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Date: Tue, 12 Sep 2000 05:55:10
Subject: RE: performance exhaust
From: dwood
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There are lots of books on 2 stroke exhaust design. Building your own is
possible, if you can braze or weld ( or know someone who does). 2 stroke
and 4 stroke design are quite different so a 5 hp
B+S header isn't a great idea. 2 Stroke expansion chamber type exhausts use
pressure pulse timing and sonic wave action reflecting up and down the pipe
to influence the intake and exhaust events.
They can make large differences in power output. They also tend to work in
a narrow rpm range (shouldn't be a problem for mopeders - we all ride at
wide open throttle anyway ;).

Two books (among others) that have info are "The Two Stroke Tuners
Handbook" by Gordon Jennings
and "Motorcycle Tuning: Two Stroke" byJohn Robinson.

Expect to have to do some carburettor tuning to make it work right - as
wtih any modification that
changes the airflow in the engine.

If you can get access to an existing pipe, a copy might be a quick way to
go.

If you want to discuss it in more detail, drop me an e-mail -
dwood@hpi.net

-Dave

On Monday, September 11, 2000 9:51 PM, Gee0ff@aol.com [SMTP:Gee0ff@aol.com]
wrote:
> Im building a 79 Vespa Grande and would like to upgrade the exhaust. Does
> anyone have any ideas on buying or even building one? Any experience with
a
> straight pipe?
> What about tuned chambers? Cone sizes and length? Supertrapp style from a
5hp
> go-kart?! Are there and mopeds that came with a really good muffler that
> would be an improvement over stock?
> > Geoff
> list.

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