Kymco MO Movie125, MO Movie 150 Service Manual - chap 08 (cil e pistone)
8. CYLINDER/PISTON
8-0
8
Do not bend
8. CYLINDER/PISTON
8-1
SERVICE INFORMATION
GENERAL INSTRUCTIONS
• The cylinder and piston can be serviced with the engine installed in the frame.
• After disassembly, clean the removed parts and dry them with compressed air before inspection.
SPECIFICATIONS
Item
Standard (mm)
Service Limit (mm)
I.D.
52.400_ 52.410
52.50
Warpageæ0.05
Cylindricity
æ
0.05
True roundness
æ
0.05
Ring-to-groove
Top
0.015_ 0.055
0.09
clearance
Second
0.015_ 0.055
0.09
Top
0.10_ 0.25
0.5
Piston,
Ring end gap
Second
0.10_ 0.25
0.5
piston ring
Oil side rail
0.2_ 0.7
æ
Piston O.D.
52.370_ 52.390
52.3
Piston O.D. measuring position
9mm from bottom of skirt
æ
.
Piston-to-cylinder clearance
0.010_ 0.040
0.1
Piston pin hole I.D.
15.002_ 15.008
15.04
Piston pin O.D
14.994_ 15.000
14.96
Piston-to-piston pin clearance
0.002_ 0.014
0.02
Connecting rod small end I.D. bore
15.016_ 15.034
15.06
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 Excessive smoke from exhaust muffler
• Worn, stuck or broken piston rings • Worn or damaged piston rings
• Worn or damaged cylinder and piston • Worn or damaged cylinder and piston
Compression too high Abnormal noisy piston
• Excessive carbon build-up in combustion • Worn cylinder, piston and piston rings
chamber or on piston head
• Worn piston pin hole and piston pin
Cylinder
SERVICE INFORMATION
......................
8-1 PISTON REMOVAL
.................................
8-3
TROUBLESHOOTING
.............................
8-1 PISTON INSTALLATION
.......................
8-6
CYLINDER REMOVAL
............................
8-2 CYLINDER INSTALLATION
.................
8-6
8. CYLINDER/PISTON
8-2
CYLINDER REMOVAL
Remove the cylinder head. (!7-6)
Remove the cam chain guide.
Remove the cylinder base bolts.
Remove the cylinder.
Remove the cylinder gasket and dowel pins.
Clean any gasket material from the cylinder
surface.
PISTON REMOVAL
Remove the piston pin clip.
Press the piston pin out of the piston and
remove the piston.
Dowel Pins
Gasket
Cylinder
Piston
Piston Rings
Place a clean shop towel in the crankcase
to keep the piston pin clip from falling
into the crankcase.
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