Compression Too Low, Hard Starting Or Poor Performance At Low Speed; Compression Too High, Overheating Or Knocking; Abnormal Noisy Piston; Abnormal Noisy Piston Rings - KYMCO SUPER8 50 2T Service Manual

6
. CYLINDER HEAD/CYLINDER/PISTON

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
Cylinder head warpage
Piston O.D.(5mm from bottom of piston skirt)
Cylinder-to- piston clearance
Piston pin hole I.D.
Piston pin O.D.
Piston-to-piston pin clearance
Piston ring end gap (top/second)
Connecting rod small end I.D.
Cylinder bore
TORQUE VALUES
Cylinder head bolt
Exhaust muffler joint lock nut
Exhaust muffler lock bolt
Spark plug
●TROUBLESHOOTING
Compression too low, hard starting
or poor performance at low speed
• Leaking cylinder head gasket
• Loose spark plug
• Worn, stuck or broken piston and piston rings
• Worn or damaged cylinder and piston
Compression too high, overheating
or knocking
• Excessive carbon build-up in cylinder head
or on piston head
Item
1.5～1.7kg-m
1.8～2.2kg-m
3.0～3.6kg-m
1.1～1.7kg-m
Standard (mm)
SUPER8 50 2T
⎯
38.970～38.955
12.002～12.008
11.994～12.0
←
0.10～0.25
17.005～17.017
39.0～39.025

Abnormal noisy piston

• Worn cylinder and piston
• Worn piston pin or piston pin hole
• Worn connecting rod small end bearing

Abnormal noisy piston rings

• Worn, stuck or broken piston rings
• Worn or damaged cylinder
SUPER8 50 2T
Service Limit (mm)
SUPER8 50 2T
0.10
38.90
0.10
12.03
11.98
←
0.40
17.03
39.05
6-2