I turned the regulator screw in (clockwise) 1/2 turn. The main needle is at about 1 3/4 out. I don' t think prop size has anything to do with the problem.... By leaning the main needle a little more I can easily get it to 11000 with huge amounts of smoke still. It's really weird how it quits.... It runs fine and smooth, then just stops like if you snap the throttle closed. It's definitely not over heating either.....every time it happens the engine is pretty much average temperature, not on the hot side.