KYMCO Venox 250, Service Manual

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7
. CRANKSHAFT/PISTON/CYLINDER
7-2
VENOX250/250i
SERVICE INFORMATION
GENERAL INSTRUCTIONS
x
Both of crankcase need to be replaced if anyone crankcase is damaged.
x
After disassembly, clean the removed parts and dry them with compressed air before inspection.
SPECIFICATIONS
Standard (mm) Service Limit (mm)
Item VENOX 250 VENOX 250
I.D. 58.0
阡
58.015 58.30
Warpage
 
Cylindricity 0.1 0.2
Cylinder
True roundness 0.005 0.01
Top 0.02
阡
0.06 0.09
Ring-to-groove
clearance
Second 0.02
阡
0.06 0.09
Top 0.1
阡
0.25 0.5
Second 0.2
阡
0.35 0.5
Ring end gap
Oil side rail 0.2
阡
0.7 0.9
Piston O.D. 57.975
阡
57.99 57.80
Piston O.D. measuring position 10mm from bottom of skirt
Piston-to-cylinder clearance 0.005
阡
0.065 0.125
Piston/
piston
ring
Piston pin hole I.D. 16.0
阡
16.006 16.012
Piston pin O.D 15.994
阡
15.997 15.90
Piston-to-piston pin clearance 0.001
阡
0.007 0.01
Connecting rod small end I.D. 16.013
阡
16.028 16.032
Connecting rod big end side clearance

0.40
Crankshaft runout

0.10
Crank-to-crankcase clearance 0.07
阡
0.27 0.3.
TROUBLESHOOTING
x
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 Excessive smoke from exhaust muffler
x
Worn, stuck or broken piston rings
x
Worn or damaged piston rings
x
Worn or damaged cylinder or piston
x
Worn or damaged cylinder or piston
Compression too high Abnormal noisy piston
x
Excessive carbon build-up in combustion
x
Worn cylinder, piston or piston rings
chamber or on piston head
x
Worn piston pin hole or piston pin