6. CYLINDER HEAD/CYLINDER/PISTON
6-2
SUPER8 50 2T
SERVICE INFORMATION
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
SUPER8 50 2T SUPER8 50 2T
Cylinder head warpage
⎯ 0.10
Piston O.D.(5mm from bottom of piston skirt)
38.970～38.955 38.90
Cylinder-to- piston clearance
0.10
Piston pin hole I.D.
12.002～12.008 12.03
Piston pin O.D.
11.994～12.0 11.98
Piston-to-piston pin clearance
←←
Piston ring end gap (top/second)
0.10～0.25 0.40
Connecting rod small end I.D.
17.005～17.017 17.03
Cylinder bore
39.0～39.025 39.05
TORQUE VALUES
Cylinder head bolt 1.5～1.7kg-m
Exhaust muffler joint lock nut 1.8～2.2kg-m
Exhaust muffler lock bolt 3.0～3.6kg-m
Spark plug 1.1～1.7kg-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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