Got a free CS-510 saw today. Looked it over, has good spark and all but the the piston is shot. Not a tremendous amount of scoring but some present. the cylinder looks ok from what i can see. The biggest problem is it looks like the ring is ?melted? Anyway, want some opinions...should I a) fix it b)get rid of it or c) part it out. Basically Im asking is it worth rebuilding, the condition of the saw is what i would call good, doesnt look like it has seen a ton of use. Thanks