CYLINDER HEAD, CYLINDER AND PISTON 6-17
• If the seat width
W
measured exceeds the standard value or
seat width is not uniform, refuse the seat using the seat cutter.
Valve seat width
W
:
Standard: 0.9 – 1.1 mm (0.035 – 0.043 in)
VALVE SEAT SERVICING
The valve seats
1
for both the intake and exhaust valves
2
are
machined to three different angles. The seat contact surface is
cut at 45°.
NOTE:
After servicing the valve seats, be sure to check the valve clear-
ance after the cylinder head has been reinstalled. (
2-25)
INTAKE
EXHAUST
Seat angle
15°, 45°, 60°
←
Seat width
0.9 – 1.1 mm
(0.035 – 0.043 in)
←
Valve diameter
31 mm (1.22 in)
25 mm (0.98 in)
Valve guide I.D.
4.500 – 4.512 mm
(0.1772 – 0.1776 in)
←
60
˚
45
˚
15
˚
* The valve seat contact area must be inspected after
each cut.
* Do not use lapping compound after the final cut is
made. The finished valve seat should have a velvety
smooth finish but not a highly polished or shiny fin-
ish. This will provide a soft surface for the final seat-
ing of the valve which will occur during the first few
seconds of engine operation.
The titanium valves are coated with an oxidized mem-
brane treatment to resist wear but the membrane tend
to be removed if lapped after valve seat servicing.
