ESE's works engine tuner

[wobbly]

OK , so its easy to cut the seams on a stock pipe , open it and rework it internaly , then reweld it back together to appear exactly as stock.
This has been done plenty of times , one example being the Stock classes in World Champ Jetskis and Karts , I have reworked many , and they are still winning titles.

[husaberg]

OK , so its easy to cut the seams on a stock pipe , open it and rework it internaly , then reweld it back together to appear exactly as stock.
This has been done plenty of times , one example being the Stock classes in World Champ Jetskis and Karts , I have reworked many , and they are still winning titles.

the way i read it its only the p class A that runs stock exhaust.....?

[F5 Dave]

"OEM displacement specifications
must remain stock. "

Hmm, trying to find something that hasn't been rebored might be a big ask.

Unmodified chassis parts. Wonder how literally they apply the position of those parts? Principally the front mudguard and suspension travel. . .
Can you find a YZ100?

[FJRider]

"OEM displacement specifications
must remain stock. "

Hmm, trying to find something that hasn't been rebored might be a big ask.

Many moons ago I got involved in racing Mini 7's ... similar regulations were applied to the class. The best (legal) gain in performance was to "Blueprint" the engine ... which is to build the engine to the exact spec's and tolerances ... the engine designer originally specified for production of the parts and assembly of the engine.

[husaberg]

"OEM displacement specifications
must remain stock. "

Hmm, trying to find something that hasn't been rebored might be a big ask.

Unmodified chassis parts. Wonder how literally they apply the position of those parts? Principally the front mudguard and suspension travel. . .
Can you find a YZ100?

later on for most vintage class's it says 50 thou overbore which is 1.25mm?
As long as it remains under class.
oem spec allows for in most cases 1mm.
That said, a MB100 is over the allowable size on a .25mm overbore

[Roflhat]

Rules are fairly limiting, allowed to change tires, handlebars within reason and airbox element. I've already had the exhaust apart and welded in a cone then covered up again. Changing the exhaust will change the frame class
Also took the foam out of the seat and replaced with softer stuff, so it looks stock but when I sit on it I'll be about 1.5" lower

[pete376403]

Many moons ago I got involved in racing Mini 7's ... similar regulations were applied to the class. The best (legal) gain in performance was to "Blueprint" the engine ... which is to build the engine to the exact spec's and tolerances ... the engine designer originally specified for production of the parts and assembly of the engine.

I assisted a guy with his 7 way back when as well. There were blueprinted engines and there were "blueprinted" engines. A bit like paraphrasing George Orwell - "all engines are equal, but some engines are more equal than others". A good reason for the AMA claiming rule, that has been applied to other classes as well. Up to 30 minutes after the end of a race, any competitor in that race can claim the winners engine for a predetermined sum - deters people from spending astronomical sums on an engine that might end up going to someone else for 10 grand or something.

[Frits Overmars]

We do quite a bit of work on our cranks. Big End pin bored to 22mm, std stroke for the air cooled's or de stroked for the 110's, alloy plugs in the counter balance holes, Mallory plugs for correcting the balance factor to 50% and inside faces machined back for extra crankcase volume (extra volume works best with a very sucky pipe).

Apart from enlarging the crankcase volume, which indeed requires a sucky pipe to make the most of it, machining the inside faces back for extra crankcase volume has yet another advantage: it improves lubricating and cooling of the big end bearing.

I noticed a couple of things in your crankshaft picture though. As a rule of thumb you'll need at least half the big end pin's diameter worth of material around the pin bore for a firm grip on the pin. My MS-Paint analysis may not be exact, but 7 millimeter of material around the bore doesn't look bulletproof to me...

The Mallory balance plug will need a small amount of shrinkage fitting, which brings a tension load in the material around the bore. And when you rev it, centrifugal force will increase this load. Again my analysis may not be exact, but only 1,5 millimeter of material around the bore doesn't look bulletproof either...

The rules say nothing about keeping the original pipe ?????

PRODUCTION (P) CLASSA “production motorcycle class” is as “produced by a recognizedmanufacturer”, and the public must be able to purchase a minimumof 500 frames through retail dealers. Production class motorcyclesshall not be modified from Original Equipment at time ofmanufacture. e.g., frame, forks, gas and oil tanks, seat, front andrear lighting, fenders, wheels, brakes, air intake box and(unmodified) exhaust system.

OK , so its easy to cut the seams on a stock pipe , open it and rework it internaly , then reweld it back together to appear exactly as stock.

That's called cheating Wob. After a lifetime of composing rulebooks and dodging other people's rules, let me tell you how to read them. You'll need an unmodified exhaust system. OK. But if it doesn't say from which bike, you could use an RSA pipe if it happened to fit the bike without modifying, and if you could find and afford one. Simple as that.

And while I'm here: Happy New Year everybody

[andreas]

Right back, Frits

[FJRider]

I assisted a guy with his 7 way back when as well. There were blueprinted engines and there were "blueprinted" engines. A bit like paraphrasing George Orwell - "all engines are equal, but some engines are more equal than others". A good reason for the AMA claiming rule, that has been applied to other classes as well. Up to 30 minutes after the end of a race, any competitor in that race can claim the winners engine for a predetermined sum - deters people from spending astronomical sums on an engine that might end up going to someone else for 10 grand or something.

There were a few that spent money that was beyond the usual ... I think to compensate for their lack of ability in the drivers seat.

Those were times mini when engines were in abundance. We didn't have the money for constant expensive (to us) rebuilds.

We won a few races ... and had a bloody lot of fun. The actual base reason for these types of racing to have started.

On a few occasions ... I gave a whole different meaning to the term "Angle Parking" ...

[Ocean1]

Many moons ago I got involved in racing Mini 7's ... similar regulations were applied to the class. The best (legal) gain in performance was to "Blueprint" the engine ... which is to build the engine to the exact spec's and tolerances ... the engine designer originally specified for production of the parts and assembly of the engine.

Of note with the final iteration of those reg's was the simple expediency of defining what you WERE allowed to do.

I recall previous attempts, particularly banning grinding off the massive vertical body seams and welding the joints up properly.

[FJRider]

Of note with the final iteration of those reg's was the simple expediency of defining what you WERE allowed to do.

I recall previous attempts, particularly banning grinding off the massive vertical body seams and welding the joints up properly.

The cheaper course of action was using superior driving skills ... or taking advantage of the other drivers lack of skill.


Or as in most cases (when getting a win) ... just hope you get lucky.

[TZ350]

We started with the original Suzuki GP125 air cooled cylinders and by taking the exhaust port timing and port width to extreme's.
We managed 31 RWHP on our best dyno day. But the engine faded with heat stroke quite quickly on the track. So we looked to water cooling.
Class rules required reduced capacity for water cooled engines.



Suzuki GP100 with replated NSR water cooled cylinder and de stroked crank for 110cc.

Standard NSR cylinders gave about 26 - 28 RWHP and a heavily ported one to the air cooled specs was 29 - 30 RWHP.
Disappointing results from the NSR cylinders that have lots of lovely ports that look pretty much like the Honda NF4 RS125 race cylinder.
We were clearly getting better transfer and trapping efficiency with the ported air cooled Suzuki GP125 cylinders than we could manage with the Honda NSR one's.

The take away here is that the pretty looking ports of the NSR cylinders did not translate to better performance.



In reality NF4's make way more power than our GP's. So something is wrong. We got hold of a NF4 engine to take a quick look at the port timings.

NF4.

NF4
Ex opens nominally 84 ATDC for 192 degrees duration.
A Transfers open 115 ATDC for 130 duration.
B Transfers open 117 ATDC for 126 duration.
C Transfer opens 122 ATDC for 116 duration.

30 RWHP Air Cooled GP125 cylinder.
Ex opens nominally 80 ATDC for 200 degrees duration and 72% bore width.
A Transfers open 114 ATDC for 132 duration.
B Transfers open 114 ATDC for 132 duration.
C Transfer opens 114 ATDC for 132 duration.

The Exhaust port time area shape is a little more generous on the NF4 cylinder than the NSR one but other wise pretty much the same timing.

The interesting difference is between the more powerful NF4 Ex at 192 duration and the single Exhaust port 30 RWHP Suzuki GP at 200 degrees duration.

The shorter NF4 exhaust duration of 192 has expansion chamber resonance benefits.

I think we may have been over porting our NSR cylinders by making them similar timing to our best air cooled cylinders. Looks like we should try one made to more closely replicate the NF4 cylinder. Match the NSR's blow down time area to the Suzuki air cooled cylinder.

By being lees ambitious with the NSR's Exhaust duration we may get better results with improved pipe resonance.

[wobbly]

The NF4 MX bike case based cylinders have been hugely surpassed in performance with dozens of updates from the factory as well as examples from other manufactureres, using 54.5/54
The transfer stagger numbers are super old school and can be easily updated to something more modern that would make way more power everywhere.
My first thought that needs an STA check of course would be near 114-116-117 with an Ex around 83 to 82.5 as later customer engines came with..
And as for having all the aircooled transfers @ 114 , that is simply Hp suicide from mid last century as conventional stagger is super effective in widening the powerband in non PV cylinders.

[TZ350]

My first thought that needs an STA check of course would be near 114-116-117 with an Ex around 83 to 82.5

Thanks Wob. I just need to check. Is that 114-116-117 port A-B-C in that order.