Checking The Valve Seat; Refacing The Valve Seat - Yamaha F150A Service Manual

TIP:
• To ream the valve guide, turn the valve
guide reamer clockwise.
• When removing the valve guide reamer, do
not turn it counterclockwise.
• After reaming the valve guide, make sure to
clean it.
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Valve guide reamer "1": 90890-06804
4. Measure the valve guide inside diameter.
Valve guide inside diameter:
Intake and exhaust:
5.504–5.522 mm (0.2167–0.2174 in)

Checking the valve seat

1. Remove carbon deposits from the valve.
2. Apply a thin, even layer of Mechanic's
blueing dye (Dykem) onto the valve seat.
3. Push the valve lightly against the valve
seat using the special service tool "1".
Valve lapper "1": 90890-04101
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1
7-43
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.
Check the valve guide if the valve seat
contact width is uneven.
a
Valve seat contact width "a":
Intake:
1.10–1.40 mm (0.0433–0.0551 in)
Exhaust:
1.40–1.70 mm (0.0551–0.0669 in)

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 the valve seat using the valve
seat cutters.
Cylinder head
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