Sym Mio 50 User Manual

7. Cylinder / Piston
7-2
Operational Precautions
General Information
y Both cylinder and piston service cannot be carried out when engine mounted on frame.
Specification Unit: mm
Model HU10U/W HU05U
Item
Standard Limit Standard Limit
ID
49.995~50.015 50.500 37.015~36.995 37.500
Bend / wrap age
－
0.050
－
0.050
Cylindrical roundness
－
0.050
－
0.050
Cylinder
Cylindrical roundness
－
0.050
－
0.050
top ring 0.015~0.050 0.090 0.015~0.050 0.090
Clearance
between piston
rings
2
nd
ring 0.015~0.050 0.090 0.015~0.050 0.090
top ring 0.100~0.250 0.500 0.100~0.250 0.500
2
nd
ring 0.100~0.250 0.500 0.100~0.250 0.500
Ring-end gap
oil ring 0.300~0.900
－
0.2~0.7
－
OD of piston
49.970~49.990 49.900 36.985~37.005 36.900
Piston OD measurement
position
Lower-end up 9mm
of piston skirt
－
Lower-end up 9mm
of piston skirt
－
Clearance between piston
and cylinder
0.005~0.015 0.100 0.005~0.015 0.100
Piston/
Piston ring
ID of piston pin boss
13.002~13.008 13.040 10.002~10.008 10.040
OD of piston pin
12.994~13.000 12.960 10.000~10.006 9.966
Clearance between piston and piston pin
0.002~0.014 0.020 0.002~0.014 0.020
ID of connecting rod small-end
13.016~13.034 13.060 10.016~10.034 10.060
Trouble Diagnosis
Low or Unstable Compression Pressure
Cylinder or piston ring worn out
High compression Pressure
Carbon deposit onto piston and combustion
chamber
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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Sym Mio 50 Specifications

General

Brand	Sym
Model	Mio 50
Category	Scooter
Language	English