Precautions In Operation; Trouble Diagnosis - Sym Fiddle III 50 Service Manual

7. CYLINDER/PISTON

PRECAUTIONS IN OPERATION

General Information
Both cylinder and piston service cannot be carried out when engine mounted on frame.
Specification
ID
Bend/wrap age
Cylinder
Roundness
Cylindrical
Clearance between
piston and rings
Ring-end gap
Piston/
Piston ring
OD of piston
Clearance between piston and
cylinder
ID of piston pin hole
OD of piston pin
Clearance between piston and piston pin
ID of connecting rod small-end

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.
7-2
Item Standard
37.00
0.005
0.005
Top ring 0.025~0.060
nd
2 ring 0.015~0.050
Top ring 0.200~0.400
nd
2 ring 0.250~0.400
Oil ring
0.200~0.700
37.005~36.985
0.025~0.040
13.002~13.008
12.994~13.000
0.002~0.014
13.005~13.020
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.
unit: mm
Limit
－
0.050
0.050
0.050
0.090
0.090
0.500
0.650
0.100
13.040
12.980
0.018
13.040
SYM
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