Replacing The Valve Guide; Checking The Valve Seat - Yamaha F4B Service Manual

Valve guide inside diameter a:
Intake and exhaust:
5.500–5.512 mm (0.2165–0.2170 in)
2. Calculate the valve guide clearance.
Replace the valve guide if out of
specification.
Valve guide clearance:
Intake:
0.010–0.037 mm (0.0004–0.0015 in)
Exhaust:
0.025–0.052 mm (0.0010–0.0020 in)

Replacing the valve guide

After replacing the valve guide, check the
valve seat contact area.
1. Remove the valve guide a from the com-
bustion chamber side using the special
service tool b.
a
Valve guide remover/installer b:
90890-06801
2. Install a new valve guide c from the
rocker arm side
installation height a using the special
service tool b.
b
b
to the specified
a
c
Valve guide remover/installer b:
90890-06801
Valve guide installation height a:
8.2–9.1 mm (0.32–0.36 in)
3. Insert the special service tool d into the
valve guide c, and then ream the valve
guide.
c
Valve guide reamer d: 90890-06804
TIP:
• Turn the valve guide reamer clockwise to
ream the valve guide.
• Do not turn the valve guide reamer counter-
clockwise when removing it.
• Make sure to clean the valve guide after
reaming it.
4. Measure the valve guide inside diameter.
Valve guide inside diameter:
Intake and exhaust:
5.500–5.512 mm (0.2165–0.2170 in)

Checking the valve seat

1. Remove carbon deposits from the valves.
2. Apply a thin, even layer of Mechanic's
blueing dye (Dykem) onto the valve seat.
3. Press the valve lightly against the valve
seat using the special service tool a.
Cylinder head
0
1
d
2
3
4
5
6
7
8
9
10
A
7-32