Just had out on new rear tire, chain and sprockets and chain guide/slider on my '11 kx250f, pulled it out into the yard to ride it around to make sure everything was in working order before loading up for the races. Bike started on the third kick as always. Idled for about 10 second and died. Started again in 3 kicks but was making an awful rattling sound. Pulled the head and found this sitting on top of the piston. Anybody have any idea what it is? Going to put a new piston in it now. Luckily the valves seem to be alright aside for a couple light "marks" on the left intake valve. I know it's hard to tell much in the picture, but would you run it like it is? Only have about 20 hours on the bike since new. The marks on the valves can't be felt, really more like it just kind of cleaned the carbon off. Thanks for any input.