2 stroke power valve comparison (cycle world 1986)

Aceofspades
Edited Date/Time 11/11/2015 9:49pm

















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Aceofspades 11/3/2015 7:44pm
11/3/2015 7:44pm
I firmly believe that the resonance chamber - type power valves were pure snake oil. I'd love to see a dyno chart proving they ever worked.
Cancerman
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Cancerman 11/4/2015 9:39pm
11/4/2015 9:39pm
I had an 85 CR125 that I raced until 1988. I started with the stock pipe and chamber, since I bought it new, and bought an PC pipe. After a while, since the pipe eliminated the chamber, I cut the pipe, and fabbed the end to use the chamber again. I noticed no gain in low or mid. The PC pipe started at mid and added to the top. The chamber killed the gains in mid to top. I chopped up the pipe again, rolled a new end piece, re added the flange and restored the pc pipe. I regained what I had lost. I just learned to ride it harder. I agree, I think the chamber was a marketing idea to compete with Yamaha and Kawasaki.
Aceofspades 11/4/2015 10:03pm
11/4/2015 10:03pm
I always wondered why the manufacturers didn't just use a variable port style. The we're already going to make new cases and cylinders, so why add a stupid resonator lol? I think the problem with most of them was that they were much to far away from the piston to be effective.
RyanLester761
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RyanLester761 11/11/2015 6:26am
11/11/2015 6:26am
Related story: I have an exhaust chamber eliminator piece off of my (sold) 1985 CR250. I assume this was a piece to run an after market pipe as stated above? Is it worth selling?

I bought a stock pipe when I was working on the project and it wouldn't fit until I found the chamber to re-attach and take up the gape. Thanks for shedding more light on that Jeff. Very interesting!

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Aceofspades 11/11/2015 9:49pm
11/11/2015 9:49pm
Those old power valves were true engineering trickery. I miss that kind of stuff

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