Yamaha F30B 2018, Service Manual

Page: 191 / 348

7-36
Camshaft and valve
Checking the valve seat
1. Measure:
• Contact width “a”
Not seated properly/out of specification

Reface.
Uneven

Check the valve guide.
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a. Remove carbon deposits from the valve.
b. Apply a thin, even layer of blue layout fluid
(Dykem) onto the valve seat.
c. Push the valve lightly against the valve
seat using the special service tool “1”.
d. Measure the valve seat contact width “a”
where the blue layout fluid is adhered to
the valve face.
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Refacing the valve seat
After every lapping procedure, make sure
to clean off any remaining lapping com-
pound from the cylinder head and valves.
1. Reface:
• Valve seat
Seat contact width IN
1.20–1.60 mm (0.0472–0.0630
in)
Limit
2.050 mm (0.0807 in)
Seat contact width EX
1.20–1.60 mm (0.0472–0.0630
in)
Limit
2.050 mm (0.0807 in)
a
Valve lapper “1”
90890-04101
Valve lapping tool “1”
YM-A8998
1
60 45 30
A
45
45
30
30
60
B