KYMCO Mongoose 50-2T, Service Manual

Page: 129 / 258

8
. CYLINDER/PISTON
8-5
SERVICE INFORMATION (50cc-2T)
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
mm (in)
Item
Standard Service Limit
Cylinder head warpage
⎯
0.1 (0.004)
Piston O.D.(3 mm, 0.12 in) from
bottom of piston skirt)
38.96
～
38.965 (15.584
～
15.586) 38.9 (1.556)
Cylinder-to- piston clearance 0.035
～
0.05 (0.0014
～
0.002) 0.1 (0.004)
Piston pin hole I.D.
12.002
～
12.008 (0.48008
～
0.48032) 12.03 (0.4812)
Piston pin O.D. 11.994
～
12 (0.47976
～
0.48) 11.98 (0.4792)
Piston-to-piston pin clearance
0.002
～
0.014 (0.00008
～
0.00056) 0.03 (0.0012)
Piston ring end gap (top/second) 0.1
～
0.25 (0.004
～
0.01) 0.4 (0.016)
Connecting rod small end I.D. 17.005
～
17.017 (0.6802
～
0.68068) 17.03 (0.6812)
Cylinder bore
39.005
～
39.01 (1.5602
～
1.5604) 39.05 (1.562)
TORQUE VALUES
Cylinder head bolt 10 N-m (1 kgf-m, 7 lbf-ft)
Spark plug 15 N-m (1.5 kgf-m, 11 lbf-ft)
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