I had to chew on that carb issue for 7 years before the solution came floating up...

But before that, there were several issues that needed to be solved (that happened 7 years ago btw), such as that a tiny throttle orifice and a wide intake port (about 5 mm diameter) will lead to a near zero mixture velocity leading to oil pooling in the intake port. I solved that with an insert in the port, up to as close as possible to the valve area, reducing the inner diameter as far as I dared to go. Made that insert out out of POM, same stuff I made the carb header from.

Valve timing was another issue that I fixed last week. Strong reversal in the exhaust at the beginning of the intake stroke caused enormous amount of fouling of the combustion chamber.
Ground away the cam profile until there was virtually no more valve overlap, now the combustion chamber stays clean.

The governor is a Futaba GV1, intended for IC helicopters, a very weird controller, acually...
It wants to see the engine RPM as input signal, but its set value is the rotor RPM, and to make that work, you have to tell it the reduction ratio.

It has a working range of 1000 to 2000 RPM (rotor RPM...)

So I had to put 10 triggers on the flywheel and tell it there is a reduction ratio of 10:1 in order to trick it into thinking it sees 15K rpm, in order to achieve the desired 1500.

But hey, as long as it works...