Shibaura ST330, Workshop Manual

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2) Cylinder head ass’y
Disassembly
(1) Using a valve spring replacer, compress the valve spring
to remove the valve cotter, retainer, spring and valve.
(2) Remove the valve guide seal.
109Y
Inspection and service
(1) Distortion of cylinder head bottom surface Apply a straight
edge to the bottom surface of the cylinder head, and insert a
thickness gauge at 6 points from A to F in the right figure
and measure distortion. If the distortion exceeds the repair
value
, replace with new one.
Distortion at cylinder head bottom surface (mm)
Standard assembling value Repair value
Less than 0.05 More than 0.12
(2) Valve guide and valve stem
➀ Check the head and stem of each valve and replace if
burnout, wear or deformation is remarkable.
➁ Measure the outside diameter at the position I, II, and
III on the valve stem with a micrometer and replace if
the result is less than the service limit.
➂
Replace a valve if its head thickness is less than service
limit.
110Y
Wear of valve stem (mm)
Intake valve Exhaust valve
Standard
assembling
value
Service
limit
Standard
assembling
value
Service
limit
6.955 – 6.97 6.89 6.94 – 6.95 6.84
111Y
112Y
Valve head thickness (mm)
Standard assembling value Service limit
0.775 – 1.075 Less than 0.5
1. Valve guide seal
2. Spring
3. Retainer
4. Valve
5. Valve cotter