Well, i've got 5 flights on my Evolution 26GT and on my 5th flight it quit 3 mins into the flight. I'm running the stock evolution pipe and header on premium fuel and lawnboy ashless oil for break in and a Top Flite 18x6 prop. My DA50 and DA100 both run great and my Evolution did run great up until this point. It quit 3 mins into the flight so it didn't run out of fuel. The battery pack is brand new with 5.6V and the ignition seems to be working properly as I just pulled the plug and turned the motor over with lots of spark. I noticed that the top of the piston is coated in a black like tar substance which, as far as i know, shouldn't be there. I haven't taken the head off yet becuase i'm thinking of sending it back to evolution. The plug appears to be fine. I haven't looked at the carb yet though. Anybody have any ideas of where to look?