Using the Evo (aka Jett) tuned muffler is very tricky on a gas engine. I tested one out on the 9cc gas engine, and I had to run the engine quite a bit on the rich side too much. otherwise it would lean out when it came up on the pipe, so to speak. At the time, I needed to momentarily pinch the fuel line to get it to come up on the pipe, and even then it felt like it was still a little on the lean side. So I think one would need a in flight mixture control setup on the main needle to tweak it a little in the air to get it set just right. But the performance was pretty spectacular though, as the 9cc engine's port timing is more suited to a tuned pipe, so the performance boost was something spectacular. it really started howling like it was on a tuned pipe, up in the 15,000 RPM range.

but then the Evo 10cc has a needle bearing rod and will be less sensitive to running a little bit lean, so it might just work out Ok with it. I do have the muffler, so I'll defintely have a go at it later.


Here it is from my earlier experiments on the 9cc gas engine. So yeah it ought to be interesting on the Evo 10cc engine.