Fred, I've got an O.S. 52 mounted with the head at 7:30. Not fully inverted, but almost. That enginge runs awful for the first two minutes or so from cold. It won't spool up right, sometimes quiting at more than 1/4 throttle. The strange thing is that once it is warmed up, it is solid as a rock. Once it cools of, it is back to it's bad habbits.

I pulled the rocker cover to check the gap a while back, and about a half teaspoon of oil poured out. My guess as to what is going on with it is that the rocker cover, and the piston are collecting a load of oil after running. The crank vent is now on top, so what ever collected around the cam, can only drain into the rocker cover. My theory is that this oil is screwing things up untill it gets heated up well and vaporizes again. If I don't wait to long between flights, or it is a hot day, the first start of the day is the only troublesome one. I've just come to accept this and I let the engine run for at least two minutes at over 1/2 throttle prior to the first flight. I'm wondering if you may have some of the same issues.

Don