I bought 1 of these engines a while back, and tried breaking it in. I could only get 8000 rpm out of an apc 15x8 and 8500 with an apc 14x8; this was after running 1/2 gallon through it. I called hobby services and they said to send it in. I decided to run it on a test stand and try 3 different props. On the teststand it would not draw fuel unless the throttle was at least 3/4 open. I figured the lsn needed richen, but how to get to the lsn? you have to remove the throttle arm screw to make an adjustment! I removed the carb and only could blow air through with the barrel 3/4 open. I drilled a hole through the arm screw so I could make adjustments without removing the arm. While reattaching the carb I looked in the intake tube and noticed 2 balls stuck in the bend. I knocked them loose, they were balls out of a bearing, how they got there I dont know. The engine went from box to plane back to box to test stand it has not been left out. The balls did not come out of the engine, I removed the back plate and looked. I reassembled the engine and started it on the test stand with an apc 15/8 andit was running at 9300 rpm hsn 2 turns out. I still need to adjust lsn because it was smoking.