Duration

For my GP125 with an inlet port area of 2.6cm3 and opens 145BTDC closes 85ATDC, Inlet Duration 230deg.

Angle/Area = 125 X 2.6/145 = 9.7

According to Jennings chart a rotary valve Angle/Area of 9.7 is ideal for 8,500 rpm

So using the quick and dirty Angle/Area I can see that the 24mm carb is a real problem.

To get the Angle/Area required for 10,500rpm I have to increase the Area of the Port (and carb) and/or the Duration which is pretty much at its limit.

I am taking a careful look at how to design a venture for maximum flow.

.

SS90

3rd September 2009, 05:34

.

Water testing the scavinging flow patterns.

Pic-1 the motor setup for test

Pic-2 the acrilic head

Pic-3 setting it up

Pic-4 testing

Pic-6 the flow formed rolling pattern twisting around like a tornado with it tail in the exhaust port.

.

This is actually a little brave of me, but from my screen it looks like you have a large degree of shortcircuiting particularly from the rear transfer port (boost port), but also from the righthand set of transfers (looking from the top)

I recommend dividing the picture you posted into 4 sections, and enlarge it as much as you can, this is what I have done and I am getting a good picture.

Basically, it isn't the worst one in the world, all things considered it's "OK", but (in my opinion) you are getting short circuiting in two places, and I believe the cause is the same.

I believe the rear transfer (boost) port is causing problems due to it's proximity to the secondary transfers.

Here is what I would do.

Just for a test (easy one) using RTV (or hot melt glue), or what ever really, plug the rear transfer/boost port completely, and essentially remove it from the equation (just for the purpose of seeing if it is indeed causing the problem)

If the remaining transfer ports "even up" their patterns, then it is logical to say that the rear port is the problem, and as such, either a new angle will need to be found, OR, (maybe) remove the walls between the rear port and the secondaries, and angle the new "single" port about, 70 deg up into the head.

Sort if a "collide stream port effect" (this is only a theory, but I have been thinking about it for a few months now, and the idea keeps coming back)

Unfortunately, I know of no other cylinder with a set up such as that (with the secondary transfers so close to the rear port), so I can't compare it to something "proven"

With a little logic though, as we have talked before, perhaps (like you mentioned again in a recent post) a divider in the transfers MAY help a bit as well, but like I say, these cylinders are a bit of an "orphan", so to a certain degree, you may well be heading into uncharted territory as far as improving this area.

Also, an important thing to watch is try to get the air pressure VERY VERY low, and watch as the smallest bubbles start coming through the system..............

Obviously you need to watch with a variety of pressures, but the low pressure gives you a real insight to aspects a book can never do!

Basically in my opinion Teezee, from your pictures, the left set of transfers looks alright, the rest looks like it is short circuiting (to me anyway)

TZ350

3rd September 2009, 06:46

.

Thank you for your insights, I will try them. We will get better with practice at making bubbles and post better pictures.

.

bucketracer

3rd September 2009, 20:41

Great looking bubbles your making there TZ

TZ350

3rd September 2009, 20:43

Do you have an exhaust time area for the setup that you have been using.

Jennings page 81-82 http://www.vintagesleds.com/library/manuals/misc/Two-stroke%20Tuner%27s%20Handbook.pdf

Port/Time/Area for the Exhaust Port 0.00018 – 0.00019 Cm2 x Sec / Cm3

Port/Time/Area is found by dividing Cylinder Volume into the Mean Port Area and multiplied by Time.

Mean Port Area is the area of the port uncovered by the piston when the crank is moved half way between port opening and BDC.

For my Suzuki GP125 exhaust port at 10,500Rpm Ex opens 83deg ATDC 71% bore dia 194deg duration, with a mean exhaust port area of 7.0cm2.

Step-1 Divide Cylinder Volume into the Mean Port Area.

Mean Port Area / Cylinder Volume

7.0cm2 / 125cc

7/125 = 0.056

0.056 cm2/cm3

Step-2 Time

Time = Duration / Rpm x 6

Time = 194 / 10,500 x 6

Time = 194 / 63,000

Time = 0.0031 sec

Step-3 find Port/Time/Area

cm2/cm3 x Time

0.056 x 0.0031 = 0.00017

0.00017 sec cm2/cm3

0.00017 is a little less than the 0.00018 – 0.00019 listed in Jennings so more exhaust port area or duration is required.

Tuned length for the pipe is 970mm measured from the GP125's piston to the end of the convergent cone.

Pipe dimensions Suzuki RM125 B/C page 82 Bell. http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf

.

sonic_v

4th September 2009, 08:01

0.00017 is spot on for an engine were you require a good spread of power. Basically, you have a 25hp exhaust port there. (for an air cooled engine) The fact that you are five short indicates that your problems are elsewere. Pulling the engine speed down via a longer exhaust system is likely to find some of this power plus your intake work should find most of the rest. I have found it possible to make excellent power with exh time/area as low as 0.00016 plus a nice spread of power.

Working at 10,500rpm will result in a considerable increase in bmep with the result that your engine should respond better to your retarding ignition.

As for venturi in your intake, I would suggest a taper from the choke of the carb out to 30mm should be adequate, keeping included angle below 14degrees as has been mentioned elsewere. I suspect that once the intake is flowing better, that you will be able to close the disc valve earlier. This is the area that needs looked at before thinking of a new pipe.

Just out of interest, what diameter is your exhaust port?

PS the work you have done on your carb might well make a big improvement!

bucketracer

4th September 2009, 20:34

Port/Time/Area for the Exhaust Port 0.00018 – 0.00019 Cm2 x Sec / Cm3

.

TZ you have made a mistake the time you quote is for a rotary valve inlet not exhaust.

The correct time areas are.

Port/Time/Area for the Piston inlet Port 0.00014 – 0.00016 Cm2 x Sec / Cm3

Port/Time/Area for the Transfer Port 0.00008 – 0.00010 Cm2 x Sec / Cm3

Port/Time/Area for the Exhaust Port 0.00014 – 0.00015 Cm2 x Sec / Cm3

Port/Time/Area for the Rotary Valve Inlet 0.00018 – 0.00019 Cm2 x Sec / Cm3

So your time of 0.00017 is possibly better suited to 11,000 than 10,500.

sonic_v

4th September 2009, 23:00

SS90

5th September 2009, 04:29

Well spotted there BucketRacer. Fortunately I am working from what modern production two-stroke racing bikes (honda rs125, tz250, aprilia rs125) actually measure, which in standard trim is often or not 18-19.

Hence this is the reason I like to work in the 16-17 range for tuned motocrosser/road engines for track racing.

Realising that F5Dave was quite right with his warnings regarding port timings etc (i.e "throwing them around), time area's for an Rs125,Tz250 etc are quite different in requirements.

By that I mean, 18-19 is quite high for an air cooled disc valve 125cc two stroke, (running a 24mm carb)

Where as the examples you mention are all Crankcase induction water cooled two strokes (the Yamaha and Aprilia have power valves as well) with carbs a up around 40mm.

And as you well know, 125GP bikes (the "production" ones anyway) only get ridden from around 9,000 to 13,000 RPM (roughly, let's not split hairs!)

And with a wee carb like Teezee has by 9,000RPM it's pretty much all over.

I think Teezee is trying to find a figure suitable for his piddly little carb.

That's how I see it, I may be wrong!

I am interested in the results with the carb bell mouth changes, I have tested dozens of Bell mouth types/designs, but never found anything that made a real difference (on low BMP stuff like this anyway)

With higher power stuff (Rs125's TZ250's) I have noticed gains/losses as far as that is concerned.

sonic_v

5th September 2009, 13:10

Realising that F5Dave was quite right with his warnings regarding port timings etc (i.e "throwing them around), time area's for an Rs125,Tz250 etc are quite different in requirements.

By that I mean, 18-19 is quite high for an air cooled disc valve 125cc two stroke, (running a 24mm carb)

Where as the examples you mention are all Crankcase induction water cooled two strokes (the Yamaha and Aprilia have power valves as well) with carbs a up around 40mm.

And as you well know, 125GP bikes (the "production" ones anyway) only get ridden from around 9,000 to 13,000 RPM (roughly, let's not split hairs!)

And with a wee carb like Teezee has by 9,000RPM it's pretty much all over.

I think Teezee is trying to find a figure suitable for his piddly little carb.

That's how I see it, I may be wrong!

I am interested in the results with the carb bell mouth changes, I have tested dozens of Bell mouth types/designs, but never found anything that made a real difference (on low BMP stuff like this anyway)

With higher power stuff (Rs125's TZ250's) I have noticed gains/losses as far as that is concerned.

Indeed 18-19 for exhaust time/area is too high for an aircooled engine and hence the reason that I have suggested a value of 16-17, which taking the mean values results in 11% less time area.

((18.5 - 16.5) / 18.5) * 100% = 11%

Also, to take into account that this is a tuned air cooled production road engine with a 24mm carb, I have suggested that peak power speed of 10,500 rpm would be about right.

If we take a production rs125 aprilia (disc valved intake ) as an example with a peak power speed of 12,500 rpm this represents a reduction in engine speed by 16%.

((12500 - 10500) / 12500) * 100% = 16%

In total these two measures represent a potential mass air flow reduction in the region of 25%.

On the subject of the 24mm carb, a correctly designed diffuser could easily make the intake flow at least as well as a 26mm straight through carb. This is easily sufficient for 25hp.

As for "low bmep stuff like this" I would suggest that this engine has the potential to give a bmep of 9.5 bar at peak torque which is not exactly low bmep.

An engine set up as above will pull strongly from 7500 rpm through to 11000rpm.

Just out of interest TZ, do you have aspirations HP wise for this engine.

TZ350

5th September 2009, 20:29

SS90 is right my thinking and planning now centers around what is possible with a 24mm carb.

My exhaust port dia at the flange is 36mm and mid 20's for rwhp would be good, I feel I have the cooling to handle it.

I have been reading up about designing venture tubes as flow measuring instruments because there is quite a bit of information about diffuser angles.

So far I have read that given a convergent angle of 10.5deg into the front of the venture then a diffuser of 5-7deg has a lower net pressure loss than a 14-15deg diffuser.

And then there are the other things like:-

4-Strokes like a convergent inlet port. Other rotary valve arrangements I have seen are size for size and one or two convergent.

There is also the thought that pressure waves like convergent and sound waves like divergent diffusers.

When I set up MOTOR with a 24mm carb and 30mm port it predicted a power increase throughout the rev range.

I tried this once but was not very impressed.

So I am not sure what to make of any of this yet.

Its easy to imagine the carb as the throat of the venture.

.

SS90

5th September 2009, 21:30

Also, to take into account that this is a tuned air cooled production road engine with a 24mm carb, I have suggested that peak power speed of 10,500 rpm would be about right.

((12500 - 10500) / 12500) * 100% = 16%

In total these two measures represent a potential mass air flow reduction in the region of 25%.

On the subject of the 24mm carb, a correctly designed diffuser could easily make the intake flow at least as well as a 26mm straight through carb. This is easily sufficient for 25hp.

As for "low bmep stuff like this" I would suggest that this engine has the potential to give a bmep of 9.5 bar at peak torque which is not exactly low bmep.

An engine set up as above will pull strongly from 7500 rpm through to 11000rpm.

Just out of interest TZ, do you have aspirations HP wise for this engine.

That's quite interesting sonic_v.

personally, I have never seen more that 21PS from an engine with a 24mm carb, regardless of bell mouth/venturi design.

Two years ago I was lucky enough to work with someone who uses MOTA for a living, and was quickly shown that it is a tool that requires years of experience.

With an experienced operator on a 125cc aircoled engine the result was always 21PS, and when we built that engine, it was pretty much 20PS.

Previously (when I had tried to use the program) I, like Teezee and Thomas has seen 28PS as a prediction.

I simply didn't have the experience.

I too had thought that 24PS or so was possible, but I don't know of anyone who has built a 125cc air cooled disc valve engine with a 24mm carb that has more than 20PS.

OK, I don't knnow everyone in the world, but the limitations of that carb size, particularly operating over 9,000 RPM is quite something to overcome.

I will see if I can find a copy of the dyno runs.

My experience with air cooled 125cc engines to get around the BMEP you are suggesting requires a carb size in the area of 28 to 30MM.

Have you found different?

TZ350

5th September 2009, 21:47

Yes you don't want to take MOTA's predictions of ultimate power to seriously but it is a good friend that's qualified to give me an informed opinion of what the likely outcome will be of any changes I make.

MOTOA's certainly been a whole lot better at it than my mates at the pub have been. :apint:

Now that I have a base line run I could adjust MOTO to reflect the torque curve and then it will more accurately show the power output and any changes I make.

The big overoptimistic HP numbers are great for psyching the opposition though.

.

sonic_v

5th September 2009, 22:28

TZ I would agree with the shallower angles you are quoting for optimum pressure recovery. Really it is all a matter of what is an acceptable intake tract length as the shallower angles will increase it.

I do not know if you use a fairing and thus have a packaging problem. Personally, I have cut a hole in the fairing before now that the bell mouth just peeped out of. No problems at all.

Your carb looks a lot better than the original standard version, and thus I would concentrate on the downstream side. i.e diffuser.

As for Mota. Do you still have to estimate the exhaust gas temperature. It is a long time since I have used it. Can you model a diffuser in the intake or is it modelled as a step. i.e A jump from 24mm to 30mm?

SS90

5th September 2009, 22:35

As for Mota. Do you still have to estimate the exhaust gas temperature. It is a long time since I have used it. Can you model a diffuser in the intake or is it modelled as a step. i.e A jump from 24mm to 30mm?

That's interesting. I was quite amazed at the importance of how you represent the intake with Mota, it seems to be where many people fall flat.

SS90

5th September 2009, 22:38

I can't claim responsibility for this engine, but (so far) the highest power I have seen from this capacity with a 24mm Carb is this series of runs.

The red line was a different exhaust.

sonic_v

5th September 2009, 22:47

That's interesting. I was quite amazed at the importance of how you represent the intake with Mota, it seems to be where many people fall flat.

Sorry, you have lost me there. Could you elaborate more!

The graph of the engine power, some details on it would be interesting.

gav

5th September 2009, 23:55

Heres what the rules say about using a 24mm carb for your F4 bike.

F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm carburettor,

Typically vague and ambiguous, but if you modify the inlet so it flows like a 26mm (or bigger) carb, is the carb still the equivalent to a single 24mm carb? Its not, is it? Therefore would it be legal to run that modified carb? :whistle:

speedpro

6th September 2009, 00:29

gav

6th September 2009, 06:31

Yeah, and the motor is making power like a 150cc 2-stroke so it's not legal for bucket racing anyway, using the same logic.

The rule you quote refers only to a dimension so therefore the legality, or not, must be determined purely on that dimension. Hardly vague or ambiguous.
Well, Im sure youre aware that the rules state nothing about the allowed power output, so not too sure how that applies to anything?
The rules obviously allow for a multi cylinder two stroke to be eligible, so instead of saying a F4 bike is restricted to a 24mm carb, they use a term "equivalent to a single 24mm carb". Does a 24mm flat slide flow the same as a 24mm CV carb? Are all 24mm carbs the same? Its the use of the word "equivalent" that allows interpretation, doesnt it?

bucketracer

6th September 2009, 09:25

.

The size of a carburetor is measured at the venture choke that's right inside where the slide is, not at either end which is bigger and not all carbs flow the same as for some carbs their ultimate flow numbers are secondary to how they drive on the street.

.

speedpro

6th September 2009, 10:12

F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm carburettor,

This rule is written with the person in mind who would fit two carbs to an engine. It's a bit of bad luck for the Suzuki 125 twins but they seem to work OK with just one 24mm carb anyway. The rule was introduced at an MNZ conference at Taupo years and years ago and so far nobody has worked out a way round it.

If the rule read that "a F4 bike is restricted to a 24mm carb", then it could be interpreted that the max carb size is 24mm but you could run more than one.

There is no restriction on the carb type and in fact it is not mentioned anywhere. Neither is it mentioned anywhere about restrictions to mods you can do.

I do see your point about the word equivalent. In this case it refers to the size not the performance and that is how everybody has interpreted it so far. I'd like to see someone arrive at the track with a 28mm carb fitted and flow bench analysis to show that their 28mm carb flow wise is "equivalent" to some 24mm carb. The obvious question would be "why don't you fit the 24mm carb?"

TZ350

6th September 2009, 13:47

My experience with air cooled 125cc engines to get around the BMEP you are suggesting requires a carb size in the area of 28 to 30MM.

Have you found different?

Thanks for the dyno run.

I worked the time area figures at 12,000rpm for various carbs and it came out at 32mm for an inlet timing of 145/55 which is the std timing for a GP125 and about 28-30 for later closing.

.

bucketracer

6th September 2009, 14:51

I can't claim responsibility for this engine, but (so far) the highest power I have seen from this capacity with a 24mm Carb is this series of runs.

That curve looks much like TZ's but at lower and more sensible rev's.

TZ350

6th September 2009, 14:54

Your carb looks a lot better than the original standard version, and thus I would concentrate on the downstream side. i.e diffuser.

As for Mota. Do you still have to estimate the exhaust gas temperature. It is a long time since I have used it. Can you model a diffuser in the intake or is it modelled as a step. i.e A jump from 24mm to 30mm?

Yes you still have to estimate EGT and need to resort to a bit of trickery to model a tube inlet tract.

http://www.bevenyoung.com.au/motaman.htm#_Toc504313324

MOTA inlet configuration for rotary valves. As I remember it, MOTA treats the carb as a venture tube, it asks whether the inlet is bell mouth or not, size, length to choke, dia of choke (carb), length to exit (flange) and dia. Then the dia of the inlet tract (carb flange), and length of the inlet tract to the disk face.

MOTA assumes a pie slice configuration of the port window and asks the dia to the bottom radius, the dia to the top radius, port arc and corner radiuses. My GP has a round port not a pie slice port so I made the corner radiuses 12mm (for a 24mm port).

Whenever I reduce the radiuses to 4mm and hence a bigger port, MOTA predicts a power gain. This would be encouraging if MOTA knows that the inlet tract was changed from a tube to a divergent cone.

In first setting up MOTA you need to know the torque curve as well as the other data so you can adjust MOTA to fit the curve then it will more accurately predict changes to the engines configuration.

When Thomas first setup the base files for our GP125’s we only had the max hp, torque and revs of a std GP125 but no graph. Now that we have a good torque/revs graph we can dial in MOTA better.

We will update the file and then explore inlet tract changes and see what MOTA comes up with.

.

F5 Dave

6th September 2009, 19:39

F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm carburettor,

This rule is written with the person in mind who would fit two carbs to an engine. It's a bit of bad luck for the Suzuki 125 twins but they seem to work OK with just one 24mm carb anyway. The rule was introduced at an MNZ conference at Taupo years and years ago and so far nobody has worked out a way round it.

. . . Well there is a bit of a way around it :cool:but it isn't really worth the effort.

In general it is a good rule in that it is simple. I do wonder whether 26 would have been more fair, but there you go.

Nice inlet tract TZ. Lets see you fit that to a race bike. I have seen a GP run with a carb on the end of a long tube, but I can't imagine the throttle response wouldn't be cacked up,.

bucketracer

6th September 2009, 19:43

Nice inlet tract TZ. Lets see you fit that to a race bike. I have seen a GP run with a carb on the end of a long tube, but I can't imagine the throttle response wouldn't be cacked up,.

I think he is going to put a wheel on it and go side car racing.

.

bucketracer

7th September 2009, 20:21

.

Hot Rods web page, Search by application, part type, dimensions or model to find the parts you need.

Put in the rods center to center distance and find the rod you need for your bucket. Great heavy duty rods for 4-strokes too.

http://www.hotrodsproducts.com/index.cfm?fuseaction=cProducts.search

.

Bert

7th September 2009, 22:00

TZ350

8th September 2009, 15:18

.

Now that we are getting into carb setup and tuning this might be helpfull.

Carb Tuning by Eric Gorr:- http://www.cyclewerksracing.com/Carb%20Tuuning.htm

.

TZ350

8th September 2009, 20:29

.

Ignition system number three. Had to make a small mounting adapter ring for it. With these KX80 ignitions the stator needs packing up 8mm so I used a piece of 10mm plate and stepped the stator into the ring 2mm and it all worked out very well.

Setup like it is the trigger coil fits neatly into a recess in the crankcase and the original ignition timing marks still line up, so there should be no problems with getting it running, just need to dial it in on the dyno. I like it, it all fits in very nicely.

It is an older KX80 (I think) ignition I got from F5 Dave, I am unsure how much retard or what its curve is if any. I think it has some retard but it was not enough for F5 so hopefully it might be the 5-7 at 10,500rpm I need and not 15deg like the RM one.

Whatever, it has a trigger coil so if it does not work out I will be able to try my JaCar programmable ignition again and if there is no joy there I will get one of those digital units that K14 told us about.

The blue line that drops off at 11200 is the 17deg BTDC fixed ignition. The green line is the RM ignition with 15deg retard (aprox). It is setup to advanced between 7500 and 10500 and is losing power but retards to the right point about 11000 for a very use-full 500-750 rpm over rev. With an ignition that has less retard or a programmable ignition I think I can have the best of both the blue and green lines.

.

TZ350

9th September 2009, 20:12

.

A rotary valve cover that has been opened out at an angle of 6deg I plan on boring the carb from just behind the 24mm venture at an angle of 6deg and carry it on all the way to the rotary valve port in one continuous taper.

Pic-1 shows the plan.
Pic-2 the standard cover
Pic-3 the modified cover
Pic-4 inside of both covers
Pic-5 outside of both covers

Absolutely no idea if this will work but it sure opens the inlet tract up.

.

sonic_v

9th September 2009, 23:58

What equivalent diameter have you went for at the port?

Is your intake length being lengthened and if so by how much?

jasonu

10th September 2009, 13:12

'D' bored 28mm flatside carbs from the older RG250 and RG400's work just fine. I got more than 22hp out of my KE/RG100 with a nice mid range too

jasonu

10th September 2009, 13:17

Pity about the cranks and clutches

C'mon Green we all know TF100 cranka are bullit proof especially at Taupo...

TZ350

11th September 2009, 17:18

.

What equivalent diameter have you went for at the port?

Is your intake length being lengthened and if so by how much?

“equivalent diameter” = 32mm…..“intake length” = std GP125 at 90mm from bell mouth entry to disk face.

The port window is 50deg wide like an RG500 the std GP is 40deg wide. Inlet opens 145deg BTDC and closes 85deg ATDC. I figure if it was 32mm straight through then I could close the inlet timing of a std GP125 which is 145/55 and still have good port/time/area.

The inlet tract starts with a bell mouth. The first part of the inlet tract converges from 26 to 24mm at the needle jet and is 15mm long. The second part diverges from 24 to 32mm from the needle jet to the rotary valve face and is 75mm long.

The overall length of the inlet tract to the rotary valve is 90mm and past the rotary valve the inlet tract diverges bell mouth like into the crankcase.

I have a new OKO 24mm flat slide carb. It is bored 24mm parallel right through. There is plenty of metal to turn a 6 deg taper starting from just behind the 24mm choke at the needle jet diverging out to 28mm at the flange.

Then the rubber manifold and the rest of the inlet tract can then be ported, diverging out from the 28mm manifold rubber to 32mm at the rotary valve face.

.

TZ350

11th September 2009, 20:02

.

Flow tested some carbs today. Thomas made up a manometer, which proved to be very effective at measuring flow through the carburetors. We found that the shape of the standard GP125 carbs concave bell mouth is not the restriction I thought it was.

Thomas made the manometer from some clear tube an old tape measure and some din rail and filled it with anti freeze and it worked a treat. He's a clever fellow is Thomas.

Tests show that the modified 24mm carb did not flow much if any more than the standard carb. The various obstructions in the carb like the size of pilot jet nozzle and idle screw made more difference than the modified bell mouth did.

The 24mm OKO flat slide flowed as much as an ordinary 26mm round slide carb.

Pic-1 the setup, first time it was switched on the vacuum cleaner sucked all the anti-freeze out of the manometer. Thomas then fitted a restrictive washer with a 22mm hole into the white tube.

Pic-2 shows how the restriction of the carb allows the vacuum to suck one side up the tube. The more restrictive the carb the greater the imbalance is and you measure the distance between the high and low side.

Pic-3 Of the three carbs being tested. The OKO flat slide was the best by far.

Pic-4 Measuring the difference between the columns. The greater the distance the more restrictive the carb.

Pic-5 Obstructions in the carbs that made a real difference to how they flowed.

Pic-6 Thomas also turned up a standard 24mm orifice so future measurements can be compared to a known standard.

The needle, neddle jet and the sharp edges around where the slide goes are really disruptive to air flow. The old English TT GP racing carb had the needle out of the throat and in a chamber on the side of the carb so that there was no obstructions in the air stream.

.

sonic_v

12th September 2009, 02:12

If you used a settling box between the carb and vacuum source it would allow you to test the whole inlet system as one. The rotary valve cover could be bolted directly to the box with the various carbs and rubbers also attached. You would then test the inlet systems at the same selected box vacuum. Essentialy the box is your crankcase.

Downstream of the box you can use a oriface plate machined to the british standard for oriface plates. By measuring the pressure each side of oriface plate you can calculate the mass flow. This will allow you to put some numbers on the various inlets i.e x flows 10 % better than y etc. You can even test for varying disc openings.

TZ350

12th September 2009, 17:21

.

Thanks for the ideas Sonic.

.

bucketracer

12th September 2009, 17:56

More flow does not always mean more useful HP.

TZ350

12th September 2009, 17:59

More flow does not always mean more useful HP.

Yes I know bucketracer. :( I could get more peak hp but less total area under the torque curve due to poor inlet tract shape and gas velocity.

I have been playing some more with Thomas’s flow rig. And all the while there was a tape playing in my head reminding me that big flow test numbers do not necessarily mean improved hp, but I can't resist.

Inside carbs where the slide goes there is some sharp edges that I think must be very disruptive to airflow.

On my OKO carb I turned a 6 deg taper from the rear of the carb to just before the needle jet and radiused the sharp edges around the slide, now when I push my finger through the carb the edges feel smooth and less disruptive.

The carb is still 24mm at the choke but flows significantly better.

But because I changed two things at once I cant say for sure which contributes the most. I will experiment with just radiusing the sharp edges in another carb later to see.

Pic-1 I figure that if just these sharp edges were shaped then the net flow through the carb should be improved without a down side on the torque curve, its the diverging taper bit I am not sure about as most anything you read (4-stroke) has the inlet tract converging there is very little about 2-stroke inlet tracts and even less about rotary valve inlets.

.

edgefinder

13th September 2009, 05:08

k14

13th September 2009, 06:09

Good read, just registered and up to page 7

Before I get to page 89 and forget, back in 1976 or 77 we went to a 125 national mx and Marty Smiths bike had a copper cylinder head. It looked like it was all machined not cast. It was vary humid 100 deg F day and i'm sure it helped, psyched them out too.

Can you guys only use parts from bikes legal for the class? I'm looking at an old sachs 125 6b radial head thats got loads of fins, could easily be welded up and cut for another motor. Some were sold as street legal bikes over here.

Luther
This is for a class called buckets. Max 2 stroke capacity is 100cc water cooled or 125cc air cooled (max 24mm carb too), 4 stroke is 150cc max. After that pretty much the only rules are no competition engine parts allowed (so no MX or GP bike engine parts). There are a few exceptions but those are the basic rules. So most of the bikes are commuter type bikes highly modified. Chassis is totally free so you can do whatever you want there. It's a great starting class, you can have a bike for around $300 and go racing!

TZ350

13th September 2009, 09:20

Good read, just registered and up to page 7

Before I get to page 89 and forget, back in 1976 or 77 we went to a 125 national mx and Marty Smiths bike had a copper cylinder head. It looked like it was all machined not cast. It was vary humid 100 deg F day and i'm sure it helped, psyched them out too.

Luther

Hi Luther, glad you like the thread. Near the top off the page is a tool bar "Thread Tools" which opens to "View All Thread Images". A quick way to see all the pictures.

Thanks for the tip about Marty Smiths copper head, I found picks of the internals of one of Martys water cooled engines here http://www.mxworksbike.com/Honda%20works%20parts.htm I would love a pic of the copper head if you ever come across one.

Our engines/gearboxes are restricted to road legal stuff except ignition/carb/piston but you can hand make anything you like for the engine/gearbox. And anything goes for the rolling chasis. There are a few other class restrictions, 125 2-stroke must be air cooled and 24mm carb. And a class formula 100cc 4-strokes run with 50cc 2-strokes. 150cc 4-stroke run with 125cc 2-stroke.

.

TZ350

13th September 2009, 09:43

.

You have just got to go and look at these goodies. a works 2-stroke magnesium cylinder:- http://www.mxworksbike.com/Yamaha%20works%20parts.htm

.

F5 Dave

13th September 2009, 10:30

yeah if the carb is just firing unatomised fuel at the engine there will not be efficient running. but i'd assume it would be a given with such high velocity that better flow would only be of benefit. good idea with test jig.

the shroud many 2 strokes have over the needle area on larger carbs help atomisation, but the velocity in smaller carb prob doesn't worry it as much.

TZ350

14th September 2009, 19:14

But because I changed two things at once I cant say for sure which contributes the most. I will experiment with just radiusing the sharp edges in another carb later to see.

Tried smoothing the sharp edges ( I tried this twice with two different carbs) and measuring the difference to the flow through the carb. There was a definite and measurable difference of about 8-10%, not as good as I hoped but worth having.

.

TZ350

14th September 2009, 19:25

A collection of links from the last ten pages more links are on page 80

Expansion Chamber Design According to Blair:-
http://members.bellatlantic.net/~vze2p5sj/modelengines/expcham.htm

Another interesting pipe design program:- http://www.mh-aerotools.de/airfoils/javapipe_en.htm

One of the things I like about the software from porting-programs.com 2 Stroke porting software for the enthusiast http://www.porting-programs.com/ is that it makes it very easy to get the true total and mean port areas of the transfers.

This http://www.geocities.com/a57ngel/moto/CDI.html talks about repairing/modifying a KDX CDI's retard curve, there is also a schematic.

We see that the flow bends upwards and forward towards the exhaust port as the cycle proceeds and the piston rises to shut the port. Abstract taken from http://www.lortim.demon.co.uk/vsih/pistons.htm

Hot Rods web page, Search by application, part type, dimensions or model to find the parts you need.
Put in the rods center to center distance and find the rod you need for your bucket. Great heavy duty rods for 4-strokes too.
http://www.hotrodsproducts.com/index.cfm?fuseaction=cProducts.search
70's-80's car motorcycle hot up book.

http://www.bgideas.demon.co.uk/tmanual/

Chapter-1 about power and how its measured
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch1.pdf

Chapter-2 An interesting read about carb sizes, max port flow and shape 2 and 4 stroke.
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch2.pdf

Chapter-3 combustion and the power stroke
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch3.pdf

Chapter-4 the exhaust system and expansion chamber
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch4.pdf

Chapter-5 the camshaft
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch5.pdf

Chapter-6 Ignition
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch6.pdf

Chapter-7 Supercharger or Turbo
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch7.pdf

Chapter-8 Pistons and Rods and balancing
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch8.pdf

Save the stuffing around and go buy one of these digital, programmable ignitions
http://www.ignitech.cz/english/aindex.htm

The best bell mouths are those that are short and fat!
http://www.profblairandassociates.com/pdfs/RET_Bellmouth_Sept.pdf

4-Stroke valve spring design
http://www.profblairandassociates.com/pdfs/RET036_Blair.pdf

Pneumatic vs Steel valve Springs
http://www.profblairandassociates.com/pdfs/Steel_Springs_Vs_Gas.pdf

Acceleration testing of a 2-Stroke
http://www.2stroke-tuning.nl/media/artikelen/2takt_dyno_blair.pdf

Tuning a cart engine exhaust
http://www.bkarting.com/tech-docs/expchmbr.pdf

Advanced 2-Stroke tuned exhaust design
http://www.freewebs.com/jsu_tiedostot/pdf/2003exhaust.pdf

Intake bell mouth design
http://www.profblairandassociates.com/pdfs/RET_Bellmouth_Sept.pdf

Designing a race 4-Stroke
http://epubl.ltu.se/1402-1617/2006/099/LTU-EX-06099-SE.pdf

Small 2-Stroke direct injection retro fit.
http://www.envirofit.org/media_docs/publications/SAE%20SETC%20Design%20of%20a%20Direct%20Injection% 20Retrofit%20Kit%20for%20Small.pdf

A look at the books ava for designing and testing engines
http://store.sae.org/catalog/powertrain.pdf

A whole bunch of articles from Gordon Blair in Race Engine Design mostly 4-Stroke, so more for the FXR boys.
http://www.profblairandassociates.com/RET_Articles.html

Another from G Blair on 2-stroke direct injection. http://www.etsmtl.ca/zone2/clubs/quiets/ets_ic_design_paper_2009.pdf

Anyone can open a free account with Scribed where they can download "Tuning for Speed" by Phill Irving. http://www.scribd.com/doc/15392252/Tuning-for-Speed-P-E-Irving-1965-Tuning-Racing-Motorcycle-Engines

An explanation of the expansion chamber design process proposed by Gordon Blair.
http://members.bellatlantic.net/~vze2p5sj/modelengines/expcham.htm

A very through treatment of 4-stroke engine design fundamentals by Gordon Blair. http://www.profblairandassociates.com/pdfs/Back_to_basics.pdf

I was particularly impressed by how they measured port angles.
www.kartweb.com/TechArt/2Stroke/chapter2.doc

Haven't found Bell yet but came across this on ignitions. yes its cars and 4-stroke but informative nevertheless.
http://www.max-boost.co.uk/max-boost/ignition_deeper.htm

We have been having some success with developing a data logging system for our buckets. We use a new to the market Track Day system http://www.xtracing.com/en/gpxpro/features.php and have made a small instrumentation interface so we can log CHT and EGT temperatures.

Now that we are getting into carb setup and tuning this might be helpful.
Carb Tuning by Eric Gorr:- http://www.cyclewerksracing.com/Carb%20Tuuning.htm

Port/Time/Area Jennings page 81-82 http://www.vintagesleds.com/library/manuals/misc/Two-stroke%20Tuner%27s%20Handbook.pdf

Pipe dimensions Suzuki RM125 B/C page 82 Bell. http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf

Lots of interesting Vid Clips of DIOSpeedDemon porting and developing his motor the Gordon Blair way.
http://www.youtube.com/user/DIOSpeedDemon

.

k14

14th September 2009, 20:31

Tried smoothing the sharp edges ( I tried this twice with two different carbs) and measuring the difference to the flow through the carb. There was a definite and measurable difference of about 8-10%, not as good as I hoped but worth having.

.
I would have thought 8-10% is a huge amount considering the relatively small changes you made to the carb. Good work. Interesting seeing the experimentation you are doing!

TZ350

14th September 2009, 22:38

I would have thought 8-10% is a huge amount considering the relatively small changes you made to the carb. Good work. Interesting seeing the experimentation you are doing!

8-10% reduction in vacuum, does that mean 8-10% increase in mass flow? just not sure what it means. For mass flow I would have to measure it the way Sonic-V suggests, or experiment on a dyno, but its a very interesting result for such a little change.

.

bucketracer

15th September 2009, 21:51

.

Register and download for free Motorcycle repair manuals. http://www.repairmanualclub.com/motomanuals/index.php

.

bucketracer

16th September 2009, 20:35

.

Malaysian motorcycle drag racing:- http://www.youtube.com/watch?v=J2lK-CaoTQI&feature=related

See these boys launch:- http://www.youtube.com/watch?v=yuMX_5mSTwE&NR=1

Some of them, like Thomas must know a thing or two about 2-stroke engine tuning.

.

diesel pig

16th September 2009, 21:49

bucketracer

16th September 2009, 22:49

.

Der geht doch ziemlich mager oder? http://www.youtube.com/watch?v=jkLfJ1-Pw1c&feature=related

.

bucketracer

17th September 2009, 07:47

If you could start this quick with your bucket:- http://www.youtube.com/watch?v=yuMX_5mSTwE&NR=1

TZ350

20th September 2009, 21:58

.

Rebored the cylinder and chamfered the ports before gluing up the transfer porting mistakes, actually over cutting the transfers and then gluing them back up turns out to be a real easy way to get a smooth symmetrical port. I had mistakenly cut the ports so they opened 110deg ATDC when I really wanted 116.

Now I have a really good experimental barrel. So I degreed up the motor again at 116 ATDC and measured how far down the cylinder the piston was and cut a piece of plastic pipe that length. Covered it in plastic wrap and inserted it into the cylinder. Now the glued transfer ports will all be exactly the same height, timing and match each other.

I warmed the cylinder with a heat gun and when the Devcon F glue was put in the warm transfer port it ran freely like water and leveled out very nicely. By gluing a port in three stages I could get a very nice curve to the transfer roof. I made the rear ports flat and the main ports angle up at 29degrees.

The great thing about this gluing thing is that its so easy to change. When I finally get the scavenge pattern that I want I will be able to make a permanent copy with a new cylinder.

Pic-1 setting the angle of the port
Pic-2 warming the cylinder
Pic-3 gluing the port, doing this in three stages makes for a nice curved port roof
Pic-4 glued ports and the plastic former

.

SS90

21st September 2009, 03:12

.

Der geht doch ziemlich mager oder?
.

Ja, sicher, aber was ist die Relevanz?
Sie brauchen Hilfe bei der Übersetzung?

SS90

21st September 2009, 03:21

.

Now I have a really good experimental barrel. So I degreed up the motor again at 116 ATDC and measured how far down the cylinder the piston was and cut a piece of plastic pipe that length. Covered it in plastic wrap and inserted it into the cylinder. Now the glued transfer ports will all be exactly the same height, timing and match each other.

I warmed the cylinder with a heat gun and when the Devcon F glue was put in the warm transfer port it ran freely like water and leveled out very nicely. By gluing a port in three stages I could get a very nice curve to the transfer roof. I made the rear ports flat and the main ports angle up at 29degrees.

The great thing about this gluing thing is that its so easy to change. When I finally get the scavenge pattern that I want I will be able to make a permanent copy with a new cylinder.

.

I like the idea of the plastic pipe Teezee, will save quite some time when it comes to finishing up, I recon I will give that concept a shot myself this week.

bucketracer

21st September 2009, 21:35

.

Racing last Sunday at Mt Wellington http://www.flickr.com/photos/dty1/sets/72157622415977724/

.

Buckets4Me

21st September 2009, 21:51

143095

number 0 now under scrutiny

how much nylon has he got ????

dose he need more ???

TZ350

22nd September 2009, 01:29

I like the idea of the plastic pipe Teezee, will save quite some time when it comes to finishing up, I recon I will give that concept a shot myself this week.

Glad you like it, finishing up was easy.

Because of the 24mm carb restriction I am building new cases and a plugged crank with a shorter rod, to "up" the primary compression ratio like you suggested.

Looking at using a RGV250 rod kit which is 5mm shorter than what I had. With the shiny transfers and the higher primary compression ratio, it should go like stink now. :laugh:

.

TZ350

22nd September 2009, 03:38

Racing last Sunday at Mt Wellington http://www.flickr.com/photos/dty1/sets/72157622415977724/

Some of the quick ones. And pic-1 is Avalon 16years old and she's off to Italy to try out for the RedBulls.

.

ajturbo

22nd September 2009, 06:23

143095

number 0 now under scrutiny

how much nylon has he got ????

dose he need more ???
if that had happened down here in wellington, and it had a racer from wellington.... he would have been able to save that little "slide"!!!

koba

22nd September 2009, 06:59

143095

number 0 now under scrutiny

how much nylon has he got ????

dose he need more ???

Brilliant Photo.

F5 Dave

22nd September 2009, 09:31

well he's still got his hand on the throttle. No impending crash that can't be saved by gassing it more.:crazy: Maybe he did save it:yes:

ajturbo

22nd September 2009, 11:23

well he's still got his hand on the throttle. No impending crash that can't be saved by gassing it more.:crazy: Maybe he did save it:yes:
yes dave... if you re-look at the photo, it appears that he is RE-mounting the bike.....

he did save it.... we mush ave taught him well:woohoo:

Buckets4Me

22nd September 2009, 12:54

yes dave... if you re-look at the photo, it appears that he is RE-mounting the bike.....

he did save it.... we mush ave taught him well:woohoo:

the photo before shows the front tire being pulled off the rim.
no he didn't save it. He's only a B grade rider (hope he put his Taupo form in)

bucketracer

22nd September 2009, 15:49

.

The full sequence of photos:- http://www.flickr.com/photos/dty1/sets/72157622415977724/?page=32

.

F5 Dave

22nd September 2009, 17:55

Still got his hand on the throttle "I can save it". I like his optimism.

SS90

22nd September 2009, 19:39

Glad you like it, finishing up was easy.

Because of the 24mm carb restriction I am building new cases and a plugged crank with a shorter rod, to "up" the primary compression ratio like you suggested.

Looking at using a RGV250 rod kit which is 5mm shorter than what I had. With the shiny transfers and the higher primary compression ratio, it should go like stink now. :laugh:

.

That's the spirit Teezee!;)

TZ350

25th September 2009, 22:16

If you want to plan your ports using Jennings or Blairs methodology then this very good and inexpensive software is just the ticket.

http://www.porting-programs.com/

I have always known about Port/Time/Area but found it difficult and cumbersome to do, but with this software I am finding its easy (but still time consuming) to develop a porting plan for my new cylinder for Taupo.

PortMap Porting Calculator

Program features:

* Calculates port heights from durations, or port durations from port heights
* Assign fixed relationships between transfers and exhaust port. Enables all transfer
port heights to be calculated automatically by just entering exhaust timing
* Exhaust and main transfer timing can be entered by mouse click on graph, or typed in
* Calculates required ranges of Jennings or Blair angle areas, mean areas and time areas
* Adjustable graph rpm scale: 7k scrollable range, adjustable from 1k to 18k
* Calculates possible ring flutter rpm
* Mean piston speed
* Suggests carburettor size
* Power meter (you input expected bmep value). Switch between PSI & HP, or BAR & kW
* Port design in separate cad window: enter shape values, or drag port cursors
* Limitations on CAD: Single exhaust port, single boost port

Port map analyzer

Calculate your angle areas, mean areas, or time areas in minutes, directly from the portmap image:

* Load png or jpg port map
* Enter bore, stroke, conrod length and deck height
* Mouse click once on each port to start port trace
* Enter port height to top of barrel
* Set horizontal and vertical cursors to calculate image pixels/mm
* Enter port angles
* View exhaust and transfer rpm ranges in angle area vs rpm graph
* View time areas and power, with adjustable rpm and high-low tranfer bmep
* Change bmep and power units between psi/bar, hp/kw
* Measure portmap horizontal (mm, cord, %bore), and vertical (mm, crank degrees) distances

Welcome to porting-programs.com 2 Stroke porting software for the enthusiast http://www.porting-programs.com/

TZ350

26th September 2009, 08:17

.

One of the things I like about the software from porting-programs.com 2 Stroke porting software for the enthusiast http://www.porting-programs.com/ is that it makes it very easy to get the true total and mean port areas of the transfers.

You input the port window as measured then the horizontal and vertical angles of the port and corner radiuses and the program draws the port and displays the true total and mean areas.

When you select the rpm and bmep (power) you want it displays the port/time/area requirements as espoused by Jennings and Blair. Then gives you a running total of your ports as you modify them on the screen. It pays particular attention to the blowdown port/time/area requirements as described by Blair.

Basically this software is the tool for doing what is in the Blair and Jennings books and you can toggle the software between them.

All this for less than $30 US.

.

TZ350

28th September 2009, 03:05

TZ350

28th September 2009, 18:04

.

Expansion Chamber Design According to Blair:-
http://members.bellatlantic.net/~vze2p5sj/modelengines/expcham.htm

.

DELLORTO

28th September 2009, 18:48

the photo before shows the front tire being pulled off the rim.
no he didn't save it. He's only a B grade rider (hope he put his Taupo form in)

pffft..... b-grade riders are hardcore!, id rather be at the front of b-grade than the back of a-grade, thats why b-grade riders arnt ashamed of being in b-grade its all about close racing and getting challenged by other riders.

Timber020

28th September 2009, 22:42

Thought I would contribute something, I have only read the first 25 pages so far. Heres a timing wheel.Print it off, glue it to card or plastic, mount on motor and start playing

F5 Dave

29th September 2009, 10:52

What is all this intake/Exhaust valve stuff? :wacko: My reed intake valve opens when it damn well pleases & stays out as long as it wants. I have an exhaust valve on my YPVS but not on the bucket.

Print that out so it's like 200mm di & will need to be on a stiff former so you can bolt with a few clamping nuts to the end of the crank.

Buckets4Me

29th September 2009, 12:38

pffft..... b-grade riders are hardcore!, id rather be at the front of b-grade than the back of a-grade, thats why b-grade riders arnt ashamed of being in b-grade its all about close racing and getting challenged by other riders.

you have now upset me !! :calm:

they are at the frount of the B grade because they are either
#1 Burglers
#2 to scared to ride with real racers
#3 want to knock me off ???

they would be mid pack A grade with there times

Henk

30th September 2009, 17:01

pffft..... b-grade riders are hardcore!, id rather be at the front of b-grade than the back of a-grade, thats why b-grade riders arnt ashamed of being in b-grade its all about close racing and getting challenged by other riders.

Wrong, being in B grade is about not being an unpredictable wobbler creating a hazard to the guys at the front of A grade and the problems that the speed differential can cause. I'd rather be mid pack to tail end A grade than burgling the B grade. No chance of that happening soon but when / if I do get the speed up I won't wait to be kicked up a class.

TZ350

30th September 2009, 20:35

.

This is not about B grade riders its Team ESE's thread about engine development.

Bugger off you guys and have your spat some place else. :girlfight: and come back when you have a picture or story about some development work you have been up to on your Bucket.

.

DELLORTO

30th September 2009, 20:39

TZ350

30th September 2009, 20:47

.

Thats what we want to hear. Pictures?

.

speedpro

30th September 2009, 21:51

I have a ram air, made by IHI

DELLORTO

30th September 2009, 22:08

I have a ram air, made by IHI

who's IHI ?? im think about putting my ram air on the cbr, ive been too scared that the EFI wont like it and start to be a pain,

also my ram air is still in development, im gong to fit it with a fan {borrow without permission from electro tech at school:whistle:} that will hopefully spin and blow air into the engine, therefore making the ram air much more efficiant. -max

bucketracer

30th September 2009, 22:16

who's IHI ?? im think about putting my ram air on the cbr, ................im gong to fit it with a fan............therefore making the ram air much more efficiant. -max

IHI......is a make of turbocharger, perfectly legal for Buckets ;)

.

SS90

1st October 2009, 04:53

.

Well its official, the simple setup is the best bang for bucks. Spent a very enjoyable afternoon with Buckets4Me dynoing his RS/GP125 team ESE bike, for a solid wide phat 18rwhp. He has always had the better bike at Mt Wellington and at Taupo it finished 2nd in one of the races.

The mode’s are:- 1.5mm from the top of the barrel, 2mm “O” ring for a head gasket, std head, kX80 ignition fixed at 22deg, std exhaust port, std inlet and timing, std carb, 100 main jet and a RG250 pipe and bingo you have 18rwhp.

.

I was wondering Teezee, what are the exhaust port specs of an original GP125?

I suspect that the exhaust port won't be anywhere near as wide as it could be (although, I suspect the OEM piston rings may be too thick for the 72% than you know you can run with you more modern piston)

With the Polini 130cc engines I do, I am able to run 70% safely (original piston) and get my time area where I need with-out raising the duration.

Using a "racing piston" I can run 75%

As you know, widening a port will increase it's time area, not it's duration, and while it will have a slight effect of raising the RPM where maximum power is delivered, it is FAR less that raising the height of the port alone to gain more time area......

I wonder if you could run the original set up that Chambers bike has, and simply widen the exhaust port as much as is safe, and calculate your exhaust port time area from that.

My experience has been simply widening the exhaust port (assuming the port is reasonably narrow to start with) to get the time area I want has time and time again proven to be the biggest single gain in power as far as cylinder modifications go.

I guess it come down to the thickness of the rings on the original piston.

This is the reason I used a bridged port on the cylinder I made.

Apparently there is a 4% reduction of flow in an exhaust port with a bridge, compared to one with-out, but the extra width the bridge allows you is well worth it in my opinion, as you are only limited by the risk of short circuiting of the transfers and exhaust, and (possibly) localised heating of the exhaust side of the piston crown.

I recon you could see the same power as your current engine with the application of some lessons from your development.

I believe you could see 20 PS and 17NM from slight modifications to Chambers engine, all below 9000 RPM.:yeah:

That's what make Speedpro's engine so interesting too me, he has the time area with-in "norms", but with his set up, I just see his duration as too short, especially considering that more duration on the transfers will increase his torque.

I guess a dyno will tell the story!

I really think you can make the tractor you want from a GP125, but still making 20PS!, but at lower revs.

F5 Dave

1st October 2009, 08:30

Most modern bridged ports don't look like older ones so are likely to flow better & maybe meet that 4% you talk of. They aren't straight edged like earlier ones.

TZ350

1st October 2009, 16:39

I was wondering Teezee, what are the exhaust port specs of an original GP125?

I wonder if you could run the original set up that Chambers bike has, and simply widen the exhaust port as much as is safe, and calculate your exhaust port time area from that.

Your post is encouraging, and its where our thinking is now. Its pretty much what barrel number two was supposed to be but I cut the ports to big/high.

Would you call the Kawasaki KX125 motocross piston I use a "race piston" suitable for an exhaust width of 75%? I have been running 71% with it OK and see Blair also talks about 75%.

I will now start on barrel number three and base it on Blairs book.

.

TZ350

2nd October 2009, 10:59

.

Another interesting pipe design program:- http://www.mh-aerotools.de/airfoils/javapipe_en.htm

.

F5 Dave

2nd October 2009, 11:34

Pussies, I've run close to 80%. But I'm 'special';)

Buckets4Me

2nd October 2009, 16:56

Pussies, I've run close to 80%. But I'm 'special';)

is that run close to
or ran close till :angry2:

TZ350

2nd October 2009, 21:30

I was wondering Teezee, what are the exhaust port specs of an original GP125?

I really think you can make the tractor you want from a GP125, but still making 20PS!, but at lower revs.

Std GP 125 exhaust port width 36mm, 64% of bore diameter, opens 86 deg ATDC.

Working Jennings Port/Time/Area’s at 9,000rpm
(Exhaust 0.00014 to 0.00015, Transfers 0.00008 to 0.00010, Disk Valve Inlet 0.00018 to 0.00019)

I get:-

Ex opens 86 deg ATDC for 188 duration and port/time/area of 0.00015

Blowdown 28 deg

Transfers open 116 deg ATDC for 128 duration and port/time/area of 0.00010

Inlet, 26mm dia port (24mm carb) opens 145 deg BTDC and closes 55 ATDC
230 degree duration and port/time/area of 0.00012

And if the rotary disk is cut for 145/85 port/time/area becomes 0.00014

So even at 9,000rpm the limiting factor still looks like the carb size.

But, like you, I think the GP still can be improved.

.

SS90

3rd October 2009, 02:16

Wow, the GP125 really are pretty good standard!

The numbers you posted pretty much fall in what I would be aiming for on a Polini cylinder.

As a matter of interest, what is the time area of the exhaust if you widen it to 72%?

If it is too extreme, you always have the option of removing material from the cases, (or the bottom of the cylinder) and bring the duration down to compensate, It will require a little work with the transfers, but I think it would be an "easy" option.

The Kawasaki pistons you posted would quite likely fall into the category I would deem "racing". Personal experience with Japanese pistons in the last few years has shown that 75% is ok.

The most powerful (unbridged) cylinders I see/make are always wider than 72%

I occasionally hear of people exceeding that (no problems) but I suspect regular ring replacement is needed!

The 2 pictures I have included show what I use with a Polini small frame cylinder.

As you know a Trapezoid is the best shape, the second picture is a completed work (after honing)

TZ350

3rd October 2009, 08:53

Buckets4Me

4th October 2009, 22:16

found out how TZ350 is getting his bike to go so fast cheaply

http://farm3.static.flickr.com/2472/3812676574_62e2e73840_o.jpg

he has child labour (just like fishy but this time it's his youngest grandchild)

SS90

7th October 2009, 04:11

.

Hi SS90 thanks for your reply and pictures nice work. It is interesting to hear that you have been able to run exhaust ports at 75%.

I make the Ex port/time/area of a standard GP125 widened to 72% at 0.00018. The std GP125 exhaust port is very square and the ones I have modified became elongated ovals. I will take some port tracings and pictures.

At the moment I am most interested in making sense of the blow-down period. There is plenty of info about port/time/area requirements for the ports but in spite of its importance I have found very little on blow-down time/area.

Pic's of a standard GP125 exhaust port. In pic-1 you can see on the very straight top edge where the ring has snagged and worn the edge away. When I widen the exhaust port I curve the top a little more and increase the radius's at the sides.

.

The picture of the port map I posted is at 72%, (57mm bore, 51mm stroke) and I know you can run this with the standard 1.5mm Polini rings and piston.

I recently found a supplier who sells 1.5mm rings to fit this piston, but the word is they can run upwards of 75% no worries, (and cost less than original.)

Anything "high revving" (race style) I would expect to see a quality piston with 1mm rings, and these are what I use to get 75% safely.

I do occasionally hear of over this figure tho........

Interestingly, the design of this particular aftermarket piston was born from a TZR250! (just a little different)

I will see what is available on blow down times over here, but most stuff I know came from personal experience, and I suspect others have found the same, and I have never read anything helpful yet!

TZ350

7th October 2009, 19:18

.

Modified transfer ducts on number two cylinder and 72% exhaust Port.

.

bucketracer

7th October 2009, 21:11

TZ you really have opened those transfers up, they look like open cast gold mines. Having bigger holes to blow through won't do much good if you cant suck enough of the good stuff through the carburetor. What are you going to do there.

F5 Dave

8th October 2009, 08:30

Pass the Devcon. More direct may be an improvement but I'd be slowly contouring those which will reduce the volume throughout. May help to build up the inside it that is the direction you are after.

bucketracer

8th October 2009, 19:35

TeeZee if your going to try and air cool an RGV cylinder, for what its worth, I scraped this from an RGV site:-

My take on what may work with the RGV ports in general is.

Action - Clean up the intake side of the transfer tunnels, even enlarge them if possible.
Result - to increase mixture velocity at port outlet

Action - Port divider (case side) needs to be rounded rather than knife edged
Result - knife edge seems to cause mixture to cling to tunnel wall, well rounded divider edge allows mixture to flow "along" tunnel wall.

Action - Exhaust port can be enlarged by elongating port "ears" further around bore.
Result - Improves exhaust port flow.

Action - Deburr exhaust port walls and divider, remove casting lump at the corner of the main ex port at the bottom of the "ears".
Result - Increase exhaust port flow.

Action - Raise and level exhaust port height by upto 1.0mm, must blend PV's to suit as well.
Result - Increase exhaust port time/area and angle. Flow.

Action - Raise main transfer ports roof angle upto 1.0mm, blending to outer tunnel wall (to angle the roof upward).
Result - Directs more mixture towards the combustion chamber and helps evacuate exhausts gases. Raises port time/area.

Action - Angle Main transfer ports toward boost port away from the Exhaust port.
Result - To allow cylinder to be evenly filled with mixture and helps evacuate exhaust gas.

Action - Raise Aux transfer port to match Main port height but with a level port roof.
Result - Increase's port time/area, mixture passes across piston crown to reduce crown temp.

Action - Widen aux ports on both sides. 1.0mm each side of each port.
Result - Increases bulk flow of mixture across piston crown at lower pressure with a wider spread to stop flow from being shot directly out exhaust ports.

Action - Reduce area directly below cylinder by partially filling with epoxy putty and shape as desired. Requires volumetric efficiency study/simulation!
Result - Increases primary compression by lowering case volume and increasing pumping efficiency.

Action - Build a pipe to suit the characteristics for the cylinder.
Result - Maximizes engine pumping efficiency.

Pic-1 std RGV cylinder, Pic-2 modified, Pic-3 here you go Stefano Genuine A-Kit HRC ex-Pedrosa RSW250 cylinder, a very special race cylinder and Pic-4 on the left official RSW125 2002 crude, in the bottom Honda RS125 2003 for inshore boat use and on the right my rare official Cagiva Mito 125SP 1995
cylinder.

http://www.rgv250.co.uk/forums/index.php?showtopic=32195&st=80

.

speedpro

8th October 2009, 20:28

RGV ports are already too big for bucket racing. I suspect the time/area values are excessive. I've already built a bucket using one - watercooled, sleeved down 100cc, full crankcase reed TS125 bottom end.

bucketracer

8th October 2009, 20:32

.

But how would it go as an air cooled 125?

Anyway it makes interesting reading and they are pretty pics. Here is a couple more.

.

SS90

8th October 2009, 20:59

Pass the Devcon. More direct may be an improvement but I'd be slowly contouring those which will reduce the volume throughout. May help to build up the inside it that is the direction you are after.

I have to agree there Dave, unfortunatley there are no hard and fast rules for Teezee to go on, and he just needs to have a "suck it and see approach"

It fly's in the face of current tuning practices, but the carb size is the problem!

TZ350

8th October 2009, 21:45

.

But how would it go as an air cooled 125?

.

Interesting pictures but the same old problem, the carb. Max power is really not an option.

SS90 has pointed the way, "less rev's and think tractor".

Number two cylinder pictured is a bit OTT but number three will be more refined and planned.

.

SS90

8th October 2009, 22:12

I'm still looking for some data on blowdown times so you can put some science to it Teezee, a friend is emailing me a scanned article from a magazine (not on blowdown times, but more general stuff, and he is a "genius") it's "Auf Deutsch", do you have a program that can translate from a series of images?

I could translate it if needed, but it will possibly take 3 or 4 days.

speedpro

9th October 2009, 12:27

Finally I know what it's like to work at ESE, 1:26pm on a Fri, browsing Kiwibiker. Excellent :Pokey:

TZ350

9th October 2009, 20:53

Finally I know what it's like to work at ESE, 1:26pm on a Fri, browsing Kiwibiker. Excellent :Pokey:

:Oi: Boss, not me I was out on a job at that time.

.

bucketracer

10th October 2009, 09:51

.

Here is a xls spread sheet that can be downloaded that is based on MacDizzys work and covers blowdown time area:- www.essjayar.com/motorbikes/2_stroke.xls

.

TZ350

10th October 2009, 18:30

.

Thanks Bucketracer for the link, very interesting, I have had a look at it.

I always thought of the blow down phase as starting when the exhaust port opens and ending when the transfer ports open. But I recently came across a better definition that makes more sense.

Its “The blow down phase starts with the opening of the exhaust port and finishes when the pressure inside the cylinder equals the pressure in the exhaust pipe”. from "The Internal-combustion Engine in Theory and Practice"

Makes sense to me, from this I can see that blow down may/or may not be complete by the time the transfers open. Then after blow down I guess there is a period of suck down, from the kinetic energy of the slug of gas traveling down the exhaust header before/as/or while the transfers open.

I am not sure about the ideal timing of this suck-down phase.

.

TZ350

14th October 2009, 15:05

.

Thomas and Tuti have got themselves a new toy to play with, a V8 Maserati engine.

Beats mucking about with those old Leyland P76 alloy V8's.

.

TZ350

14th October 2009, 15:25

.

NedKellys team ESE bike was run up on the dyno again after Thomas had done some porting work, he managed to get a similar flat torque curve like Chambers 18hp bike on post 1222 page 82 but NedKellys makes 2 more hp.

Suzuki GP125

Pic-1 Ex opens 84 degrees ATDC at 64% of bore width. Trans open 114 ATDC, Inlet opens 145 BTDC and Closes 55 ATDC ignition 24 BTDC non-squish std open chamber head. 24mm carb 105 main jet and RM pipe.

Pic-2 Changes are:- Ex opens 79 ATDC at 70% bore width.

I have not been able to analyze the port/time or blow-down yet but suspect it will be revealing. I am still working on my own cylinder and bottom end where I have been working on unmasking the transfers like SS90 suggested. I am finding that converting the idea to reality is a bit tricky but if I can get more torque from my own bikes engine it will be worth the effort.

Team ESE now have 2 bikes at 20rwhp and 2 at 18rwhp the difference between them seems to be the width of the exhaust port, in every other way they are much the same.

.

ajturbo

14th October 2009, 16:42

ok..... on this note... is there somewhere in wellington that us Bucket racers can get dyno'ed for free..???

is there anyone out there(here in welly) that has one (eg: like Pete sales has ) sitting in back of garage, just wanting to be used?... just so we can tune/brag/laugh????

F5 Dave

14th October 2009, 17:09

Of course, people are always offering dyno services for free. Pete never charges does he?:lol:

koba

14th October 2009, 17:50

.

NedKellys team ESE bike was run up on the dyno again after Thomas had done some porting work, he managed to get a similar flat torque curve like Chambers 18hp bike but with more hp (20rwhp).

Suzuki GP125

Pic-1 Ex opens 84 degrees ATDC at 64% of bore width. Trans open 114 ATDC, Inlet opens 145 BTDC and Closes 55 ATDC ignition 24 BTDC non-squish std open chamber head. 24mm carb 105 main jet and RM pipe.

Pic-2 Changes are:- Ex opens 79 ATDC at 70% bore width.

I have not analysed the port/time or blowdown yet but suspect it will be revealing.

.

Thats looking pretty good!

speedpro

14th October 2009, 19:32

extending the base line like that really distorts the curve

bucketracer

14th October 2009, 20:04

extending the base line like that really distorts the curve

Not sure what you mean, both graphs are 6k wide along the base line, in fact all the ESE dyno graphs are 6k wide. Do you mean that if they were charted over a 12k base line they would be more realistic?

The graph in the first pic is making power from 7.5k to 9.5k a power band 2k wide more or less and the second graph has the power from 8-11k, a 3k wide power band. A 50% increase, not too shabby.

.

speedpro

15th October 2009, 17:56

The increase is good, it is all about area under the line, to a point. I'm just used to looking at graphs that show a wider range of revs. My old MB sidecar made over 14hp from 9-13,000rpm with a peak of 19.9hp over about a 1000rpm. 28mm carb and single sided reed with one big petal.

TZ350

15th October 2009, 20:07

.

extending the base line like that really distorts the curve

I agree, even a very peaky power curve would look flat if it was drawn on a six foot wide piece of paper.

The dyno data was only recorded in the rev range of interest and I imagine that the dyno software adjusts the axis of the graph to suit the rpm range and power curve its graphing and automatically fits it all to the A4 size paper printout.

And certainly if the dyno data was recorded from a much lower rpm the torqe curve would appear relatively shorter on the graph.

Your right the printed torqe curve would only be half the size if it was graphed 0-12,000rpm instead of 6,000 to 12,000.

But the torque curve would still cover a band of 3,000 rpm although it would be harder to see and half the graph would cover a lower rpm range that's of no interest.

Reality can be very hard to measure.

.

SS90

15th October 2009, 20:55

Your right speedpro, but think of it this way,

When you Dyno soomething like, say an RS125 (which you only operate above 8500 RPM anyway), why would you bother graphing anything below that.

I think it would be fair to say that not many tuned 2 stroke buckets are operated below 6,000 RPM anyway, so why even bother "testing" then at that rev range.

Personally, I start dyno runs on the stuff I do at 4,000 RPM.

There is just no reason to measure lower.

Another point is that it is important to keep a constant exhaust temperature when making a two stroke dyno run, or rather, allow the exhaust to (at least) get to the correct temperature.

If you "bog" the engine down when trying to do a run, you can often cause the exhaust not to get up to the right temperature, giving incorrect readings. (exhaust temp gauges are really helpful)

The best thing is to operate the engine during the run, so that it accelerates the same way as it would if you where "on the track"

I.E, if you shift from 2nd to 3rd gear, the revs arent likely to go below 4,000 (or 6,000 in this case) anyway.

If they did, you are doing the run in the wrong gear!

I also feel that by the design of the pipe they are using, there will be a "resonance hole" about, 4,500RPm anyway....... no point in measuring that!

TZ350

16th October 2009, 16:04

.
Chambers and Thomas checking the vertical wheel alignment of one of the Team ESE bikes after it had taken a heavy hit. The whole frame had become twisted.

.

TZ350

16th October 2009, 16:09

Another point is that it is important to keep a constant exhaust temperature when making a two stroke dyno run, or rather, allow the exhaust to (at least) get to the correct temperature.

If you "bog" the engine down when trying to do a run, you can often cause the exhaust not to get up to the right temperature, giving incorrect readings. (exhaust temp gauges are really helpful)

I had not realy thought about it but it makes sense and might explain why my bike allways ran better when the pipe got hot.

.

F5 Dave

16th October 2009, 16:24

Funny usually the first runs are the best until the crankcase warms up. I always run through gears a few times before taking any real note of readings.

TZ350

16th October 2009, 18:02

.

It was suggested at the time that the pipe was a little long for the porting and as it heated up it mached it better. Possible I guess.

.

SS90

16th October 2009, 21:32

F5dave makes a good point, there is always a "slightly better" run when the engine is warming up, and once it is up to N.O.T, the runs remain constant. (always good for the customer who want's to beat his mates), of course until the engine gets too hot, when it drops dramatically.

With the pipe temperature I have actually seen 3 pipes that work really well (older designs) but, lets say you where racing in a 20 lap race they actually gradually overheat the engine and sometimes actually seize, (or worse and hole a piston) whereas in a 12 lap race, they work fine.

You notice it late in the race, when for no apparent reason the EGT starts slowly climbing.

To be honest I really have not been able to put a real reason to this happening, but notice that it's the stinger (pipe "bleed valve") that seems to be the cause.

Not so much the diameter, as I suspected, but more the design of the muffler.

For example, the "modern" 2 stroke muffler hasn't changed since the eighties, and there seems good reason other than styling, the older style (that you see in older books) effectively muffle the exhaust, but it seems does cause the pipe to overheat (in longer races)

Like you say Teezee, your pipe could well be too long, or even, you may just need to take a look at you stinger design, not so much the muffler, (as you have a modern design), but more the diameter and perhaps length.

I simply use the old technique of having the stinger section as a "sliding joint", and where the stinger meets the baffle cone, instead of welding it in place (for testing) simply have a screw clamp joint, so you can slide a (longer, or indeed, shorter) stinger section in and out of the baffle cone.

You can find power this way (surprisingly), and you will instantly lose noise!

Just don't go past the medium point of reflection!

There are plenty of two stroke exhaust now that essentially have the muffler attached straight to the baffle cone, and the stinger section (that what does not include the muffler portion) is simply "slid inside" the baffle cone.

TZ350

17th October 2009, 08:10

.

Interesting SS90, a lot to think about there. Currently my muffler is an old one of an RG250 that has had the crud burnt out of it a typical Bucket muffler. I recently acquired of Trademe two very near new mufflers from 125 MX bikes. I figured they would be a better design than I could make myself.

Apparently the customers wanted a better sound????? suits me, I want a quiet Bucket, which is better for sneaking up on the competition with. I have found, if they don’t know your there you stand a much better chance of diving under them into the next corner.

Speedpro also recently talked to me about people slipping the stinger inside the chamber. My new mufflers have different stinger diameters so I should be able to try your suggestion.

I want to make a new pipe, actually several straight pipes with sliding mid sections for testing on the dyno like I saw in an attachment you posted. I could also incorporate a sliding stinger as well, in fact that’s a very good idea, thanks.

There is a lot of work in planning the chambers and making them so it wont happen overnight but it will be worth the effort. I have spent nearly 100 hours building a new motor to try the “unmasking of the transfers” “port/time/area” and larger “inlet port” ideas of breathing better and for the right time talked about before, a lot of work for just a little more torque!!!!.

.

SS90

17th October 2009, 08:44

Yea, I can relate to that.

The big gains are the easy ones, and the stuff that "sets you engine apart from others" takes time, but it all adds up.

20PS is really good though, and like you say, getting it at lower RPM is what it is all about.

It helps your sanity when you think about any gains in a %age of your base run.

1 PS (or 1NM) becomes a bigger number when you think of it that way!

gav

17th October 2009, 21:59

TZ350

17th October 2009, 22:42

.

A while ago Thomas told me that if I wanted more power the pipe had to be made longer. Well like most, I new that a pipe needed to be shorter the higher the RPM and thought he was wrong.

And I have always been curious about why someone at Buckets was able to run an RS125 pipe on their TS125, I couldn’t understand how a pipe for a high rev high power motor could work so well on a low rpm 18hp bike.

Recently I wrote a spread sheet based on Blairs work so I could sort out a pipe for my new engine. What I didn’t realize is that a pipe needed to be longer for higher Hp engines because of the higher average exhaust gas temperature. So a pipe gets shorter as the rev’s go up and longer as the hp increases.

Here I have graphed the tuned length as a function of Hp vis RPM for an Ex port duration of 198 degrees.

……….….18hp…….20hp……..22hp……..37hp
RPM
..9,000……917…….1005…….1085….. Tuned length in mm
..9,500……868……..952……..1028
10,000…..825……….904………977
10,500…..786……….861………930
11,000…..750……….822………888
11,500……717…….…786………849
12,000……688…….…754………814……..840 Honda RS125
12,500……660….……723………782

Ex Temp…350………475………600……...650 average exhaust temp Oc
BMEP……5bar………8bar……..9bar……..11bar

It makes sense that a pipe gets shorter as the rev’s go up because there is less time for the pressure wave to travel out and back through the pipe.

Hp and Ex Temp are functions of BMEP the higher the BMEP the higher the measured Hp and hotter the average exhaust temperature is.

A pressure wave travels faster in a hotter exhaust so the more hp the motor makes the longer the tuned length needs to be. It was a surprise to me that a Honda RS125 pipe with a tuned length of 840mm could be used on a 9,750rpm 18hp TS125.

Exhaust port duration also has an effect on the tuned length. Keeping the Hp and RPM the same I graphed the change in tuned length for a range of exhaust port duration’s.

Ex Opens ATDC Duration Tuned Length

…….87………...……186…....….943
…….85…………...…190....…….964
…….83…...…………194…....….984
…….81……...………198…......1004
…….79………...……202…......1024

And that makes sense too as the longer duration means more time so the pressure pulse can travel further.

So there it is:- more rev’s and the pipe becomes shorter, more power and/or duration and the pipe becomes longer. Not what I had thought at all.

So Thomas was right, a pipe needs to be relatively longer for a motor that is making more Hp.

.

TZ350

17th October 2009, 23:01

Wonder what these would be like? $89- each.
http://www.trademe.co.nz/Trade-Me-Motors/Motorbikes/Parts-for-sale/Exhaust/auction-247170189.htm

Tempting, certainly worth a look.

.

SS90

20th October 2009, 07:22

F5 Dave

20th October 2009, 08:24

Quite a torturous path to follow for the boosts, but no more so than as an extn of the 2ndrys as per Suzuki of the era (late 70s). That must have been from a TZ500 where they were still running piston port rather than reed hence couldn't run normal boost port. Early 80s? More late 70s. But they kept with the piston port engines a they made more power than reed at the time. No sign of powervalve but there is a ex boost port. Sidecars kept these going somewhile longer where the high output was important & the peaky nature not so with many spin off engines from Dutch tuners (memory failing Henkel or Heiniken or something, it will come to me). [edit Krauser was one). When did they start with electrofusion over chrome? that may id the cylinder a bit.

Must have run a single ring peg centrally.

TZ350

20th October 2009, 10:53

These 2 pictures arrived today, I'm not 100% sure, but the cylinders are off a Yamaha from the early eighties belonging either to Johler Harald or Emmerich Stenger.

Thanks, very interesting pictures, very radical, what I love is, its the sort of thing that can be tried on a bucket. I am impressed.

.

F5 Dave

20th October 2009, 11:50

Ohh look, my Yamaha factory & Production road racing 2 stroke 1955-93 book has just today arrived from Amazon (along with Cameron's Grand Prix Motorcycle book). So I might be able to anorak an answer after a few nights.

Kickaha

20th October 2009, 18:36

Sidecars kept these going somewhile longer where the high output was important & the peaky nature not so with many spin off engines from Dutch tuners (memory failing Henkel or Heiniken or something, it will come to me). [edit Krauser was one).

Hummel? although I think he just did tuning or maybe his own barrels for TZ based stuff

Krauser, ADM, BRM, Swissauto http://www.flickr.com/photos/teamheronsuzuki/sets/72157594371961909/

sonic_v

21st October 2009, 09:25

F5 Dave

21st October 2009, 09:44

Hummel? although I think he just did tuning or maybe his own barrels for TZ based stuff

Krauser, ADM, BRM, Swissauto http://www.flickr.com/photos/teamheronsuzuki/sets/72157594371961909/

I thought I'd seen Hans Hummel barrels (note that pic of Krauser has HH marked on barrels). Sounds Dutch. Oops he's Austrian.

Either way I'm clearly no expert on the subject & someone is likely to come along & point out that the barrels are from a Griffen 360 marine compressor.

bucketracer

25th October 2009, 19:07

.

Some handy hints on making cables:- http://www.dansmc.com/solder_cable.htm

.

bucketracer

25th October 2009, 22:35

.

It might be a 12A Rotary exhaust port but there is some interesting ideas about testing and port radiusing applicable to 2-stroke exhaust port shaping. A simple flow bench could be made from a vacuum cleaner and home made manometer like TeeZee used for testing his carburetors. http://www.yawpower.com/Flow%20Testing.html

.

TZ350

30th October 2009, 11:25

.

Next years project.

A RGV250 cylinder fitted to a GP100 crankcase, now do we air cool it or sleeve it back and devcon up the transfers to get the correct port/time/area for a water cooled 100cc with a big carb?

Thomas is also toying with a supercharged 99cc 4-stroke.

.

F5 Dave

30th October 2009, 16:21

The cleanest best way to power will be as a 100.

The two things working against you is an extra heat inducing sleeve & the positions of the ports as they progress inward if you think about it.

& a 5 speed gearbox. oh dear.

Maybe a 125 would be a better route. But will the RGV produce a wide enough torque curve for the aforementioned 5 speed gearbox esp as compression etc will need to be lower with aircooling?

Only thing is not many cases will take such a large barrel. Your GP still requires quite some welding fabricating to put in studs to hold that down securely, obviously just sitting it there is not even 1/2 the job as I'm sure you're aware.

An RGV250 bottom end would be too big. . . . Maybe. RGV150 bottom end might be ok but the SS150 racers will have scooped up most of them.

Buckets4Me

30th October 2009, 20:32

Only thing is not many cases will take such a large barrel. Your GP still requires quite some welding fabricating to put in studs to hold that down securely, obviously just sitting it there is not even 1/2 the job as I'm sure you're aware.

dam you I was thinking that my next hotrod engine was nearly finished
and you go and spoil it like that :no:

dont burst my bubble :doh:

I was also wondering what those guys where doing with rotary engines ????
and what cc can they be to run in a bucket ??

TZ350

30th October 2009, 21:14

Only thing is not many cases will take such a large barrel. Your GP still requires quite some welding fabricating to put in studs to hold that down securely, obviously just sitting it there is not even 1/2 the job as I'm sure you're aware.

On our setup the barrel requires a 10mm spacer, I have found that I can bolt it down using three of the original GP stud holes and only need to add a fourth. The barrel itself will be held down by studs screwed into the spacer plate.

Marking the plate out was a bit tricky but Thomas managed to get all the holes in the right places. The next trick is to cut a hole for the cylinder spigot and transfer cutouts. The spacer plate is being made out of steel for strength and will be surface ground to thickness to set the final piston/deck height.

Like you say Dave there are pro's and con's between the 100/125 configurations and we are still debating which way to go, thank you for your ideas, it all helps.

As is, I have heard that the RGV cylinder is short on blow down time/area, but this could be a handy thing. Because the transfer ports are so wide their roofs could be devconed down thereby increasing the blow down time/area and still have plenty of transfer port/time/area for making a more tractable engine that runs "phater" at lower revs.

.

F5 Dave

31st October 2009, 11:01

Spacer plate is a great idea, but you would need to lose some of that height from somewhere, obviously a longer rod would help & it is possible that the RGV barrel matches to a taller bottom end, in which case very lucky.

TZ350

31st October 2009, 11:40

.

RGV rod is 5mm longer than a GP one and the RGV case crank and piston crown heights are a little different too. The total difference is a little less than 10mm hence the final adjustment of the spacer plate to get an accurate piston/deck height.

.

TZ350

31st October 2009, 12:10

.

I know a carb's size is measured across the throat next to the slide because that is usually the narrowest point of the carbs venture. But.........

Dave is a 32mm carb with a 24mm venture inserted into the rear away from the slide still a 32mm carb or is it a sleeved down big carb that meets the 24mm carb rule for F4 125 2-strokes.????

I see in the posts about the GreyMouth races the fast F4 2-stroke was referred to as having a sleeved down big carb, clever idea as it moves the point of maximum air velocity away from the point of maximum disruption around the slide. And I think bulk air flow could be improved that way.

Its an idea I would like to try myself if its legal, any one know?????

.

bucketracer

31st October 2009, 15:33

.

Using a venture instead of a throttle plate in the carburetor to controle engine speed...........

Venture throttle:- http://www.prvperformance.com/PRV_induction_technical_overview.pdf

.

speedpro

31st October 2009, 18:49

venturi, lok it up

bucketracer

31st October 2009, 19:48

venturi, lok it up

Using a venture.........:Oops:..........venturi

.

Chambers

31st October 2009, 21:57

Rule 24-2-4 F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm carburator. Can this mean a big carb with a 24mm restriction??????? Does anyone know, I to would be interested.

speedpro

31st October 2009, 23:29

"I" would think that any carb would be OK as long as at some point within it the cross-sectional area was equivalent to a single 24mm diameter orifice.

speedpro

31st October 2009, 23:32

I have some bits for an RGV250 here somewhere including alloy rings to fill the space between the standard head gasket and a 100cc bore.

TZ350

1st November 2009, 08:33

.

Hi Chambers I remember you talking about making a carburetor that was a simple tube with a plug.

Look at the link that Bucket posted, http://www.prvperformance.com/PRV_induction_technical_overview.pdf

The right hand picture shows a system like you were describing.

I think your idea is good and will give it a try.

.

TZ350

4th November 2009, 16:16

.

Found that an old Honda RS125 pipe is close to what I need for my new engine and has the right tuned length and other features for making max power at 9,500 rpm on my GP.

Pic-1 welded a new flange to the header
Pic-2 the RS pipe tucks under the frame realy nicely with out having to change anything
Pic-3 pipe was cut at the mid section seam and turned so that the exhaust exits at a better angle

All in all it was very easy to fit the RS pipe to my GP.

With all the porting work and the new RS pipe the hope is we will get a wider power band and 20 possibly 22RWHP at 9,500 rpm. I am still 2-3 weeks away from getting the bike on the dyno, but very much looking forward to seeing how it all works out.

I have kept the old motor and pipe complete so that I have something to fall back on if the new motor turns out to need more development.

.

F5 Dave

4th November 2009, 16:20

Those old RS pipes tend to want to rev & rev & rev (good for top speed, not always so good for cranks).

bucketracer

4th November 2009, 18:39

All in all it was very easy to fit the RS pipe to my GP.

Whatttttttttt....:Oi:....No way TZ

can you take a pipe from a high revving high power motor and fit it to a low spec plonker and expect it to work.

.

Buckets4Me

4th November 2009, 19:52

Whatttttttttt....:Oi:....No way TZ

can you take a pipe from a high revving high power motor and fit it to a low spec plonker and expect it to work.

.

:lol: next you will be telling us that your not ment to slap a supercharger (not an expantion chamber) on an old heap of junk either ? :Pokey:

do us a favor and wave as I leave you behind at the start line :girlfight:

sonic_v

5th November 2009, 00:11

Is that the rs pipe from a 88-94 bike. I seem to recall that this pipe had a tuned length of about 816mm. Even with a low exhaust port setup I suspect your engine will peak at 10,500 revs plus.

Buckets4Me

5th November 2009, 11:58

10500rpm is closer than the 11400rpm they peak at now

http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=146761&d=1255490661

jasonu

5th November 2009, 14:06

I fitted a 1991 RS125 pipe to my RG KE 100. It makes 22HP at the wheel at 10500 rpm with no over rev, it just stops dead at 10500. I have another pipe from an old TZ500 GP bike. It makes 25hp at 11200 and holds it until 11600 and will go to 12000. Both pipes give good low and mid range power and have some what similar curves. The RS pipe starts makeing power a bit sooner but as I said, not as much top end and signs off sooner

TZ350

5th November 2009, 15:03

.

Whatttttttttt....:Oi:....No way TZ

On Page 95 post 1417 I tried to explain my understanding of how the three things, rpm, ex duration and ex temperature affect the tuned length required. And the tuned length requirements of a low speed plonker can be the same as a high power racer. Other things like the header and mid section diameter and angles of the diffuser and convergent cone and stinger could be different though.

Is that the rs pipe from a 88-94 bike. I seem to recall that this pipe had a tuned length of about 816mm. Even with a low exhaust port setup I suspect your engine will peak at 10,500 revs plus.

Yes 88-94 chamber I think and you could be right about the tuned length, I found it very hard to measure the imaginary center line that runs down the length of the chamber accurately.

10500rpm is closer than the 11400rpm they peak at now.
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=146761&d=1255490661

I think if I can get the power to peak at lower rev’s and improve the plugging efficency like SS90 discribes then the 24mm carb restriction will be less effective at suppressing peak power.

I fitted a 1991 RS125 pipe to my RG KE 100. It makes 22HP at the wheel at 10500 rpm with no over rev, it just stops dead at 10500. I have another pipe from an old TZ500 GP bike. It makes 25hp at 11200 and holds it until 11600 and will go to 12000. Both pipes give good low and mid range power and have some what similar curves. The RS pipe starts makeing power a bit sooner but as I said, not as much top end and signs off sooner

That’s very interesting, could the difference between the RS pipe stopping dead on your bike and it reving on, on an RS125 be the retarding ignition that the RS uses? do you have any dyno graphs or dimensions of the pipes you could post?

.

speedpro

5th November 2009, 16:18

I was in the kart shop the other day and they had pamphlets on the wall for 100cc engines with either crankcase reed or rotary valve and were quoting 28-30hp with a 24mm carb at 20,000rpm. So I figure if you spin the GP to 20,000rpm with the extra capacity you should be looking at up to 37.5hp, eh?

Buckets4Me

5th November 2009, 16:39

bucketracer

5th November 2009, 19:04

.

On Page 95 post 1417 I tried to explain how the three things, rpm, ex duration and ex temperature affect the tuned length required.

And the tuned length requirements of a low speed plonker can be the same as a high power racer.

.

:doh: yep I went back and read it carefully, I see what you mean.

.

SS90

5th November 2009, 23:41

Just as a matter of interest Teezee, what cylinder head design are you using on the new cylinder?

F5 Dave

6th November 2009, 08:52

stop that now Speedpro :no:
been down this path and it cost $$$
dont get him started again

Well clearly that was a PT by Mike, Kart engines & parts aren't legal (aside from where free rule like pistons, ignitions).

Also no gearbox losses.

jasonu

6th November 2009, 14:12

That’s very interesting, could the difference between the RS pipe stopping dead on your bike and it reving on, on an RS125 be the retarding ignition that the RS uses? do you have any dyno graphs or dimensions of the pipes you could post?

.[/QUOTE]

I'll do my best. However, it was built 10 years ago, I now live in the States and the graphs etc are at my mates place in Titirangi. But I will try.

TZ350

6th November 2009, 19:55

Just as a matter of interest Teezee, what cylinder head design are you using on the new cylinder?

Hi SS90 at first I am planing on using my favorite copper head,, mainly because I have it and to try something else means I have to source suitable 56mm, domed, 16mm pin, thin ring, race quality pistons, may be, something like late 80’s YZ125 Wiseco pistons.

I have a welded up head that I could machine out into a squish configuration and I also have a spare standard open chamber head. If the engine does peak at about 9,500rpm or less, then I think the open head would be worth a try at the lower rpm.

I remember you talking about the benefits of an open chamber head like a std GP has and if the engine works out as planed definitely the next step will be to try an open chamber head on the new configuration engine.

.

TZ350

6th November 2009, 20:43

.

The current challenge is to get more air into the engine through the 24mm carburetor. A carburetor is basically a simple venture. Thomas and I have been looking into how the flow through a venture can be improved.

Picture-01 of a traditional venture (A) and a low loss flow tube (B) where the maximum pressure recovery (flow) occurs when D2/D1 is between 0.6 to 0.7.

Picture-02 a short flow tube (C) with a length 4.5 times its diameter flows more than a carburetor of the same size. Now it would be very handy if the fuel could be atomized into the air before its sucked through the flow tube.

This could be achieved by sticking the flow tube into the rear of a bigger carburetor (D) and then you would have a high flow 24mm carburetor.

Picture-03 It turns out that the optimum ratio is a 24mm flow tube pushed into a 38mm carb.

Picture-04 is a 24mm flow tube/nozzle, press that baby into a 38mm carb body and you could have super efficient 24mm carburetor.

Well that’s the theory anyway and something we plan on trying out sometime.

.

TZ350

6th November 2009, 21:19

.

Anyone have a 38mm power-jet Keihen carb of an RS125 for sale or any jets and needles?

.

xwhatsit

7th November 2009, 11:35

Picture-02 a short flow tube (C) with a length 4.5 times its diameter flows more than a carburetor of the same size. Now it would be very handy if the fuel could be atomized into the air before its sucked through the flow tube.
That's the trouble, isn't it -- I thought the point of a venturi in a carb was to keep flow rate up over the top of the jet. If you put the flow tube in the rear of the carb, flow rate might be high through the flow tube but afterwards it'll slow down once more with the bigger volume, won't it, and prevent good atomisation of the fuel? Or did you mean stick the flow tube after the carb?

Still think somebody needs to try fuel injection in a bucket. Take a flow tube, a simple rotating choke throttle, and an old injector.

bucketracer

7th November 2009, 15:58

.

A bit of info on flow tubes and what they look like in theory.

http://www.cranemfginc.com/PDF/Venturi%202009%20CATALOG-2.pdf

And a picture of what they look like in practice. TeeZee you will need a trailer, they are a bit heavy for a bucket racer.

.

bucketracer

7th November 2009, 16:27

.

Randy Norian's thoughts on tuned inlet design for Motorcycles and still air box design.
http://www.saltmine.org.uk/randy/airboxdesign.html

Randys Home page
http://homepage.mac.com/rg500delta/RandysAddiction/

.

Buckets4Me

8th November 2009, 08:56

Well clearly that was a PT by Mike, Kart engines & parts aren't legal (aside from where free rule like pistons, ignitions).

Also no gearbox losses.

so there is the problem you cant buy the parts you need to make them
and knowing TZ350 that means money :bash:
and time

TZ350

8th November 2009, 14:47

TZ350

8th November 2009, 17:35

Details and pictures of someone fitting TZ barrels to a RG500 the big brother of the GP125.

http://homepage.mac.com/rg500delta/Delta/Delta2.htm#Overallanalysis

The spacer plate idea is what we are trying with the RGV cylinder conversion on one of our GP's

.

sonic_v

9th November 2009, 01:06

.

20,000rpm some how I don't think I will be going there.

27-30 hp at the crank might be possible as people (with dyno graphs) have claimed 20-22-25rwhp for their F4 100's

But 27-30hp with a 24mm carb, don't think so.

.

They certainly give a minimum of 28hp but there are very good reasons for this, most of which cannot be applied to a motorcycle. These engines are the old world championship class "ICA" until about two years ago.

features

1/ Intake uses a diffuser after the carb choke.
2/ High trapped compression ratio - Over 10 to 1.
3/ High crankcase compression ratio.
4/ Static Ignition but with a lot of advance.

The only reason that karts can get away with this setup is the fact that they spend such a short period of time in the power band. Note that even though the engines rev to 20,000 rpm peak power is in the 13,000 rpm range.

TZ350

9th November 2009, 06:33

They certainly give a minimum of 28hp but there are very good reasons for this,

1/ Intake uses a diffuser after the carb choke.

.

Hi Sonic, thanks for your input, carb's and diffusers. Can you tell us more? A picture or discription would be very helpfull. I am very interested in how this is done.

Here is a picture of the carb parts that Thomas has been playing with to try and improve the mass flow through them.

.

k14

9th November 2009, 07:13

.

Anyone have a 38mm power-jet Keihen carb of an RS125 for sale or any jets and needles?

.
You don't need a power jet. What you want is a carb off a 95-96 RS125. Didn't have power jet, those were the last years that the bikes were setup to run leaded fuel. If you get the powerjet carb you'd be looking at $1500+ because you then need to run tps, the full loom and cdi. You can't just block the powerjet off because then it cocks up the whole fueling of the thing!

SS90

9th November 2009, 12:45

They certainly give a minimum of 28hp but there are very good reasons for this, most of which cannot be applied to a motorcycle. These engines are the old world championship class "ICA" until about two years ago.

features

1/ Intake uses a diffuser after the carb choke.
2/ High trapped compression ratio - Over 10 to 1.
3/ High crankcase compression ratio.
4/ Static Ignition but with a lot of advance.

The only reason that karts can get away with this setup is the fact that they spend such a short period of time in the power band. Note that even though the engines rev to 20,000 rpm peak power is in the 13,000 rpm range.

I'm not too sure I would subscribe to the idea that a Kartsport engine spends little time in the peak power range there Sonic.

I am of the opinion that it is quite the opposite actaully!

One of the many things a Kart does well is hold it's corner speed!

You point out that they run "a high Crankcase compression ratio", what do you consider "high"?

Because, what I consider "high" is pretty much anything over 1.45:1 (and for most applications, I would go further to say that over 1.3:1 to be "detrimental" to over all power spread.

Of course expansion chamber design has as much to do with that as anything else.

I am pretty sure that most "fixed gear" Kartsport engines run around 1.25:1, for the very reason that a longer spread of peak power is desireable.

I realise that some Kart engines are very particular about set up (I have minimal experience with these), but i have never heard of a moder 2 stroke engine that revs 7000 RPM over it"s peak power, and has a static curve.

Why would a 2 stroke engine that revs to 20,000 RPM have high advance, when the peak pressure point at 20,000 RPM come a lot sooner that at 14,000 RPM?

do you have some dyno graphs for these engines?

TZ350

10th November 2009, 15:17

.

Will this 50 make it to Taupo? and is the front brake big enough?

To be able to use a better piston than the original I have to use one that is 2mm oversize. And to stay within the 50cc limit I have had to de-stroke the crank 3.5mm, thats shift the pin into the center by 1.75mm. I found I could do this by using an Apprilia rod kit but the bigend pin cuts into the main shafts which could be a problem.

.

speedpro

10th November 2009, 17:40

. . . but the bigend pin cuts into the main shafts which could be a problem.

Which is why I had a pin with an offset centre section made. 20mm ends with a 22mm centre offset .75mm to reduce the stroke 1.5mm.

TZ350

10th November 2009, 18:40

Which is why I had a pin with an offset centre section made. 20mm ends with a 22mm centre offset .75mm to reduce the stroke 1.5mm.

Now that's a very good idea, thanks.

.

TZ350

10th November 2009, 18:42

You don't need a power jet. What you want is a carb off a 95-96 RS125. Didn't have power jet, those were the last years that the bikes were setup to run leaded fuel. If you get the powerjet carb you'd be looking at $1500+ because you then need to run tps, the full loom and cdi. You can't just block the powerjet off because then it cocks up the whole fueling of the thing!

Hi K14 we are getting one of those IngTech ignitions to try out that you told us about. I think the race version we are getting can switch the power jet.

.

sonic_v

11th November 2009, 04:07

Hi Sonic, thanks for your input, carb's and diffusers. Can you tell us more? A picture or discription would be very helpfull. I am very interested in how this is done.

.

The ica 100cc kart engines use diaphragm carbs with a choke size of 24mm. However by the carb exit they have diffused out to 27/28 mm. They bolt directly to the engine manifold and appear to diffuse out in area even more but hard to tell as the profile shape changes to match the reed block. This ibea carb is particularly good. http://www.out2win.com/catalog/images/ibeal5.jpg

The replacement world championship class is now called kf2 and these engines are 125cc with reed induction and powervalves. They use the same 24 mm carb design. the l6 carb shown here is homologated for this class. http://www.out2win.com/catalog/ibea.html

People are claiming 38hp plus for these engines. Clearly the carb is not holding them back too much!!!!

The 24mm carb rule is not the limit in horsepower development for a bucket that people think it is provided you use a diffuser. A 30mm at most area inlet port for a disc valve is all that is required with a nice tapered diffuser. Any bigger than 30mm will be a waste of time.

TZ350

11th November 2009, 05:34

People are claiming 38hp plus for these engines. Clearly the carb is not holding them back too much!!!!

The 24mm carb rule is not the limit in horsepower development for a bucket that people think it is provided you use a diffuser. A 30mm at most area inlet port for a disc valve is all that is required with a nice tapered diffuser. Any bigger than 30mm will be a waste of time.

Thanks Sonic_V thats very interesting, very encouraging, seems like Thomas and I are on the right track.

.

sonic_v

11th November 2009, 07:28

k14

11th November 2009, 07:59

Hi K14 we are getting one of those IngTech ignitions to try out that you told us about. I think the race version we are getting can switch the power jet.

.
Yes but still, the powerjet is for unleaded fuel. It is useless for running leaded. Stick to a 95-96 and you will get better results.

sonic_v

11th November 2009, 08:30

Yes but still, the powerjet is for unleaded fuel. It is useless for running leaded. Stick to a 95-96 and you will get better results.

Why is a powerjet useless for leaded fuel ?

k14

11th November 2009, 09:50

Why is a powerjet useless for leaded fuel ?
The whole carb was re-engineered to run unleaded petrol. The powerjet stops mid rev detonation which unleaded fuel is very bad at causing. The standard powerjet on a rs125 runs from around (I don't have my manual with me, will check when i get home) 8000rpm to whatever cut off you program it to do, there are 4 different cut offs which are selectable with different plugs into the loom. I think standard is 12600 and they go up in 200rpm steps from there. It also has a throttle position sensor that complicates things more in regards to on/off of powerjet. The way I understand it is that the way powerjet works is totally detrimental to achieving a good fuel mixture across the whole throttle range. You can perfect the fueling with the standard jetting configuration and because of the leaded fuel not have to worry about mid throttle opening/rev detonation.

The powerjet wasn't bought in till 1998, they changed the bikes to unleaded in 1997. You can still get leaded kits for the 125s and with them come a standard non-powerjet carb and 96 (or a kit) loom.

TZ350

11th November 2009, 17:10

.

Well this is a cockup...:laugh:...and won't be seen at Taupo, too wide, it sticks out wider than my feet.....:Oops:

But it sure looked the business, probably the Worlds first ever Suzuki GP125 fitted with an RS125 38mm carb.

.

Buckets4Me

11th November 2009, 17:30

you just need a nylon plug for the end of it and no nead for sliders that side :woohoo:

TZ350

11th November 2009, 18:00

This is the homologation document for the ibea L6 carb as used for the kf2 kart class.
http:www.j3competition.com/downloads/technical/L6_Homologation.pdf

You can see that it opens out from the 24mm choke to 28mm at the exit.

Thanks Sonic_V that's very usefull, now we know we are on the right track, just getting it all to fit is the problem.......

.

TZ350

11th November 2009, 18:02

you just need a nylon plug for the end of it and no nead for sliders that side :woohoo:

I'll put a nylon plug in your end........:bash:

Given up on that big carb idea, but have a much more devilish........:devil2:......plan

but will probably not be able to get it done before Taupo....:cry:...

.

sonic_v

12th November 2009, 01:52

I'm not too sure I would subscribe to the idea that a Kartsport engine spends little time in the peak power range there Sonic.

I am of the opinion that it is quite the opposite actaully!

One of the many things a Kart does well is hold it's corner speed!

You are just plain wrong on this one SS.

On a typical kart track the karts are geared for 65mph at the top revs - 20,000 rpm. Now as at most the peak power is at 13,000 rpm, this equates to a speed of 42 mph. The engines are well into their power by 10,000 rpm ie 32 mph. As karts can corner so fast and have high exit speeds they exit just about all the corners in the power band and because the gearing is so low they absolutely rocket out of corners.
By the time the kart is 30yds down the straight the revs are already well beyond peak power speed. At high revs (beyond 15,000) these engines are producing very low bmep and are only making a reasonable amount of power due to the high revs.

It is equivalent to riding an rs125 honda race bike in only first gear whilst being geared for 42 mph at peak power and then just holding the throttle and letting the engine rev for ever.

PS I was a 100cc kart racer for many years.

sonic_v

12th November 2009, 02:40

I am pretty sure that most "fixed gear" Kartsport engines run around 1.25:1, for the very reason that a longer spread of peak power is desireable.

100cc Kart engines typically have crankcase compressions in the 1.40:1 region.

I realise that some Kart engines are very particular about set up (I have minimal experience with these), but i have never heard of a moder 2 stroke engine that revs 7000 RPM over it"s peak power, and has a static curve.

Why would a 2 stroke engine that revs to 20,000 RPM have high advance, when the peak pressure point at 20,000 RPM come a lot sooner that at 14,000 RPM?

The 100cc rules have always stipulated a fixed ignition.

Who says peak pressure comes sooner at 20,000 rpm?

It does not come sooner if your charging efficiency is well down compared to the peak power speed conditions. Also the cylinder is being poorly scavenged resulting in a high residual trapped exhaust gas content. This slows up the combustion rate.

TZ350

13th November 2009, 17:11

.

Number two motor is ready to start going back together.

Pic-1 shows the big inlet port and the small roll pins that will accurately locate the copper spacer plates and under barrel fins. The mouth of the inlet port is built up with DevCon to direct the incoming charge up and over the flywheels.

Pic-2 shows the shortened cylinder studs and alloy TZ head bolts that I hope will expand at the same rate as the barrel and thereby reduce cylinder distortion.

Pic-3 the shortened studs will make it easier when the motor is in the frame to remove the cylinder head without scratching the gasket surface, which happened with the old long studs that protruded from the top of the barrel.

.

TZ350

13th November 2009, 20:50

.

Given up on the big carb idea, but could this work? a 24mm carb feeding into a plenum chamber and the 34mm rotary valve inlet feeding directly from the chamber to the motor. That way when the motor takes a gulp (duration 200 deg) it sucks full atmospheric pressure through a high flow 34mm bell-mouth and the restrictive 24mm carb has much more time (duration 360 deg) to refill the plenum.

.

TZ350

13th November 2009, 21:10

.

Where we have got to after 100 pages.

GP125 18+ rwhp: skim the barrel 1.5mm and “o” ring it, thin alloy spacer plate under the barrel and Suzuki RG250 pipe. Ex opens 86 deg ATDC and Trans opens 114 ATDC, std head , inlet timing 145/55 and carb mj 95.

GP125 20+ rwhp: skim the barrel 1.5mm and “o” ring it, thin alloy Spacer plate under the barrel and Suzuki RG250 pipe modified to RM125 specs, KX80 ignition. Raise the exhaust to open 83 deg ATDC, and widen to 70% of the bore, cut 30 deg from the closing point of the rotary disk, so inlet opens 145 BTDC and closes 85 ATDC. Set the mj 105 and ignition timing, 26-28 BTDC using a dyno.

Pipe dimensions Suzuki RM125 B/C page 82 Bell. http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf

And a collection of the better links from the last few pages, more collections on pages 80 & 90

24mm carb for 30+ hp go-cart engines posted by Sonic_V
Carb-01 http://www.out2win.com/catalog/images/ibeal5.jpg
Carb-02 http://www.out2win.com/catalog/ibea.html
Carb-03 http://www.j3competition.com/downloads/technical/L6_Homologation.pdf

Low loss venture tubes: http://www.cranemfginc.com/PDF/Venturi%202009%20CATALOG-2.pdf thanks Bucketracer

Save the stuffing around and go buy one of these digital, programmable ignitions
http://www.ignitech.cz/english/aindex.htm originally posted by K14

Expansion Chamber Design According to Blair:- http://members.bellatlantic.net/~vze2p5sj/modelengines/expcham.htm

This http://www.geocities.com/a57ngel/moto/CDI.html talks about repairing/modifying a KDX CDI's retard curve, there is also a schematic.

We see that the flow bends upwards and forward towards the exhaust port as the cycle proceeds and the piston rises to shut the port, taken from http://www.lortim.demon.co.uk/vsih/pistons.htm

If you want to plan your ports using Jennings or Blairs methodology then this very good and inexpensive software is just the ticket. http://www.porting-programs.com/ makes it very easy to get the true total and mean port areas of the transfers.

Some handy hints on making cables:- http://www.dansmc.com/solder_cable.htm posted by Bucketracer

It might be a 12A Rotary exhaust port but there is some interesting ideas about testing and port radiusing applicable to 2-stroke exhaust port shaping. http://www.yawpower.com/Flow%20Testing.html

Using a venture instead of a throttle plate in the carburetor to controle engine speed...........
Venture throttle:- http://www.prvperformance.com/PRV_induction_technical_overview.pdf

Another interesting pipe design program:- http://www.mh-aerotools.de/airfoils/javapipe_en.htm

Here is a xls spread sheet that can be downloaded that is based on MacDizzys work and covers blowdown time area:- www.essjayar.com/motorbikes/2_stroke.xls

Its a bit wordy but has some interesting ideas on getting ignitions going and lights if you need them. http://www.btinternet.com/~jhpart/bkns125a.htm

.

koba

13th November 2009, 22:49

Woop Woop! :woohoo:

Celebrating 100 pages!

gav

13th November 2009, 23:05

After 100 pages would've thought he'd have an FXR150 by now and save all the stress .... :innocent:

bucketracer

14th November 2009, 09:29

After 100 pages would've thought he'd have an FXR150 by now and save all the stress .... :innocent:

I think good old TeeZee (Dad) still dreams of two-stroke glory,

If he had brought an FXR150 he would have been able to watch a lot more TV. :zzzz:

Mow the lawns more often.......:done:

Do the shopping.........:scooter:

Spend time with the grand kids.......:chase:

Finish that second degree he started.....:hitcher:

Watch more of those interesting art house movies he likes......:corn:

Play solo in a friends aging punk rock band.......:violin:

Tell his wider group of friends, and especially the motorcycle ones how much he loves and enjoys them......:mobile:

.

bucketracer

14th November 2009, 15:35

.

Suzuki GP125 parts micro fiche and other things GP
http://www.cmsnl.com/suzuki-gp125-1978-uc_model13393/partslist/

.

Buckets4Me

15th November 2009, 07:39

I think good old TeeZee (Dad) still dreams of two-stroke glory,

If he had brought an FXR150 he would have been able to watch a lot more TV. :zzzz:

Spend time with the grand kids.......:chase:

Tell his wider group of friends, and especially the motorcycle ones how much he loves and enjoys them......:mobile:

.

he spends lots of time with the grandkids every month (now push the bucket faster this time) :bleh:

and he has made a wider group of motorbike friends (in the bucket community):jerry:

see you all at Mt Wellington

Yow Ling

16th November 2009, 11:06

OK Ive got myself a bit confused with this Carankcase compression thing. What is high and whats low. Say for example you had a crank case of 100cc and a displacment of 100cc that would be 1:1 Is that high or low? now say you had a crank case of 150cc and a displacment of 100cc 1:1.5? the number sounds higher but the compression will be lower.

Im sure somebody can sum this up in 1 line (please)

sonic_v

16th November 2009, 11:57

crankase compression ratio = CV / (CV - SV)

CV : crankcase volume with piston at tdc
SV : swept volume of piston

TZ350

16th November 2009, 18:35

crankase compression ratio = CV / (CV - SV)

CV : crankcase volume with piston at tdc
SV : swept volume of piston

Putting values to Sonic_V's formula:-

For:- CV = 300cc and SV = 100cc........300/(300-100) = 300/200 = 1.50:1 High......peak power, narrow power band

For:- CV = 350cc and SV = 100cc........350/(350-100) = 350/250 = 1.40:1 Med

For:- CV = 380cc and SV = 100cc........380/(380-100) = 380/280 = 1.33:1 Low......broad range, drivability

And as I understand it the common ratio range is something like 1.3 to 1.5

and the terms High, Med, Low, peak and broad range are all a bit arbitrary.

Chambers

17th November 2009, 17:39

.

If you want to plan your ports using Jennings or Blairs methodology then this very good and inexpensive software is just the ticket. http://www.porting-programs.com/ makes it very easy to get the true total and mean port areas of the transfers.

.

Used TeeZee’s software to plan my new engine for Taupo. The software can work with either Jennings or Blairs formulas.

Picture 1, is the screen for determining port heights and durations and port time area for the power you want.

Picture 2, is the cad section where you plan your ports to get the required port time area.

Picture 3, the software prints out all the data and a pattern of the new ports.

Picture 4, from the port cad printout I made a metal template of the port shapes.

Picture 5, with the template in the bore its easy to cut the ports to the right shape and the metal template also protects the bore from accidental slips with the Dreammel.

Bet TZ wishes he had thought of making a protective metal template when he did his barrel….:bleh:.... great software, thanks TZ.

.

F5 Dave

18th November 2009, 14:28

As a sidetrack,

These 2 pictures arrived today, I'm not 100% sure, but the cylinders are off a Yamaha from the early eighties belonging either to Johler Harald or Emmerich Stenger.

Evidently this engine was (apparently) faster than Anton Mang's Kwaka, but I havn't seen any evidence of that.

I imagine that ring life would be somewhat "short".

There are some pretty harsh marks on the bore directly above the transfers, I would surmise that is due to the "boost channels".

I'm 100% sure that it would have any gains, but it seems it may have.

I wonder if Boysen started off with this concept before ending up with the transfer boost's we know today?

Well back to this sidetrack from a month ago. (Page 95 for SS's pic) I've finally gotten to reading this Yamaha book (I got sidetracked by Kevin Cameron's TDC vol 1) ok I'm only just past first couple of chapters but there was a bit that went on fairly accurately describing this type of gullery port curving around the inlet (from memory) ". . . this type of port was first seen in the US in 1966. . ." on the Yam TD1 racers.

They were aircooled & the claim was it did help with sm.end oiling along with some piston holes as well.

Being watercooled & paired & piston port I still believe these were TZ500. Any thoughts on this?