16
(3) Valve seat
a. 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.
b. Correct the seat using a seat cutter of 15°, 45°
and 75° so that the contact width is the standard
assembling value.
Valve seat contact width (mm)
Standard assembling value Repair value
Intake 1.66 – 1.87
2.5
Exhaust 1.66 – 1.73
c. When the seat recess exceeds the service limit,
replace the valve seat or valve.
Valve seat recess (mm)
Standard assembling value Service limit
0.85 – 1.15 1.8
d. Coat the valve seat surface with compound and
lap the contact surface turning the valve.
e. Check that the valve contact surface is within the
standard value and the contact position is even.
019X
020X
021X
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