Two stroke exhaust question.

[Suntan Sid]

Ok I know there’s a helluva lot of science goes into tuning two stroke exhausts, however I have a question for anyone versed in the dark arts of tuning two stroke pipes.

What are the end cans on a two stroke exhaust for?

Are they merely there for silencing purposes or does this part of the exhaust help with the tuning of the exhaust?

The reason I ask is if there is no requirement for silencing, if I replaced the baffle, within the can, with a tube would this improve the exhausts performance?

From what I’ve read I have a, sneaking, suspicion that it’s not that simple and the end can agitates the exhaust gasses which help the exhaust perform.

However on my, project, bike, (an RZ250R), I have read that repacking the end can, will help keep the bike running in top order, presumably because the exhaust gasses are exiting quickly, rather than swirling around the end can before being ejected.

Are there any websites, out there, that deal with this particular issue?

[MarJay]

Don't touch.

You can really mess up the performance of a two stroke by hacking away at the exhaust. RZ/RD exhausts are OK as they are. If you want more performance then you need to get a new set of expansion chambers built by someone who knows what they are doing. I've heard good things about Gibson, as they currently make 'AllSpeed' exhausts from original patterns.

Nikon, Jim Lomas, Jolly Moto and Arrow all make spannies for the RD IIRC, but I've heard that you need gearing changes to make the best from the Nikon and the Lomas, and the JM and the Arrow are both very very expensive. Stan Stephens reccomends them though.

With regard to your original question, the stinger doesn't make all that much difference to the performance of the exhaust, but it does make a difference. The real science is in the expansion chamber, but it does work in concert with the silencer.

I'd suggest either leaving it standard or going with a decent set of aftermarket 'spannies.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Kickstart]

Hi

Don't really think cans do anything special on 2 strokes (or 4 strokes). On a 2 stroke all the work is done by the expansion chamber.

All the best

Keith
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[Suntan Sid]

I’ve got no intentions of taking a hacksaw to the pipes; the cans are bolt on jobbies.
The standard pipes, that are on the bike, will do, (for now), however I was looking on the “TYGA” website, they only seem to do one, very skinny looking, can for all of their expansion chambers, which got me wondering.

If they do a one size fits all can across the whole range surely their effect on performance must be negligible.

While we’re on the subject, should I be able to remove the baffle completely (for cleaning and repacking purposes), from the cans I have?
At the moment when I remove the retaining screw, holding them in place, the baffle comes out about half way, then stops, is this correct?

[Kickstart]

Hi

I presume the baffles are a similar design to the ones in my TZR250. If so then they do come all the way out. However they can jam. Try rotating and wiggling the. Problem is that if they are slightly damaged the bits of the baffle catch on the baffle plates inside the cans.

On the TZR with a few spare sets of pipes some came out easily, while some took a fair amount of effort and abuse.

There is probably a foam seal between the baffle and the back of the cans. They are not that expensive (again assuming they are like the TZR) but new ones make getting the baffles back in far more difficult (I resorted to using a ratchet strap wrapped around the pipe front to back to push the baffle back in and hold it there while I bolted it in place).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing