PGO ALLORO 125, Service Manual

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(4)Cylinder and piston:
A. Troubleshooting.
a. compression pressure is too low, difficult to start engine and running unsmoothly.
1. Cylinder head gasket cracked.
2. Spark plug is not well-locked.
3. Piston ring worn out or cracked.
4. Cylinder, piston worn out.
5. Reed valve is defective.
b. compression pressure is too high, engine overheating or abnormal noise.
1.piston tip has too much carbon piled up.
c. Abnormal piston noise
1. cylinder and piston worn out.
2. Piston pin hole or piston pin worn out.
3. Connecting rod small-end or bearing worn out.
d. Abnormal piston or cylinder noise
1.piston ring worn out or cracked.
2.Cylinder worn out or cracked.
B. The operation notice:
1.clean before operation to avoid particles dropping into engine.
2.The connect surface of gasket must be clean.
3.Dismantle the cylinder and the cylinder head by screw driver.
Do not scratch the contact surface.
4.Cylinder inner surface and piston outer surface can’t be scratched.
The contact surface should be lubricated by specified oil.
C. PISTON & CYLINDER DATAS:
Part name/description
Standard Value
(mm)
Limit of use
(mm)
Cylinder head Flatness 0.100
cylinder Bore 39.995~40.015 40.050
Piston/
Piston ring Lst ring
0.05~0.06 0.10
Clearance b/w Piston
ring piston and
2
nd
ring 0.05~0.06 0.10
Piston outer diameter 39.950~39.970 39.895
Measuring location of piston outer dia.
(12mm from the lower end of skirt)
Clearance b/w piston and cylinder 0.045~0.065 0.10
Piston pin hole inner dia 13.022~13.013 13.045
Piston pin hole inner diameter 10.002~10.008 10.025
Piston pin outer diamerer 9.994~10.000 9.970
Clearance between piston and piston pin 0.004~0.018 0.030
Connecting rod small end inner dia 13.996~14.007 14.025