I had a couple of L's do this: "The problem is, when engine warms, it loses power. Then, it's hard to start up. When it starts, it surges, then clears but only achieves partial power at full throttle, ... Does it also smoke a lot? Mine did. This happened when the engine was getting worn in both cases. One case required a new piston as well as some parts up there -- the piston was badly scored on the skirts from rocking. In both cases the engines were sent in for service so I don't have a good handle on exactly what to do. I have heard from reliable places that as the parts heat up "stuff" starts blowing by the ring/piston and causing the symptoms you describe and what I saw. I finished a contest with an engine like that by continuing to use Wildcat YS 20/20 fuel and switch from the 16X10 to a 15X12W. It took some of the load off the engine and I was able to fly it. I flew the rebuilt engine part of the next season with that 15X12W and it seemed quite happy -- granted I had to relearn the throttle positions but I think it was a better combination.

In the 2 or 3 weeks leading up to the contest problems, I think it was telling me it was in trouble but I didn't pay attention. At initial run up I go up slowly on the throttle until it is wide open -- stay there for maybe 5 seconds. I started noticing a slight drop in RPM after 4 sec. or so -- then it started happening a little sooner and with a slightly bigger drop. I'm thinking maybe it's a litle rich so I leave it -- rich is good, safe, etc... I think it was the fit loosening as it warms up (gets hot).

You might also post this question in the engines/manufacturers thread. Dave Shadel is pretty good at answering.

I just got another L back from Gardenerville but will probably have to wait til next spring to try it out (Minnesota...). Same symptoms, long in the tooth...the engine, not me.

Good Luck, Tom