I have a MS310 with a scored piston and cylinder. How do I determine what can be re-used and what needs replaced? Can the piston & cylinder be reused if buffed out and rings replaced? All the scoring is on the exhaust side. I didn't know about the trick of shoving rope in above the piston before breaking loose the clutch so I put a wrench in the exhaust port. This has created a small burr on the piston and top of exhaust port. (visible in photos) Advice appreciated!