Thanks for your info. I'll try a number 8 plug. One of the things I was wondering was if the outside temps were a factor. At full take off power, I could hold the cylinder head and it almost felt cold to the touch, the engine wasn't very hot after shutdown either.

I forgot to mention that the I had to replace the HotRod with a new one, it was a total loss. So the fuel set up on the new plane is good. (The clunk did go to the front of the tank on the crashed plane though!)

When I disassembled the engine, I checked very carefully for damage, especially in the carb. Everything seems to be in good order and the engine turns over well. I ran two tanks through it in the air on about half throttle, I didn't tempt taking it to full throttle in the air.

I'll try retuning the low end. The power is dropping off during the transition.

Thanks again.