I ran the engine a few times on the bench and everything was just fine. A few flips to bring the fuel up, turn the ignition and choke on, two flips til it pops, choke off, starts on the fourth flip every time. Idled great, instant transition, and ran up to full throttle just fine. Ran it a few minutes for each of 4 runs. No sign of the mysterious problem.

I guess I'll put it back in the plane and take her to the field and see what happens. If it gives me fits, maybe I'll try a different fuel. Thanks again for all the great advise!

BTW, I asked the guy at the lawn center if synthetic oil has been known to cause any problems for them and he never heard of probs. with it. But if something can cause problems, generally it will happen to me.

Ben