Checking The Valve Seat; Refacing The Valve Seat - Yamaha F150B Service Manual

POWR
4. Measure the valve guide inside diameter.
Valve guide inside diameter:
5.504–5.522 mm
(0.2167–0.2174 in)

Checking the valve seat

1. Eliminate carbon deposits from the
valves.
2. Apply a thin, even layer of Mechanic's
blueing dye (Dykem) onto the valve
seats.
3. Lap the valve slowly on the valve seat
with a special service tool a.
Valve lapper a: 90890-04101
4. Measure the valve seat contact width a
where the blueing dye is adhered to the
valve face. Reface the valve seat if the
valve is not seated properly or if the valve
seat contact width is out of specification.
Replace the valve guide if the valve seat
contact width is uneven.
a
7-41
Power unit
a
Valve seat contact width a:
Intake:
1.10–1.40 mm (0.043–0.055 in)
Exhaust:
1.40–1.70 mm (0.055–0.067 in)

Refacing the valve seat

After every lapping procedure, make sure to
clean off any remaining lapping compound
from the cylinder head and the valves.
1. Reface the valve seats with the valve
seat cutters.
30 45
Valve seat cutter holder: 90890-06316
Valve seat cutter:
30° (intake): 90890-06817
30° (exhaust): 90890-06326
45° (intake): 90890-06816
45° (exhaust): 90890-06325
60° (intake and exhaust): 90890-06324
60