Shibaura ST318, Workshop Manual

Page: 37 / 247

36
➃ Replace the valve if the clearance between the stem
and guide exceeds the service limit.
Clearance between valve stem and valve guide (mm)
Intake valve Exhaust valve
Standard
assembling
value
Service limit
Standard
assembling
value
Service
limit
0.03 – 0.06
More than
0.2
0.045 –
0.075
Mora than
0.25
T113
(3) Valve seat
➀
Since the valve seat is corrected according to the
valve guide, be sure to check the valve guide for
wear condition first before correcting the seat.
➁ Correct the seat to the standard assembling values
of the contact width and recess using seat cutters of
15°, 45° and 75°.
➂ When the seat recess exceeds the service limit,
replace the cylinder head.
Valve seat contact width (mm)
Standard assembling value Repair value
1.7 – 2.1 More than 2.5
T114
Valve seat recess (mm)
Standard assembling value Service limit
0.85 – 1.15 More than 1.8
T115