score marks on piston

[91RM250]

hi guys got a little problem i recently replaced my piston and have only had it running for about 2 hours and have noticed that there are some significant scratches/score marks on the piston there only on one side that faces towards the back of engine not the power valve exhaust side, my crank is currently in to have bearings replaced and a new con rod kit as the old one was pretty poor state, could that have been the problem or could it be something else, like the cylinder may need replate. any help or suggestions would be great thanks guys.

[rmzracer289]

If you run your finger nail across the score marks and it doesnt catch it should be ok. I rebuilt an RM motor top to bottom, and replated the cylinder. I ran it for a couple hours and pulled the pipe off and saw score marks, I ran the bike the rest of the year and never had a problem.

[91RM250]

it runs fine, the sratches are quite bad and deep but not as bad as they could be just hope my new con rod and big end bearings should stop it going further but if it does pistons are easy to change anyway wont even need to take the engine out, but i will keep my eye on it, thanks for the advice.