Well as usual...two steps forward and one step back. I bypassed the cutoff and I still had the problem. BUT...I noticed that the throttle servo was jumping as well. So I thought I figured out my RF noise source. I changed out with a way overkill MKS servo but I STILL have the problem.

Then the truly bizarre started to happen. The engine started to run really rough and seem unresponsive to throttle inputs. (in spite of the mechanical throttle assembly moving) Also, I switched on and off my cutoff and for the first time, I got jitters with just the throttle enabled but not running. The only thing I can figure is that this leads me to believe that it is my ignition. I double checked the plug connections and they were rock solid. Does the ignition seem like the most likely cause here. I double checked the voltage on the battery and it was 6.1Volts going into the ignition so a weak battery can be ruled out.

I guess I should call DA tomorrow.

First, define the cutoff you referred to above. If it's an electronic style be sure to leave it out for the test if not already. But it does sound like ignition module based in your post. If you can make it act up again when not running make sure to disconnect the module from sensor first, then module from battery and see which stage clears things up.

Victory! I got the call from Desert Aircraft today. There was an intermittent grounding error inside the ignition. Once the engine started, the vibration amplified it causing all sorts of problems. Even the though the engine was used, DA knew from the serial number that everything was still under warranty. New ignition and engine are on the way home to me. Great service from the team there.

Thanks to everyone in this thread for the ideas and especially to those that pointed me in the direction of the ignition.

Maybe change the thread title now?
"Ignition caused interference" maybe?

Done! Thanks again.

Remove Futaba from the title. This is an ignition issue that would effect all brands.

Close the thread.