7. CYLINDER/PISTON SYM
7-2
PRECAUTIONS IN OPERATION
General Information
Both cylinder and piston service cannot be carried out when engine mounted on frame.
Specification unit: mm
Item Standard Limit
ID 39.00 -
Bend/wrap age
－
0.050
Roundness 0.005 0.050
Cylinder
Cylindrical 0.005 0.050
Top ring 0.025~0.060 0.090
Clearance between
piston rings
2
nd
ring 0.015~0.050 0.090
Top ring 0.200~0.400 0.500
2
nd
ring 0.250~0.400 0.650
Ring-end gap
Oil ring
0.200~0.700 -
OD of piston 38.970~38.990 -
Clearance between piston and
cylinder
0.025~0.040 0.100
Piston/
Piston ring
ID of piston pin hole 13.002~13.008 13.040
OD of piston pin 12.994~13.000 12.980
Clearance between piston and piston pin 0.002~0.014 0.018
ID of connecting rod small-end 13.005~13.020 13.040
TROUBLE DIAGNOSIS
Low Or Unstable Compression Pressure
Cylinder or piston ring worn out.
Compress pressure to high.
Too much carbon deposited in combustion
chamber and piston.
Knock or Noise
Cylinder or piston ring worn out.
Carbon deposits on cylinder head top-side.
Piston pin hole and piston pin wear out.
Smoking in Exhaust Pipe
Piston or piston ring worn out.
Piston ring installation improperly.
Cylinder or piston damage.
Engine Overheat
Carbon deposits on cylinder head top side.
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