Sym JD05W User Manual

6. Cylinder Head/Cylinder/Piston
6-2
Maintenance Information
Precautions in Operation
y The inspection and maintenance of the cylinder head, cylinder and piston can be carried as engine
mounted on the body.
y It should clean the engine to prevent dirt from entering into cylinder and crankcase before removal.
y Remove all washes from the interfaces of cylinder head, cylinder and crankcase.
y Be careful do not damage cylinder head, cylinder and piston when removing.
y Inspect the removed & cleaned parts thoroughly, and apply with oil onto the rotation surfaces before
installation.
Specification
Item Standard value (mm)
Cylinder head Deformation -
Piston OD 38.955~38.970
Clearance between cylinder and piston 0.030~0.050
Piston pin hole 12.002~12.008
Piston pin OD 11.994~12.000
Clearance between piston and piston
pin
0.002~0.014
Piston ring end gap 0.100~0.250
Piston
ID of connecting rod small end 17.005~17.017
ID 39.000~39.015 Cylinder
Deformation -
ID: inner diameter OD: outer diameter
Tighten torque value
Cylinder head 1.6~2.0kgf-m
Spark plug 1.1~1.7kgf-m
Exhaust pipe connection nut 0.8~1.2kgf-m
Exhaust muffler mounting bolt 2.4~3.0kgf-m
Troubleshooting
Compression Pressure Too Low/Difficult
To Start/Rough Idling
1. Cylinder head gasket leaking
2. Spark plug not tighten enough
3. Worn, seized or crack piston ring
4. Damaged, worn cylinder or piston
5. Poor reed
Compression Pressure Too
High/Overheat/Knock
1. Too much carbon deposit built up in
combustion chamber
Piston Noise
1. Cylinder and piston worn out
2. Piston pin or piston pin hole worn out
3. Connecting rod small end bearing worn out
Piston Ring Noise
1. Worn, seized or crack piston ring
2. Cylinder worn out or damaged

Sym JD05W Specifications

General

Brand	Sym
Model	JD05W
Category	Scooter
Language	English