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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
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