KYMCO MX'ER 50 - Cylinder Head;Cylinder;Piston; Service Information; Troubleshooting

7. CYLINDER HEAD/CYLINDER/PISTON
7-2
MX’er 50
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
MX’er 50
Item
Standard (mm)
Service Limit (mm)
Cylinder head warpage
æ
0.10
Piston O.D.(5mm from bottom of piston
skirt)
38.970_ 38.955
38.90
Cylinder-to- piston clearance
0.03_ 0.07
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
0.002_ 0.014
0.03
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 1.0_ 1.4kg-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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