I Don't think the fuel with 15% oil is the problem, I have used this fuel on all my engines (both 2 and 4 strokes) for several years without any problem at all.
This weekend I tried to run the engine at several different fuels with more oil but the problem is the same, when I run the engine at full speed it leans, and when taking it back to idle it gets to much fuel and stops. It looks like the pump doesn't work at full speed and pumps to much fuel at idle.

I have been running the engine almost 2 gallons of fuel this weekend and tried almost every needle settings possible. I'm not new to 4 stroke engines and several other "experts" has tried to get this engine running properly this weekend with no success.

Any advice?

Sondre