Johnson Evinrude Outboard Motors 1956-1970 1.5-40hp repair manual., Page 64Get this manual
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Check the piston ring grooves for wear, burns, distortion or loose locating pinsDuring an overhaul, the rings should be replaced to ensure lasting repair and proper engine performance after the work has been completedClean the piston dome, ring grooves and the piston skirtClean the piston skirt with crocus dothClean carbon deposits from the top of the piston using soft wire brush, carbon removal solution, or by sand blastingIf wire brush is used, TAKE CARE not to burr or round machined edgesWear pair of good gloves for protection against sharp edges, and dean the piston ring grooves using the recessed end of the proper broken ring as toolNEVER use rectangular ring to clean the groove for tapered ring, or use tapered ring to clean the groove for rectangular ringNEVER use an automotive-type ring groove cleaner to clean piston ring grooves, because this type of tool could loosen the piston ring locating pinsTAKE CARE not to burr or round the machined edgesInspect the piston ring locating pins to be sure they are tightThere is one locating pin in each ring grooveIf one locating pin is loose, the piston must be replacedNever attempt to replace the pin, it is NEVER successfulOversize Pistons and Rings Scored cylinder blocks can be saved for further service by reboring and installing