I have one of these engines. I had to adjust the valves once as well. Sine then it has always run well. It sounds like you are on the right track. Keep using your tack and /or a temp gun as you adjust it. You really don't want to run it too lean, although it doesn't sound like that is your problem at this time. Is the crankcase vent line open and clear? Let us know how it goes after you adjust the valve and make sure the crankcase nipple and line are clear. FWIW, I run 15% heli fuel in all my 4 strokes for the higher oil content. Andy