Yamaha F50A - Checking the Valve Seat

62Y3A11
5-42
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2. Install the new valve guide
2
by striking
the special service tool from the cam-
shaft side until the valve guide clip
3
contacts the cylinder head.
NOTE:
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.
Replace the valve guide if out of specifi-
cation.
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 obtain-
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: YM-01122
Valve guide remover/installer:
90890-06801
Valve guide reamer:
YM-01196 / 90890-06804
Valve guide inside diameter:
5.50–5.51 mm (0.2165–0.2169 in)
Cylinder head