dents in my metrakit piston

A couple of weeks prior to the Cranks rally in Milwaukee, my newport started running poorly. It basically wouldn't do anything above half throttle. I figured it was jet related because that is usually where the main jet kicks in. However, that seemed odd because I've never changed the jetting on this bike before, regardless of the weather. So, during the weeks leading up to the rally, I worked on the bike quite a bit, but never solved the problem. I ended up taking it anyway, because it was the only bike I had and it would at least go 30.

Well, fast forward to the rally and the newport was just getting slower by the minute...until...I heard some loud, metal crunching noised and it died.

Last weekend I took the engine out and started to investigate. So far I have the head and the cylinder off and the only thing I found was some build up of carbon and possibly a little bit of metal in the dished area of the head. I also found these two dents in the top of my piston, in the same area where the build up was. Any thoughts? The cylinder and the piston both look good otherwise. There is no sign that they seized. The rings looks good, too.

My next step is to split the case halves and see if there are any problems in there. If not, I think I am going to clean up the top of the piston with dremel/file and put it all back together. Is the piston salvageable?