Sym GTS 250, Service Manual

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6. Cylinder Head / Valve
6-2
Precautions in Operation
General Information
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This chapter is contained maintenance and service for cylinder head, valve, and camshaft as well as
rocker arm.
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Cylinder head service can be carried out when engine is in frame.
Specification
Item Standard Limit
Compression pressure 12±2 kg/cm2 ---
Intake 34.880 34.860
Camshaft Height of cam lobe
Exhaust 34.740 34.725
ID of valve rocker arm 11.982~12.000 12.080
Rocker arm
OD of valve rocker arm shaft 11.966~11.984 11.936
Intake 4.975~4.990 4.900
OD of valve stem
Exhaust 4.950~4.975 4.900
ID of valve guide 5.000~5.012 5.030
Intake 0.010~0.037 0.080
Clearance between
valve stem and guide
Exhaust 0.025~0.062 0.100
Inner 38.700 35.200
Free length of valve
spring
outer 40.400 36.900
Valve seat width 1.600 ---
Intake 0.10±0.02mm ---
Valve
Valve clearance
Exhaust 0.15±0.02mm ---
Tilt angle of cylinder head --- 0.050
Torque Value
Cylinder head cover bolt 1.0~1.4kgf-m
Exhaust pipe stud bolt 2.4~3.0kgf-m
Cylinder head bolt 1.0~1.4kgf-m
Cylinder head Nut 3.6~4.0kgf-m
Sealing bolt of cam chain auto-tensioner 0.8~1.2kgf-m
Bolt of cam chain auto-tensioner 1.2~1.6kgf-m
Cylinder side cover bolt 1.0~1.4kgf-m
Cam sprocket bolt 1.0~1.4kgf-m
Tappet adjustment screw nut 0.7~1.1kgf-m
Spark plug 1.0~1.2kgf-m
Tools
Special service tools
Valve reamer: 5.0mm
Valve guide driver: 5.0mm
Valve spring compressor
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