Hey mattnew, I tried a new spark plug today as you suggested and the engine ran great on the ground. I will give the engine and plane a good work out tomorrow. It looks as though you may have been correct about the old spark plug. It tested and looked OK but would not run. I guess it is easy for these small spark plugs to fool us. Thanks for your input.

Best wishes and good safe flying.

Heli-NuBee (AKA Roger the radial rabbit)