Compression Too Low Or Uneven Compression; Excessive Smoke From Exhaust Muffler; Abnormal Noisy Piston - KYMCO Super 8 50 Service Manual

8
. CYLINDER/PISTON
SERVICE INFORMATION ....................... 8-1
TROUBLESHOOTING .............................. 8-1
CYLINDER REMOVAL ............................ 8-2
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
I.D.
Warpage
Cylinder
Cylindricity
True roundness
Ring-to-groove Top
clearance
Ring end gap
Piston,
piston ring
Piston O.D.
Piston O.D. measuring position 8mm from bottom of skirt
. 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
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, stuck or broken piston rings
 Worn or damaged cylinder and piston
Compression too high
 Excessive carbon build-up in combustion
chamber or on piston head
8-1
Item
Second
Top
Second
Oil side rail
PISTON REMOVAL ................................. 8-2
PISTON INSTALLATION ........................ 8-6
CYLINDER INSTALLATION .................. 8-6
Standard (mm)
39.00-39.01



0.015-0.050
0.015-0.050
0.06-0.16
0.13-0.28
0.20-0.70
38.855-38.875
0.010-0.040
13.002-13.008
12.994-13.000
0.002-0.014
13.016-13.034

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
Super 8 50
Service Limit (mm)
39.1
0.05
0.05
0.05
0.09
0.09
0.45
0.45

38.8

0.1
13.04
12.96

13.06