Yamaha F50D Servise Manual - page 175
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A
Checking the valve guide
Before checking a valve guide, make sure
that the valve stem diameter is within specifi-
cation.
1.
Measure the valve guide inside diameter
a
. Replace if out of specification.
2.
Calculate the valve stem-to-valve guide
clearance. Replace the valve guide if out
of specification.
Replacing the valve guide
After replacing a valve guide, check the valve
seat contact area.
1.
Remove the valve guide
1
using the
special service tool
2
from the combus-
tion chamber side.
2.
Install a new valve guide
3
using the
special service tool
2
from the camshaft
side until the valve guide clip
4
contacts
the cylinder head.
TIP:
Apply engine oil to the surface of new valve
guides.
3.
Insert the special service tool
5
into the
valve guide
3
, and then ream the valve
guide.
Valve stem runout:
Intake: 0.030 mm (0.0012 in)
Exhaust: 0.030 mm (0.0012 in)
Valve guide inside diameter
a
:
5.500–5.512 mm (0.2165–0.2170 in)
Valve stem-to-valve guide clearance =
valve guide inside diameter – valve stem
diameter:
Intake:
0.010–0.037 mm (0.0004–0.0015 in)
Exhaust:
0.025–0.052 mm (0.0010–0.0020 in)
a
Valve guide remover/installer
2
:
90890-06801
Valve guide remover/installer
2
:
90890-06801
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2
3
2
4
Camshaft and valve