I was down at the flying field today and the problem got worse. The engine started loosing high end power. If i left it around 1/4 throttle it couldnt hold stable rpm then suddenly die. So i packed it up came home, i checked the valves the 0.04mm feeler passes through easily but the 0.1 does not pass. Fresh bottle of YS 20/20 fuel.

I opened up the high end needle to 2 and 1/2 rounds then slowly closed it after changing to a 13x6 prop for a lighter load and noticed i could not take the engine to its optimal rpm range and at full throttle had much less power.

What way can i use to test regulator setting to know for sure if its rich / lean and what would make the engine loose power? I'm sure i didnt run it lean and the spark is shiny clean inside no black or anything.

Anyone please...