Back in 1990 my local club (RC Country) put on pylon races with everyone flying a Bridi Aircruiser and a KB20 sportster. I finished the plane on Thursday and went to test fly it on Friday, the day before the race. I tried for 2 hours to get the engine to run; the only way it would run was with the pressure line disconnected. Finally I decided to take the engine apart, I found the piston and cylinder scored and the biggie....... The end of the muffler was completely sealed with flashing. The following week I took the engine down to K&B (it was about 5 miles from where I worked.) and the guy there took 45 minutes to replace the piston, muffler, and case. Considering I only spent $30 buying the engine they really lost on this one. Never won any of the races with the engine, best were a couple of 3rds and 4ths. I still have the engine in a 15 size ME109 and it runs better than when it was new.