Originally Posted by 22Racer

Sounds like you are very happy with the motor but the looks of the piston? High silicon content aluminum looks like that although yours does look a little different. They could have used a cheaper aluminum like Os does and you would need to have it pinched more often. ( I pinch motors) Just put it together and run it, if there was something wrong with the pston it would have lost pinch by now.
Or you could listen to Deadmancourt, can you tell he sells Go motors?

Rex