Motorcycle pistons are so highly stressed that there really is no substitute for a nice tight fit after a rebore. I've never even heard of knurling being used in a motorcycle engine and I'm pretty sure that Knurling hasn't been used in car engines for close to 40 years. They had some "cheepo" auto repair companies in Los Angeles many years ago that would actually advertise knurling your pistons and valve stems to do an "overhaul". An engine "rebuilt" like that would only be good enough to get you out the door. Oil burning was the rule of the day. All of those companies were put out of business after California set up the Bureau of Automotive Repair to cull them out.scarpatchy said:Thanks for the replies! I was afraid that knurling wasn't really in my son's best interest. He had a Buell conversion in his '94 883. It ran great except for what he thought was a "pinging" noise at certain times. He's had his bike back to the shop(Lancaster HD) so many times that I lost count. The tech finally admitted that pistons were on the upper limit for tolerances but that his boss(no longer working there) rushed the job and said that it would be alright. Well they planned on making it right for him at no cost to him. I guess some one that works there(the new boss?) and used to be in racing suggested knurling, probably to save the company money. Well it'll cost them more in the long run because he won't let them off the hook. Mabee I should e-mail the COMPANY and see how they feel about their shops doing this procedure. Thanks again for the help.