Yamaha F90D, Service Manual

Page: 95 / 241

POWR
Power unit
5-29
6D81G11
2. Install the new valve guide
2
by striking
the special tool from the camshaft side to
the specified position
a
.
NOTE:
• Before installing the valve guide, mark its
installation position
b
as shown.
• Apply engine oil to the surface of the new
valve guide.
3. Insert the special service tool into the
valve guide
2
, and then ream the valve
guide.
NOTE:
• Turn the valve guide reamer clockwise to
ream the valve guide.
• Do not turn the reamer counterclockwise
when removing the reamer.
4. Measure the valve guide inside diameter.
Checking the valve seat
1. Eliminate carbon deposits from the valve
with a scraper.
2. Apply a thin, even layer of Mechanic’s
blueing dye (Dykem) onto the valve seat.
3. Lap the valve slowly on the valve seat
with a valve lapper (commercially avail-
able) as shown.
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 is uneven.
Valve guide remover/installer:
YM-04064-A
Valve guide position
a
:
11.5
±
0.2 mm (0.45
±
0.01 in)
Valve guide reamer: YM-04066
Valve guide inside diameter:
Intake and exhaust:
6.000–6.018 mm
(0.2362–0.2369 in)