Polaris 2001 High-Performance Snowmobile Service Manual (PN 9916690), Page 113Get this manual
ENGINE Piston InspectionMeasurement
1Check piston for scoring or cracks in piston crown or pin areaExcessive carbon buildup below the ring lands is an indication of piston, ring or cylinder wear2Measure piston outside diameter at point 10 mm (38) up from the bottom of the skirt at 90 angle to the direction of the piston pin (domestic engines)For Fuji engines, measure 12 (12.7mm) up from the bottom of the piston skirtRecord the measurement for each pistonNOTE: The piston must be measured at this point to provide accurate piston-to-cylinder clearance measurement3Subtract this measurement from the minimum cylinder measurement recorded previouslyIf clearance exceeds the service limit, the cylinder should be re-bored and new pistons and rings installed
90 to pin