Sym Mio 50 - Operational Precautions

6. Cylinder Head / Valve
6-2
Operational Precautions
General Information
y This chapter is contained maintenance and service for cylinder head, valve, and camshaft as well as
rocker arm.
y Cylinder head service cannot be carried out when engine is in frame.
Specification Unit: mm
Model HU10U/W HU05U
Item Standard Limit Standard Limit
Valve clearance (intake/exhaust valve
as cold engine)
0.12 ± 0.02 ─ 0.05/ 0.10 ± 0.02 ─
Compression pressure
12 ± 2 kg/cm² ─ 9 ± 2 kg/cm² ─
Intake
25.969 25.570 24.100 23.761
Camshaft height of cam
lobe
Exhaust
25.891 25.410 23.850 23.369
ID of valve rocker arm
10.000~10.015 10.100 10.000~10.015 10.100
Rocker
arm
OD of valve rocker arm shaft
9.972~9.987 9.910 9.987~9.978 9.910
Intake
4.975~4.985 4.900 4.980~4.970 4.900
OD of valve stem
Exhaust
4.955~4.970 4.900 4.970~4.955 4.900
Guide seat
5.000~5.012 5.300 5.000~5.012 5.300
Intake
0.010~0.037 0.080 0.010~0.037 0.080
Clearance
between valve
stem and guide
Exhaust
0.030~0.057 0.100 0.030~0.057 0.100
Valve
Valve seat width
1.000 1.600 1.000 1.600
Connection Flatness of cylinder head
- 0.050 - 0.050
Torque Value
Cylinder head bolt (LH) 1.0~1.4kgf-m
Cylinder head left side bolt 1.0~1.4kgf-m
Cylinder head Nut 1.8~2.2kgf-m
Sealing bolt of timing chain auto-tensioner 0.8~1.2kgf-m
Bolt of timing chain auto-tensioner 1.0~1.4kgf-m
Valve adjustment nuts 0.7~1.1kgf-m (apply with oil on bolt thread & seat)
Spark plug 1.0~1.4kgf-m
Special service tools
Valve reamer: 5.0mm
Valve guide driver: 5.0mm
Valve cover wrench SYM-ALL12361
Valve spring compressor SYM-1471100 0r
Valve spring compressor/installer SYM-1471110/20
Valve clearance adjustment wrench SYM-9001200 or
Valve clearance adjuster SYM-9001210
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