Expansion chamber 50cc to 125cc?

[Reveeen]

My target size is 90cc, nothing available for my specific application (Honda Aero), so I'm going to have to cut and weld anyway. I have a NOS 50cc chamber here, but the RPM range is wrong (too high), probably better off with a 125cc chamber.

Anything out there?

[Weldangrind]

I have an exhaust that was originally installed on a CT Baja 50 four stroke (hear me out :) ). The Yamaha PW80 was so faithfully copied, that the manufacturer stuck an expansion pipe on the four stroke engine. You can imagine how long I left that on there.

The only other spare two-stroke pipe I have is from an old YB100, and it doesn't really have an expansion chamber.

The PW80 style chamber is yours if you want it.