ESE's works engine tuner

[Roflhat]

Here’s what I’ve gone for, opened up the piston hole to match the port and elongated it. Lengthened the slot for the C port and I’m closing up the back of it which would go to the casing, going to smooth it off so it’s a nice curved shape. Piston hole is angled up into the port

[TZ350]

Here’s what I’ve gone for, opened up the piston hole to match the port and elongated it. Lengthened the slot for the C port and I’m closing up the back of it which would go to the casing, going to smooth it off so it’s a nice curved shape. Piston hole is angled up into the port

Yes, that looks good to me, so long as the hole in the piston is fully open at TDC and BDC.

Most of the "suck" from the pipe happens around BDC.

It is the pipes suction action that moves the bulk of the mixture up from the crankcase to the cylinder.

Then the reverse pressure wave returns some spilt mixture in the header back to the cylinder. Then it plugs the exhaust port, stopping the rising piston from spilling mixture out of the Ex port. A lot more complex interactions happen too but sucking then plugging is the basics.

Cutting metal to reflect the best of two stroke tuning theory is a real challenge.

I know there is plenty more time to be spent getting the engine and bike built. But I am really looking forward to seeing the dyno results then a report on how it went on the Salt.

[F5 Dave]

Hold on. Wasn't there talk of keeping the std pipe silhouette for class rules? If so then pipe action even if hidden under a std cover will be minimal. So crankcase stuffing and as many revs as possible will be only course of action . Unless I remember that bit incorrectly. I could wade back a few pages, but it appears I'm way too lazy for that.

But back to revs. Engineering is the 2 stroke tuners 1st port of call on classic engines. You need a rod capable of crazy revs and a piston to match (air cooled suitable).

[Roflhat]

Will have to extend the hole quite a bit for it to be open at TDC, is the stock piston strong enough?

download own photos from instagram

Yeh running the standard exhaust with a cone welded inside it then closed up again

[TZ350]

Will have to extend the hole quite a bit for it to be open at TDC, is the stock piston strong enough?

I made a mistake. I should have said "piston hole fully exposed in the slot from TPO to BDC", transfer port opening to bottom dead center, not TDC to BDC. Sorry.

Is the stock piston strong enough, I don't know. I never used them. I favored aftermarket pistons with a single thin ring.

[F5 Dave]

Std Suzuki pistons are fine for road type revs, but grim thereafter. The heavy rings will flap, lose contact with the bore and promote overheating which on aircooled is not pretty.

Std rods are pedestrian as well. Decide what revs you need and engineer to suit.

[speedpro]

I agree with what the 2 above said. If you do end up having to use the standard piston remove the 2nd ring. If everything else is good it will be fine. Also polish all the sharp edges on the piston particularly the bit below the pin. I did that and the pistons still had to be replaced every 2 meetings due to cracks.

[Roflhat]

Cheers, will check the rules but I think I can change rod and piston. Original parts have to be engine cases, barrel, exhaust, Venturi size

[F5 Dave]

Ok so you need to see if you gut the chamber, if you build something inside it that, - will it be of any worth? May be worth choosing a bike with the biggest pipe.

Std crank and piston with peak set for 10,500 would be quite reliable, but you can push that for your purpose.

But with some decent spinning parts, the gain in revs will surpass clever porting. Obviously you want to employ every trick.

Engineer first. Tune 2nd.

Um. . . Read rules first. Engineer 2nd, etc.

. . . so, barrel must be std. . . looking.

Head? Watercool that puppy if rules allow (or dont disallow).

[TZ350]

.
The KT100 GoKart engines rod assembly with 14mm L/E pin (The same rod as an RD125 I think) may be an easy suitable conversion for the GP. We used bigger 22mm BE pins and rods from RGV's and Yamaha RD's because of the superior flat cage silver plated big end bearings that are available for them. And their 15 or 16 mm little end pin option allowed us a better choice of piston for the GP125 and to spin reliably to 14,000 RPM on occasions.



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).

[ken seeber]

I agree with what the 2 above said. If you do end up having to use the standard piston remove the 2nd ring. If everything else is good it will be fine. Also polish all the sharp edges on the piston particularly the bit below the pin. I did that and the pistons still had to be replaced every 2 meetings due to cracks.

Over here in the land of Oz, there was a kart engine called the Comer S80/SW80, which had a 2 ring piston and chrome bore. The rules stated that both rings must be in place. So, to reduce friction, some guys removed the 2nd ring and squeezed it down to a helical shape such that the ends overlapped a bit. Then hit it with some heat (oven, torch ?) such that it took on a set to the new shape. Then it was refitted, where it sat tight in the groove and not contacting the bore. I think that these were CI as the bore surface being chrome, the normal chrome plated rings could not be used.

[Roflhat]

Looking at other sub 100cc bikes available in 1980 doesn't seem many had big pipes. RM100 probably the best, 19.5hp standard

These are the rules stated for production class engines

"Use the same engines (gasoline only) originally
installed in the specific motorcycle frame at the time
of production and ensure it meets the definition set in
the ‘P’ frame class (See 3.11D). Original equipment
(OEM) shall include cylinders, cases (crankcases),
heads, and carburation or throttle body (stock venturi
size), kick-starter or electric starter. Displacement
determines the class. OEM displacement specifications
must remain stock. "

[F5 Dave]

So you need to see what P frame class means, and what gearing is ultimately useable. YZ100 used some reasonable internal bits if you can find one.

Pipe would dictate revs if it has to look the same, but not be untouched. Otherwise it might have a shorter and internal baffle cone.

[wobbly]

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

[husaberg]

http://bonnevillespeedtrials.com/wp-...leSR-FINAL.pdf

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. They shall also contain the enginethat they were originally produced with. Driveline method/typemust remain stock (i.e. belt drive must remain belt drive)


12. A. PRODUCTION (P)Use the same engines (gasoline only) originally installed in thespecific motorcycle frame at the time of production and ensure itmeets the definition set in the ‘P’ frame class (See Chapter 4).Original equipment (OEM) shall include cylinders, cases(crankcases), heads, and carburation or throttle body (stock venturisize), kick-starter or electric starter. Displacement determines theclass. OEM displacement specifications must remain stock.GASOLINE ONLY. Fuel not permitted in this class. See Chapter2, paragraph 2.F.P engine class shall not run in M, MPS, A, APS or S frame classes

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