KYMCO Downtown 300i ABS, Service Manual

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7. CYLINDER/PISTON
7-2
Downtown 300i ABS
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
Item
Standard (mm) Service Limit (mm)
Cylinder
I.D. 72.705
～
72.715 72.80
Ring-to-groove top
0.015
～
0.055 0.09
clearance
Second
0.015
～
0.055 0.09
top
0.10
～
0.25 0.50
Piston, Ring end gap Second
0.10
～
0.25 0.50
piston ring Oil side rail
0.2
～
0.7
1.0
Piston O.D.
72.67
～
72.69 72.6
Piston O.D. measuring position
9mm from bottom of skirt
. 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 16.96
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 or damaged cylinder and piston rings
•
Worn or damaged piston rings
•
Worn, stuck or broken piston rings
•
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
•
Incorrectly installed piston