Sym Jet 100 - Page 51

5. CYLINDER HEAD/CYLINDER/PISTON
5-2
Maintenance Information
Precautions In Operation
z The inspection and maintenance of the cylinder head, cylinder and piston can be carried as
engine mounted on the body.
z It should clean the engine to prevent dirt from entering into cylinder and crankcase before
removal.
z Remove all washes from the interfaces of cylinder head, cylinder and crankcase.
z Be careful do not damage cylinder head, cylinder and piston when removing.
z Inspect the removed & cleaned parts thoroughly, and apply with oil onto the rotation surfaces
before installation.
Specification
JET 50 series JET 100 series
Item
Standard value
(mm)
Limit (mm)
Standard value
(mm)
Limit (mm)
Cylinder
head
Deformation - 0.100 - 0.100
Piston OD 39.030~39.045 38.935 51.030~39.045 50.935
Clearance between
cylinder and piston
0.040~0.050 0.100 0.040~0.050 0.100
Piston pin hole 12.002~12.008 12.030 14.002~14.008 14.030
Piston pin OD 11.994~12.000 11.970 13.994~14.000 13.970
Clearance between
piston and piston pin
0.002~0.014 0.030 0.002~0.014 0.030
Piston ring end gap 0.100~0.250 0.400 0.100~0.250 0.400
Piston
ID of connecting rod
small end
17.05~17.015 17.025 17.05~17.015 17.025
ID 39.000~39.015 39.050 51.000~51.015 51.050
Cylinder
Deformation - 0.100 - 0.100
ID: inner diameter
OD: outer diameter
Tighten torque value
Cylinder head
1.0 kgf-m
Exhaust pipe connection nut
1.2 kgf-m
Spark plug
1.4 kgf-m
Exhaust muffler mounting bolt
3.3 kgf-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
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