After further investigation, I found that the carburetor throttle plate has a small rounded notch in it just behind one of the fuel passages.

Even with the throttle plate fully closed, air and fuel will be introduced into the engine, allowing it to run at "closed throttle"

I doubt that the MVVS carb has such a notch.

This particular carb must have been designed to be used on a blower or chain saw that needs to idle, but must be turned off using ignition kill, unlike airplanes.

This is 100% different than airplane engines that must be able to be shut off using the transmitter. I use fully closed throttle.

The fix? I took the throttle plate out, soldered the notch closed and filed the plate so it fit the throttle bore again.

Results? It idles at 1400 RPM and will shut off at full throttle closed.

I'm using a Bisson side mounted muffler and APC 18-8 wide blade prop.

Top RPM is 7950, with only half an hour on the engine.

How does this compare to the mVVS 1.60?