ESE's works engine tuner

[TZ350]

Is that Roffe that Swede of MB50 disk valve Derbi cylinder fame?

http://translate.google.co.nz/transl...26prmd%3Dimvns

Attachment 249742Attachment 249743Attachment 249744

Dont know, but here is his fan club.........

[TZ350]

Tec posts for Page 350 (but not complete yet)

Speedpro has won the race to be the first documented useful Bucket engine at 30rwhp

the powerjet switched with a solenoid is done just after peak power,as the engine is most efficient at peak torque,where it needs the most fuel.
But the carb doesnt know about efficiency, only bulk flow past the main jet - and the flow keeps rising as do the revs,so the mixture goes rich over the pipe ( thus reducing the temp).
By switching off some of the orifice area ( PWM is way better) we can lean down the fuel curve into the overev and heat the pipe up way more than is possible at peak torque.
On a HRC - RS250 for example the solenoids are activated at 12200 to 12800 ( adjustable plugs in the loom) and it will rev hard to 14000.
Without the powerjets it falls dead just past peak power at 12000.

STA or Specific Time Area, (Port Time Area) is at the heart of 2-Stroke port timing design. For what its worth and as I understand it. How to determine the STA numbers

To get around 38 crank Hp from an RGV100 ( to create mid 30RWHp) the T port needs to be up at 198 duration.
This is governed entirely by the blowdown available when the transfers are in the right place as well.
Having the T port as well as the aux ports may allow the exhaust port to be dropped a few degrees in duration,this then increases the range where the pipe is in resonance,giving a wider spread and no drop in peak power.
I need to measure one up though to see what is possible when it is sleeved back from the 56 bore to 50mm Edit, its 54 bore,so has a stroke of 54.5 unlike the earlyer engines.

"MSV is high at 25M/Sec", forget all that old shit - here is the go with squish.
In any race engine the squish height should be set at the minimum achievable,just shy of the piston tapping the head when overeved.
In a bucket where the norm is "only" 13000 there is no reason to have any more than 0.6mm.
The squish width based on MSV is a theoretical number of little relevance when we are running the piston in the powerband just short of hitting the head.
But with a parrallel squish ( ie curved same as piston dome rad - or a straight cut with minimal divergence) then in most cases we can use 40 to 45% squish area.
This generates MSV numbers in the high 30 M/Sec region.It has been stated in a few references that " high"squish velocity will bump up mid power and reduce the top end.
Yes, in a limited view of things it does.But now that we have digital programmable ignitions thats rubbish.
The high MSV increases turbulence in the end gases, this increases flame speed, and has the same effect as high com or too much advance.
Simply retard the timing and the rpm comes back, but you keep the power generated by better turbulence burning up more of the end gas trapped in the squish.

One point to remember is that the best radius on the squish corner into the bowl is no radius at all.A sharp corner with just with a rub of sandpaper to get rid of the ragged knife edge, works best.
And with any of the race type plugs we are using approx 1mm of unthreaded plug end should be protruding into the chamber.
The old B10EGV was originally designed to be used this way by NGK, but nowdays the trick plug is a R7376-10, this plug makes more power than any other tested with around +2 Hp better than an expensive Denso equivalent, here is the test i have shown before.

I haven't read the entire thread - I doubt anyone could - but balance factor discussion caught my eye.
The "conventional" factor of 50% plus works on upright cylinders - it makes them shake in the plane of the cylinder, ie up and down...this is generally the preferred direction as most frames are capable of damping vibrations in ths plane.
On horizontal cylinders an inverse balance factor is used. 25 - 28% works very well.This will make the motor shake at right angles to the plane of the cylinder...ie the preferred "up and down" direction...
FWIW I understand that parallel twin TZ's were around 33%....angled cylinders do make a difference. It ain't simple....

From the twostrokeshop

I don't want to lapse into too much tech-babble here; suffice to say, a crank that is 'under-balanced', such as the YPVS/Banshee crank, tends to create oscillations/vibrations in the vertical plane. This, for anyone who has ever converted an LC or YPVS 250 to a 350, is exactly the type of stronger vibrations you feel when switching from the 250 to the 350.

A crank's Balance Factor is typically expressed as a percentage figure. Normally the balance factor on a twin such as the RD is set at 50% to 55% of the total reciprocating mass - in this case 342g - so this would need 171g for the 50% case and 188g for the 55% case.

More on crank balance here. http://www.twostrokeshop.com/RZRD350...fts.htm#sermon

Interesting look at TZ cranks. http://www.twostrokeshop.com/RZRD350...rankshafts.htm

And the different wear results of different B/E brg cages. http://www.twostrokeshop.com/peek_co...nd_bearing.htm

All that balance stuff on the Twostrokeshop site I did 3 years ago when starting the TSS500 project.
I was amazed when checking the RZ balance factors,and then found that someone at Yamaha also did it properly when designing the RD400, as it is set at 55% in both the drilled and leaded crank versions.
The stroker cranks I have for the RZ/LC all have Peek big ends,with Mallory balance weights,and I have the roller mains in stock.
The roller mains do have slightly more friction but will handle over twice the loading
,and last forever.
No one has tried Peek on the small ends as far as I know - but I have special silver plated small end bearings for the RZ/LC/Banshee.

The 90* crank versions I built for the TSS500 was an embarrassing nightmare.
The crank force simulation shows 31% less rocking couple and way less forces on the mains.
The first one I tested was absolutely fine vibration wise,but in reality it had,by shear chance an unbalanced prototype flywheel on it.
The two pistons rising to TDC close together create a vertical shake that vibes the bars like hell.
This can be offset by creating an opposite force in the flywheel,as I tested this by clamping a hose clip onto the ignition,with the screw positioned 1/2 way opposite between the two pistons at TDC.
But this "fix" creates a huge rotating out of balance force on one end of the crank - and the RZ case has enough trouble maintaining main bearing crush on a balanced assembly, without pounding it to death running an out of balance flywheel.
The carbs and bars vibrate enough to froth the fuel without soft manifolds - so the idea was dropped ( on my head).

Lots of interesting links on Husabergs original post

Balance with The hose clip innovative. These three engines I used were went to be like jackhamers until they were timed to fire as a single I have no idea why they ran smoother firing as a single I will try and find the articles as to why but I guess they didn't know why either other than the rocking.I understand it makes no sense.
In a single couldn't a narrow single couldn't experiments be carried out for balance factors on the ignition rotor as wobbly did. I am picturing something light a stealthy flywheel weight bolted on might not work on a a inner rotor type.
Attached is the Irving article on a 76 degree firing parallel twin crankshaft.

below is a exert from flashback fabrications on a Aemacchi Single balance.

This stuff relates to balance factors differing according to the frame thay are in.I do note the Commando and the Atlas were very much the same engine but the Commando is rubber mounted in its std frame and on a 20 odd degree angle in its std frame.

That's something lots of people don't understand. The huge forces don't go away, they are opposed, sometimes within the crank assembly and sometimes by a seperate rotating assembly. BMW of course used a seperate reciprocating assembly. The crank assembly counters reciprocating forces in one direction only and when there isn't any reciprocating force to counteract, at 90 degrees, it actually introduces an unopposed force. If a seperate rotating assembly is used for counterbalance then all the forces act through the crankcases and they can be large. The actual forces on bearings caused by the production of power are insignificant compared to the forces created by the movement of the parts whether reciprocating of rotating.
Any 90 degree engine with an even number of cylinders is great for this problem as there is forces acting at 90 degrees which balance out just sweet.

There is lots of interesting views and pictures of crank balance posted on the following pages …….

Here is the 90* side of the story.Interesting.

http://www.xs650.org.au/smoothness.htm

I think someone has posted this before, but I couldn't find it so here it is again.

http://www.saltmine.org.uk/shoeman/shoeman.html

Interesting read about tuning RD's.

MAHLE engine failure manual

http://www.mahle.com/C12572E60048082...5ULLE756STULEN

Copper coating the rod or crank areas not needed to be hard, prevents the heat treat process from affecting the core - leaving it more ductile and crack resistant.
The company Heat Treatments have a paint on product that does the same job.

Bottom line is that when tuned for max power the disc valve does make more than a reed - those flapper things are always "in the way" to some extent..
But there are many trade offs.The disc will have NO power at all under the tuned for range, as it cannot suppress reversion at low rpm, and you cannot tune out the fact that the intake waves are telling the main jet signal all manner of lies,repeatedly.
Thus a reed engine can have much wilder exhaust timing and pipe design without giving away a heap of "under the pipe" power, and this exhaust tuning can have plenty of overev power as well, if that's what is needed.
An example would be the pipes I did for the fastest,and record breaking Honda RS250 on the salt last year, it had over 90RWHp between 12000 and nearly 15000,so would simply keep revving till the aero drag stopped it.
The peak power was "only" 96 I think, but it had plenty everywhere else it was needed.
To get that sort of overev power from the RV would mean it would be all but impossible to get it to carburate off the pipe, as the closing timing needed to get to 15000 would be mentally wild ( like 98*+ ).
And the last thing to consider is that despite what the supremely clever Frits and Jan say and did - in the last year of 250GP a Honda reed valve engine kicked Aprillias arse in the title - with a guy who cant ride a MotoGP bike to save himself.
The newer RSA engine is probably an unbeatable combination in 125GP, but for many other less demanding applications the reed has real, and useable, advantages.

With todays technology the bar can now be raised to around 40 crank Hp without too much drama involved, and thus achieving around 35 RWHp.
Its just a matter of careful parts selection and very careful assembly.

The alloy inserts for the TZ350 was the customers choice - once its all proven, and we get a handle on what the engine likes, then I will do some bronze ones.

AvGas in NZ is all LL100, this is low lead 100 octain.But the rating is defined differently in avaition.Its approx equiv to 100 "pump" gas, but has a lean rating of 100 and a rich rating of 130.
MNZ Appendix E defines avgas as max 112 MON amd max 108 RON.

Avgas, or any leaded "race" fuel reacts completely differently to unleaded pump gas.
In general terms the unleaded hates compression, but loves timing.Avgas is the opposite in that it makes more power up to the knock limit with more com.
Unleaded makes better power when run rich,avgas makes more the leaner you go.
Tuning in the old days with RS and TZ engines meant using lean mains and small powerjets ( 35 ) as turning off a big jet over the top would mean being too lean in the overev.
Nowdays the unleaded fuel runs rich at peak power, then uses a big powerjet ( 55) to create some heat in the pipe over the top.

Race gas bought in drums really is" low lead race gas", nothing wrong with it - but hard to get the same stuff in many places.
The stuff in tanks at stations/tracks is "old" avgas.The best, and only way to be sure of what you are getting is to go to any local airport and buy Avgas - it is tested regularly and is guaranteed to be fresh and to spec - has to be, or the Lycomings would all fall out of the air - bad.

Having multi cone sections gives the designer the ability to shape the power curve to the desired application.
Add to this 2 stage headers and you can achieve any wave amplitude correction needed with a 3 stage diffuser.
Here is a design I did for a Euro champ winning 50cc Malossi,it has a nozzle in the exhaust duct with an oval to round transition in the flange.
A two stage header, 3 stage diffuser with the steepest angle in the middle.
A killer pipe for the cylinder porting as it was used for long track racing only.
Graph is crank Hp

Pumpers are pretty easy to suss.
The pop off pressure simply sets the amount of fuel passed up to 1/2 throttle, transition from closed throttle,and around idle.
This should be set such that the bottom jet is no more than 2 1/2 turns out for the correct fuelling in the bottom end.
The pop pressure should be set with the needle and seat wet, and should hold its set pressure right up to the point of blowoff.
The top jet sets the fuelling past 1/2 throttle and mainly affects the ratio delivered at peak and beyond.
This should be less than a turn.
The pop off lever height sets the overall amount of fuel able to be delivered, the higher the lever the sooner, and further the needle is pushed off the seat, allowing more fuel to pass to the jets in total.

Re the lever arm height on the pumper - the free end should be set such that the middle of the arms end thickness is flush with the floor of the body.
Some say the top of the arm flush with the body floor, but most tuners raise this a little to 1/2 the thickness.

TeeZee some pumper carb tuning tips to go with Wobblys info. Attachment 247635

And here is something if we really cock it up..... ...... piston seizures explained Attachment 247636

One thing I completely disagree with in the piston seizure write up is that air leaks cause a lean condition.
This is utter bollocks, any engine with a case leak will run richer, the bigger the leak the richer it will run.
Caused by the fact that the case "pump" no longer works and the fuel air mixture isn’t being transferred thru the ducts.
If the engine is then leaned up to "fix" the incorrect mixture - then it seizes.

A leak between the carb and the reed or any intake will always add air going into the engine and create a lean condition.
A leak anywhere in the case, be it a gasket, a seal, or a pin hole in a casting will cause the engine to run rich.
Problem is that they then seize for no apparent reason when the jetting is then "fixed".
So its always wise to make a set of blanking plates and or use a rubber bung with a bolt that expands it into the pipe manifold, so that a leak down test can ensure no case problems exist.

Piston specs here inc ring peg locations
http://www.pvlsverige.se/vrm/kolvar/kolvar.html

This is real Gold

Small problem you have overlooked with that piston.
Its only 50mm long and with a 100cc bucket we are usually using the 50.6 stroke cranks, thus the exhaust port will be exposed to the case when the piston is at TDC, unless you raise the port floor.
The 1.2mm ring is too wide to be running over 14000 rpm as well, and the huge hole they have around the pin will create port linking issues with a wide T port or a big 3 port setup.
The 50mm oversize RM85 pistons I got are 51mm long, just enough to work OK, as are the 50.5mm CR85 +3mm ones for Mikes engine.
Also the TM carb is an old design, one of the first semi flat slide carbs - the later TMX and PWK types flow alot more air due to much superior slide shape.

Effects of changing compression ratios, complete with dyno graph.

Dialled it in best we could with ignition and jetting but suspected it was a bit over compressed so we put a gauge on it, 195psi cranking, Blue line.

Interesting to see how the power changed with compression.

Everyone uses the chamfered pin with plain clip now - but for years we had to cut the inner leg off TZ clips and add the chamfer to prevent the clips from popping out.
Dont know if Irving was the instigator of the idea, but it works a treat.

Primary com of 1.37 would be about right for the average transfer duct and port geometry being run.
If the descending piston compresses the volume, then its part of the case compression if its connected when the piston port is closed.

I think this is one of the big ideas that have come from the work on the flow bench. You need to look at the whole post and pictures, the idea is that a small deliberate step gives better flow than a perfect match.

TeeZees carb with a small even 0.5mm step all around the edge will make it easy to take off and refit without loosing any air flow at the joint through any slight miss alignment.

You need to read the whole post for Wobblys thoughts on Com Ratio.

As Avgas is allowed, and we are discussing small bore race engines with sub optimal ports/pipes etc then I would say around 15.8 would work fine.
On pump gas, be it 91/95 or crap 98 then reduce this to 13.8 and wind in lots of static advance.
Avgas isnt created for what we are doing, but its cheap enough,available at any airport,and works real well when pushed to the edge of the tuning envelope.
The other issue is that to be effective, the squish clearance should be just above what would give zero clearance in an overev situation.
Thus any 50 or 100 cc bucket is able to run down at 0.6mm with complete safety, without running into issues of excessive squish velocity, unless you are well over 50% SAR.
But dont give me any grief when the thing melts using an 8 plug when any engine making any power at all, should have a 10 iridium as a baseline.

Sorry my mistake - I was referencing to water-cooled numbers.
For air - cooled, take one ratio less in both cases,ie 15.8 down to 14.8, again as the small bore/displacement allows alot more leeway..

Compression ratios and what works …….. you need to go to the post.

Thanks for expanding on that ........

Current thinking in a road race setup would indicate 145/90 is the outer limits of whats needed so this could be tried, opening up one side at a time.

Just cracked open a Rotax 256 had 155/90 as the disc timing......... kart blokes bless em all

BMEP the gauge that allows the serious engine developer a direct way to compare different internal combustion engines, from lawn mower to massive prime movers.
2-T BMEP (psi) = HP x 6,500 / L x RPM
4-T BMEP (psi) = HP x 13,000 / L x RPM
where L = Litre and converting PSI to Bar is Bar = PSI x 0.069

Take the very best 125GP engine specs and plug that into the formula.
We have 50Hp times 6500 divided by 0.125 times 13000 = 200psi which is a real, usable number, I see all the time.
Use the same numbers for a 4T and we have 50 times 13000 divided by 0.125 times 13000 = 400psi , that is completely impossible, and this is the whole reason a 2T is superior to a 4T when compared apples for apples.

[bucketracer]

Buckets is not the only thing Team ESE gets up too.

Phillip Island Moto GP 2011



Chambers in the red hat talking with Rossi after his off, NedKellys just off screen.

Rossi would have been interested in Teaming up for the 2 Hour but his contract with Ducati won't let him.

and Chambers recons million dollar Ducatis fill up with dirt during a crash just like Buckets do.

Well maybe Chambers didn't actually talk with Rossi but that is Chambers in the red hat.

[husaberg]

Tec posts for Page 350 (but not complete yet)

When is someone/anyone going to write a modern two stroke tuning book? Well then!

Dont know, but here is his fan club.........

Phah Swedish girls. They kind of look a little plain compared to Kiwi Chicks. Like these below

http://www.google.co.nz/imgres?q=kiw...t:429,r:8,s:91

[Buckets4Me]

tada

[wobbly]

The author of the best 2T simulation software package available, and believe me I have used all of them including Fluent driven by Solid Models and full Cd mapping,
could not make a living out of selling his software.
I talked to him about doing a book, and including his software as a package, just like Blair did many years ago - that I thought was a godsend.
Read the book, then use the software to develop your engine.
There is no money in it at all, for the effort and costs involved in getting it to print.
Maybe sell it online, as a downloadable package,but again, the costs of setting up that scenario would mean questionable profitability.
Blair was a paid Prof, Neels van Neekerk the software author is a Head of Engineering Research, they have jobs to pay the bills.
The last Tech book that made any money was and is a Uni manual - Theory of Machines and Mechanisms, that I bought as it had a disc with engine balancing code on it.
Its author is Prof of Engineering at Uni of Wisconsin - Madison.
None of the traditional print houses is interested in tech manuals, even if Steven King were to do one.
At this point its up to you to buy the software and learn, but thats also hard in that crap in = crap out, so you have to then build crap to learn that it is - Catch 22, that made money.

[husaberg]

The author of the best 2T simulation software package available, and believe me I have used all of them including Fluent driven by Solid Models and full Cd mapping,
could not make a living out of selling his software.
I talked to him about doing a book, and including his software as a package, just like Blair did many years ago - that I thought was a godsend.
Read the book, then use the software to develop your engine.
There is no money in it at all, for the effort and costs involved in getting it to print.
Maybe sell it online, as a downloadable package,but again, the costs of setting up that scenario would mean questionable profitability.
Blair was a paid Prof, Neels van Neekerk the software author is a Head of Engineering Research, they have jobs to pay the bills.
The last Tech book that made any money was and is a Uni manual - Theory of Machines and Mechanisms, that I bought as it had a disc with engine balancing code on it.
Its author is Prof of Engineering at Uni of Wisconsin - Madison.
None of the traditional print houses is interested in tech manuals, even if Steven King were to do one.
At this point its up to you to buy the software and learn, but thats also hard in that crap in = crap out, so you have to then build crap to learn that it is - Catch 22, that made money.

Shame really.
Because Jennings is so 70's Bell is like so 80's Robinson is so early 90's
I suppose even if it was printed in electronic form, someone would just pirate it anyway.
After all the current 2 stroke tuners are gone it will probably just die (The 2 stroke)
Without Bell. I would have probably Just brought a diesel.

It would be interesting to run a simulation on say Bells RM125 road racer tuning example. This time with 2011 technology with a modern pipe design and modern tuning techniques to see just how far the 2 stroke has came in 30 year's since bell probably wrote the book.

What good is knowledge if it can't be shared. (It not a slight a you Wob you need to make a living and it's not easy being self employed)

Four stroke are just so boring. Honda basically done it all in the 60's. The 2 stroke as so much more to give.

For instance F5Dave made a comment regarding the lack of 2 strokes in the bucket field of the race that Mike had posted. The GM street race.
Well I sure as hell noticed the same thing.
I just added up the feild out of the program.

Out of 29 guess how many were 2 strokes.
11 no, 10 no. 9 no, 8 no. 7 no, 6 I wish.

I count 5. Yes only 5.
It could have been 4 shit. I am not sure about one of them, (Johnny Buchanan Honda G4)

It was, As always one of the bigger classes. In fact the biggest if you add in the fact the the larger classes were mixed capacities.






Exit soapbox Ning Ning



For Frits and Wob. How much difference do the carbon pipe covers and or pipe lagging that Aprillia and others used to run make HP wise in top end?
Is there still a place for them or has the electric solenoid PJ rendered them redundant?

[bucketracer]

[R RATED]When is someone/anyone going to write a modern two stroke tuning book? Well then!

This thread and others have a lot of info .........

[Frits Overmars]

This thread and others have a lot of info .........

I agree with Wobbly (I usually do): there is no money in paper books on two-stroke technology (there is little money in paper books period, unless you happen to write Harry Potter stories). But you'll find a lot of present-day info in forums.
ESE's works engine tuner is a good example, and of the numerous other forums that are 'open to the public' I would recommend www.pit-lane.biz. It's French-based, but yours truly and Jan Thiel are allowed to write in English (and I post all my photos in Dutch without anyone noticing).
A good starting point would be here: http://www.pit-lane.biz/t117p246-gp1...es-aprilia-rsa.

Reading through the above posts my eye fell on this remark from Wobbly, talking about reeds versus disks:

despite what the supremely clever Frits and Jan say and did - in the last year of 250GP Honda reed valve engine kicked Aprillias arse in the title - with a guy who cant ride a MotoGP bike to save himself.

First of all, thanks for the flowers, Wob (like I just said, I usually agree with mr. Wright).
Second: it should read Jan and Frits, not the other way round; Jan did much more than my humble self in making the two-stroke so suppreme that it had to be put down by the Honda-Dorna combination.
Third: I would not say that a Honda reed valve engine kicked Aprilias arse. The Aprilia riders did that all by themselves, stealing points from each other and shooting each other off. Not even Honda-driver Hiroshi Aoyama would dispute that the Aprilias were faster.

[Frits Overmars]

...For Frits and Wob. How much difference do the carbon pipe covers and or pipe lagging that Aprillia and others used to run make HP wise in top end? .....Is there still a place for them or has the electric solenoid PJ rendered them redundant?

"Is there still a place for them?" I should think so; look at the Aprilia RSA125. There the cover does two things: shield the pipe from a cold air stream, but more importantly, as you can tell by the shield covering only the top half of the pipe: shield the crankcase from radiated pipe heat.
How much difference? We can only guess (which I avoid as much as possible) because nobody ever took the trouble of measuring the difference on a real track (were measuring the power would not be simple anyhow). The crankcase-shielding will give more power everywhere and the pipe-heat conservation will give more overrun which is extremely import for lap times.

[Buddha#81:Me]

For instance F5Dave made a comment regarding the lack of 2 strokes in the bucket field of the race that Mike had posted. The GM street race.
Well I sure as hell noticed the same thing.
I just added up the feild out of the program.

Out of 29 guess how many were 2 strokes.
11 no, 10 no. 9 no, 8 no. 7 no, 6 I wish.

I count 5. Yes only 5.
It could have been 4 shit. I am not sure about one of them, (Johnny Buchanan Honda G4)

It was, As always one of the bigger classes. In fact the biggest if you add in the fact the the larger classes were mixed capacities.

Sorry man Johnny was on a GL145.......stink aye and 2/3rd of the field was fxr's or fxr powered......

[dmcca]

At this point its up to you to buy the software and learn, but thats also hard in that crap in = crap out, so you have to then build crap to learn that it is

Ive been using engmod2t for a little while now and initially though there were limitations in what it could do but now realise that i'm the real limitation... there are so many ways to measure and input data and its extremely hard to know if you're doing it right...

Im guessing the only way to tell is test with a dyno and compare results, then alter the way data is entered until dyno results consistently equal sim results...

Are there many engmod2t users on KB? might be worth starting a thread asking/answering questions.

[husaberg]

"Is there still a place for them?" I should think so; look at the Aprilia RSA125. There the cover does two things: shield the pipe from a cold air stream, but more importantly, as you can tell by the shield covering only the top half of the pipe: shield the crankcase from radiated pipe heat.
How much difference? We can only guess (which I avoid as much as possible) because nobody ever took the trouble of measuring the difference on a real track (were measuring the power would not be simple anyhow). The crankcase-shielding will give more power everywhere and the pipe-heat conservation will give more overrun which is extremely import for lap times.

Thanks Frits I had never considered the heat soak from the pipe to the Crankcase.

Given the bucket rules we run under AC 125cc with 24mm carbs and LC 100cc open carbs what would you go for.
The only 6 speed one is the Kawasaki in the Disk valve models and GP125 Suzuki with 5 basically all the reed valve ones Case or cylinder are 6 speed and We are not adverse to deboring or destroking a 125cc Later model engine.
I am thinking open race tracks here in the South Island. Sorry its a curly one.



Other question anyone no the firing order on a TZ750 I was reading something the other day that suggested the cylinders fired in Pairs the outer two and then the inner two together. If they do I wonder why? Was it because of the way the cranks were made and Joined?

[Frits Overmars]

I would stay away from air-cooled racing engines at all costs.Then again, I would find a way around the carb diameter limitation; take a look at www.pit-lane.biz where I explained the backgrounds of my 24/7 inlet system.

[husaberg]

I would stay away from air-cooled racing engines at all costs.Then again, I would find a way around the carb diameter limitation; take a look at www.pit-lane.biz where I explained the backgrounds of my 24/7 inlet system.

Awesome PG 13 found it. Interested to know what the Air cooled rear disk valve engine is around page 5 .