Yamaha F200B, Service Manual

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7-63
POWR
Power unit
3. Measure the valve stem diameter
b
.
Replace if out of specification.
4. Measure the valve stem runout. Replace
if above specification.
Checking the valve guide
Before checking the valve guides, make sure
that the valve stem diameter is within specifi-
cation.
1. Measure the valve guide inside diameter
a
.
2. Calculate the valve guide clearance as
follows. Replace the valve guide if out of
specification.
Replacing the valve guide
Do not reuse a valve guide, always
replace it with a new one.
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.
Valve margin thickness
a
:
Intake:
0.500–0.900 mm (0.0197–0.0354 in)
Exhaust:
0.900–1.300 mm (0.0354–0.0512 in)
Valve stem diameter
b
:
Intake:
5.477–5.492 mm (0.2156–0.2162 in)
Exhaust:
5.464–5.479 mm (0.2151–0.2157 in)
Valve stem runout:
Intake and exhaust:
0.010 mm (0.0004 in)
b
Valve guide inside diameter
a
:
Intake and exhaust:
5.504–5.522 mm (0.2167–0.2174 in)
Valve guide clearance = valve guide inside
diameter – valve stem diameter:
Intake:
0.012–0.045 mm (0.0005–0.0018 in)
Exhaust:
0.025–0.058 mm (0.0010–0.0023 in)
Valve guide remover/installer
2
:
90890-06801
a
1
2