7. CYLINDER HEAD (2-STROKE)/ CYLINDER/PISTON VITALITY 50 SERVICE INFORMATION (2-STROKE) GENERAL INSTRUCTIONS · The cylinder head, cylinder and piston can be serviced with the engine installed in the frame. · Before disassembly, clean the engine to prevent dust from entering the engine. · Remove all gasket material from the mating surfaces. · Do not use a driver to pry between the cylinder and cylinder head, cylinder and crankcase. · Do not damage the cylinder inside and the piston surface. · After disassembly, clean the removed parts before inspection. When assembling, apply the specified engine oil to movable parts. SPECIFICATIONS Standard (mm) Service Limit (mm) Item 2-Stroke Cylinder head warpage 0.10 Piston O.D.(5mm from bottom of piston 38.97038.955 38.90 Cylinder-to- piston clearance 0.10 Piston pin hole I.D. 12.00212.008 12.03 Piston pin O.D. 11.99412.0 11.98 Piston-to-piston pin clearance 0.03 Piston ring end gap (top/second) 0.100.25 0.40 Connecting rod small end I.D. 17.00517.017 17.03 Cylinder bore 39.039.025 39.05 TORQUE VALUES Cylinder head bolt 1.01.2kg-m Exhaust muffler joint lock nut 1.01.4kg-m Exhaust muffler lock bolt 3.03.6kg-m Spark plug 1.11.7kg-m TROUBLESHOOTING Compression too low, hard starting or poor performance at low speed Abnormal noisy piston · Leaking cylinder head gasket · Worn cylinder and piston · Loose spark plug · Worn piston pin or piston pin hole · Worn, stuck or broken piston and piston rings · Worn connecting rod small end bearing · Worn or damaged cylinder and piston Compression too high, overheating or knocking Abnormal noisy piston rings · Excessive carbon build-up in cylinder head · Worn, stuck or broken piston rings or on piston head · Worn or damaged cylinder 7-3