I'm gonna jump off a limb here and say that the MVVS 1.6 gas engine looks suspiciously like the new Evolution 26 gas engine.

Right down to that heavy spring loaded choke lever and the adapter plate with crank pressure tube under the carb.

Maybe you can help.

I have had engines that would not keep running, but the EVO 26 won't stop! The throttle plate closes 100% and the carb is as tight as I dare tighten it.

It won't go below about 3500 RPM.

High speed is great. Maybe 7500 RPM with an 18-8, good transition, but it won't stop at idle

Looks to me like the adapter plate is leaking air.

One more thing. I am not running a muffler of any kind. None available here yet, but they promised one in a week.

Any Ideas? Has anyone else had this problem?

Maybe MVVS are indeed better engines?

Thanks