Have put about 8 litres through my 2105...it was a Yurugix prerun and I have taken it very easy on the engine and always been on the rich side of race tune. However, the piston still got a pickup where it passes the right hand edge of the exhaust port...similar to some of my 2104s.

Though it looks bad, i can bearly feel it with my nail and don't think it effects the performance much at all (engine is a monster)...just disappointing that OS released a new engine with old problems.