3-36 ENGINE
• If the seat width W measured exceeds the standard value or
seat width is not uniform, reface the seat using the seat cutter.
Valve seat width W:
Standard: 0.9 – 1.1 mm
If the valve seat is out of specification, re-cut the seat.
VALVE SEAT SERVICING
• The valve seats 1 for both the intake valve 2 and exhaust
valve 3 are machined to four different angles. The seat con-
tact 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. (
2-7)
15˚
45˚
60˚
30˚
45˚
60˚
INTAKE EXHAUST
Seat angle 30°, 45°, 60° 15°, 45°, 60°
Seat width 0.9 – 1.1 mm 0.9 – 1.1 mm
Valve diameter 27.2 mm 22 mm
Valve guide I.D. 4.000 – 4.012 mm 4.000 – 4.012 mm
* 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.
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