My bike has lost a little hp, a little harder to start and used a small amount of oil between changes. I decided it was time to freshen up the top end. I tore down my motor last night, and found the piston and cylinder to look a little on the rough side. The cylinder has ring grooves worn in at the top and bottom of the stroke (which honing will not remove) and has 2 scores on the intake side. Also matching scores on the piston below the rings. The scores are approximately .010 deep and maybe .030 wide and run from just below the ring to the bottom of the skirt. My question is, what caused that score? Crank and rod bearings seem to be ok, the bottom end was quiet before the tear down and everything worked good. Only issue I've had is sometimes 3rd gear can miss shift, but not all the time. I'm not sure if really there is any reason to tear the bottom end apart, but my engine guy is a little concerned about where the metal came from. I have not been getting any metal on my oil filter either. Any advise? Suggestions? Much appreciated!