ORIGINAL: Silversurfer
Bill,
Reading your post, that particular engine sounds more like a ring that hasn't seated for some reason, or even possibly stuck in the lands extremely early in the life cycle. That same condition could also be true for the engine that satrted this thread, but unfortunately I don't think so.
This is an excellent point for RCIGN, D. Hanson, and Preivers to shed some additional thoughts.
Pat,
The engine in question is on it's 5th gallon on 32:1 ashless. The pilot is a pretty decent, but fairly new gas pilot. He asked me to look into it and help him tune it better. The numbers I quote were after I leaned it. It was 4-stroking allo the way through the transition when I first started. It may have been run a bit lean at first but according the this person it was at the factory settings the whole time which would cause an oil buildup on the ring
I did mention the ring being stuck and we did pull the exhaust off and on that side it looked good. The plug was very close to being fouled due to how rich it was running previously but after 6 pretty hard flights the plug was coming around and the engine was running like one would expect a DA to run. It just felt weird flipping the prop to start it