Sym Orbit II 50 4T User Manual

7. CYLINDER/PISTON SYM
7-2
PRECAUTIONS IN OPERATION
General Information
Ÿ Both cylinder and piston service cannot be carried out when engine mounted on frame.
Specification unit: mm
Item Standard Limit
ID 52.395~52.415 52.50
Bend/wrap age Less than 0.05 0.050
Roundness Less than 0.01 0.050
Cylinder
Cylindrical Less than 0.05 0.050
Top ring 0.05~0.105 0.145
Clearance between
piston and rings
2
nd
ring 0.05~0.105 0.145
Top ring 0.100~0.2500 0.500
2
nd
ring 0.300~0.500 0.750
Ring-end gap
Oil ring
0.200~0.700
-
OD of piston 52.385~52.405 52.310
Piston OD measurement position
Lower-end up 7mm
of piston skirt
-
Clearance between piston and
cylinder
0.005~0.015 0.100
Piston/
Piston ring
ID of piston pin hole 15.002~15.008 15.040
OD of piston pin 14.994~15.00 14.96
Clearance between piston and piston pin 0.002~0.014 0.020
ID of connecting rod small-end 15 15.06
TROUBLE DIAGNOSIS
Low Or Unstable Compression Pressure
l Cylinder or piston ring worn out.
l Compress pressure to high.
l Too much carbon deposited in
combustion chamber and piston.
Knock or Noise
l Cylinder or piston ring worn out.
l Carbon deposits on cylinder head
top-side.
l Piston pin hole and piston pin wear out.
Smoking in Exhaust Pipe
l Piston or piston ring worn out.
l Piston ring installation improperly.
l Cylinder or piston damage.5
Engine Overheat
l Carbon deposits on cylinder head top
side.

Sym Orbit II 50 4T Specifications

General

Brand	Sym
Model	Orbit II 50 4T
Category	Scooter
Language	English