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If it was mine I would take the seal off the piston, and use a worn in or broken in flap wheel on a drill an 80 then a 120 grit, and run the wheel around the pistion like a tire rolling around the out side , the thought is to soften the edges of the scoring, I would not want a grove to be deeper then 1/16 inch maximum, then make sure the bore of the cylinder is free from burrs and run the flap wheel inside the ring retainer area and about 1 inch inside the cylinder, again make sure the flap wheel is broken in, you can do this by hitting the edge of a plate of steel.