DLE 20 drops rpm after 10 sec idle
My DLE 20 seems to be developing more and more of a problem. When I have the engine at idle for about 10 seconds the rpm will drop suddenly to about 60% of what it was. I've never put at tachometer on it but it is a significant drop. So much so that if I set up the throttle trim for an appropriate idle for a flight, it will drop so low during landing that the engine will quit.The engine is mounted in a 1/4 scale cub with a 17/6 prop. The engine is about 6 years old and has about 50 flights on it. Other than this problem it runs great. Could this be ignition, possibly something to do with timing changing?
Thanks in advance
Roy