What would have caused this

[Mitymouse]

This is the piston from my Dolmar 120 which i just got off of craigslist last week. The amazing part is that it started and ran very well and didn't make any weird noises. I noticed some aluminum transfer onto the cylinder and some scouring on the exhaust side of the piston. So I took it apart to clean up and this is what I found. The pictures are on the intake side of the piston. While inspecting I noticed a few gouges in the exhaust port, so the pieces must have made there way through the engine. I was able to clean up the cylinder and while I was at it I midly ported and polished the exhaust port. Would it be possible to continue to use this piston or is this like playing russian roulette?

 

[Jacob J.]

Looks like it was over-speeding or the piston was worn and rocked back and forth in the bore. I'd get a new piston, they're a dime a dozen for the 120. In fact, I think Meteor sells an aftermarket replacement that's gotten good reviews.

 

[Mitymouse]

I have seen many pistons for 120si but not for the standard 120.

 

[Jacob J.]

Have you called Amick's?

 

[Tree Sling'r]

Piston slop would be my guess.