Service Information; Troubleshooting - KYMCO MXU 500 Owner's Manual

9. CYLINDER/PISTON

SERVICE INFORMATION

GENERAL INSTRUCTIONS
The cylinder and piston can be serviced with the engine installed in the frame.
When installing the cylinder, use a new cylinder gasket and make sure that the dowel pins are
correctly installed.
After disassembly, clean the removed parts and dry them with compressed air before inspection.
SPECIFICATIONS
I.D.
Warpage
Cylinder
Cylindricity
True roundness
Ring-to-groove
clearance
Piston, Ring end gap
piston ring
Piston O.D.
Piston O.D. measuring position
. Piston-to-cylinder clearance
Piston pin hole I.D.
Piston pin O.D
Piston-to-piston pin clearance
Connecting rod small end I.D. bore
TORQUE VALUES
Cylinder bolt

TROUBLESHOOTING

When hard starting or poor performance at low speed occurs, check the crankcase breather for
white smoke. If white smoke is found, it means that the piston rings are worn, stuck or broken.
Compression too low or uneven
compression
Worn or damaged cylinder and piston rings
Worn, stuck or broken piston rings
Compression too high
Excessive carbon build-up in combustion
chamber or on piston head
Item
top
Second
top
Second
Oil side rail
1 kgf-m (10 N-m, 7.2 lbf-ft)
Standard
92.005 (3.6802)阡92.015 (3.6806)
0.01 (0.0004)
0.01 (0.0004)
0.01 (0.0004)
0.03 (0.0012)阡0.065 (0.0026)
0.015 (0.0006)阡0.05 (0.002)
0.15 (0.006)阡0.3 (0.012)
0.03 (0.012)阡0.45 (0.018)
0.2 (0.008)阡0.7 (0.028)
91.96 (3.6784)阡91.98 (3.6793)
10 mm from bottom of skirt
0.01 (0.0004)阡0.045 (0.0018)
22.002 (0.8801)阡22.008 (0.8803)
21.994 (0.8798)阡22 (0.88)
0.002 (0.0001)阡0.014 (0.0006)
22.016 (0.8806)阡22.034 (0.8814)
Excessive smoke from exhaust muffler
Worn or damaged piston rings
Worn or damaged cylinder and piston
Abnormal noisy piston
Worn cylinder, piston and piston rings
Worn piston pin hole and piston pin
Incorrectly installed piston
MXU 500
Unit: mm (in)
Service Limit
92.1 (3.684)
0.05 (0.002)
0.1 (0.004)
0.1 (0.004)
0.08 (0.003)
0.065 (0.0026)
0.5 (0.02)
0.65 (0.026)
1 (0.04)
91.9 (3.676)
－
0.1 (0.004)
22.04 (0.8816)
21.96 (0.8784)
0.02 (0.001)
22.06 (0.8824)
9-2