7. CYLINDER HEAD (2-STROKE)/ CYLINDER/PISTON VITALITY 50 A Mark The cylinder has a "A" mark or no mark on it. When replacing the cylinder with a new one, use a cylinder having the same mark as the old one. Measure the piston O.D. at a point 5mm from the bottom of the piston skirt. Service Limit: 38.90mm replace if below Measure the piston-to-cylinder clearance. Service Limit: 0.10mm replace if over Measure the piston pin hole I.D. Service Limit: 12.03mm replace if over Measure the piston pin O.D. Service Limit: 11.98mm replace if below Measure the piston-to-piston pin clearance. Service Limit: 0.03mm replace if over 7-10