hi i bought a non running yamaha sr 125.the guy told me it was stolen on him and got it back this way.the ignition barel smashed,fuse and wires pulled out,tank beat with hammer[or something like that] and a few other minor things.problem is when i got it home and wired it to turn over,there was no or little compression.[you dont get that because it was stolen].anyway i took the head off and the top of the piston is badly burnt and melted.the barel is ok.im going to put a new piston and rings on but before i do should i be looking for something else like what caused the piston to melt in the first place?and what else should i check before going ahead with the new piston

ragged to death I suppose, my daughter had a metro (car) stolen some years ago, it was recovered with a blown engine and the spark plugs had melted