My favorite aerobatic giant is (was) a 33% Extra-330 ARF from Modellmotoren powered by a 3W85 twin, JR 8103 radio with two 8411's on all the surfaces except rudder (pull-pull, 3 ganged 8411's).

I've got about 50 flights, no crashes on it. I went from perfect performance one day, to terror the next, getting multiple "hits" on rudder, elevator and aileron and even thottle on my last flight. By some freaky mix of skill and luck, I was able to land in one piece, partially because the "hits" seem less frequent and less intense at low throttle.

To make a long story short, I've gone over this plane and engine with a fine-toothed cob looking for a noise source. I STARTED with 24" of Nyrod throttle linkage, way-aft receivers, no metal clevises. I've taken apart every bolt and linkage, tried switching out my receivers, even the crystal module on the 8103. But I'm still getting hits on my ground checks, some even with the engine off, but more as engine is running and even more with increased rpm.

Should I change plugs? The whole ignition? HELP!!

mt