Shibaura ST318, Workshop Manual

Page: 38 / 247

37
➃ Coat the valve seat surface with compound and lap
the contact surface turning the valve.
➄
Check that the valve contact surface is within the
standard value and the contact position is even.
➅ When the cylinder head is replaced with new one,
adjust the seat contact width and seat recess to the
specified values with a seat cutter before lapping.
(4) Valve spring
➀
Check the valve spring visually for damage.
➁ Measure the squareness of the spring using a square
on a surface plate and replace if the service limit is
exceeded.
➂ Check the free length and spring force with a spring
tester and replace if the service limit is exceeded.
(5) Inner face of combustion chamber
Pull out the cap and insert from the cylinder head.
Check and clean the combustion chamber.
NOTE:
1. Do not remove the insert.
T116
Standard
assembling value
Service limit
Squareness (mm) 1.2 More than 2
Free length (mm) 35 Less than 33.5
Spring force (when
compressed to 30.4
mm)
72.9 N
(8.1 kgf)
68.6 N
(Less than 7 kgf)
T117
T118
Reassembly
Reassemble components in the reverse order to disassembly taking care to the following point.
When assembling the valve spring, retainer and cotter, take deep care not to damage the valve guide seal.