RE: Black goo
OH, as if I didn't already post enough. The CRRC 40 engine has sort of a cup area near where the plug comes through. This catches this black goo. The symptoms will be an engine that starts, runs about 10 revolutions and quits. Just enough to keep you trying. Then, if you stay with it long enough, it might actually start and run. I have done this and had one of these cut off in flight under power. Until I cleaned it, this was a problem. Might start fine, then do this junk. The goo was forming a trace that was grounding out the spark. New plugs helped, but it got to the point of needing a new plug after every flight, even though the plug really didn't look bad. Maybe I was just disturbing the goo build up while changing the plug? We've had the same issues with Brillelli's, DAs, 3Ws and ZDZs. This pretty much ruined an entire year of flying my gassers for me.