Yamaha 2008 WR450F, Owner'S Service Manual

Page: 116 / 220

5-22
VALVES AND VALVE SPRINGS
REMOVING THE VALVE LIFTER
AND VALVE COTTER
1. Remove:
•
Valve lifter "1"
• Pad "2"
Identify each lifter "1" and pad "2" po-
sition very carefully so that they can
be reinstalled in their original place.
2. Check:
• Valve sealing
Leakage at the valve seat
→
In-
spect the valve face, valve seat
and valve seat width.
Checking steps:
a. Pour a clean solvent "1" into the
intake and exhaust ports.
b. Check that the valve seals prop-
erly.
There should be no leakage at the
valve seat "2".
3. Remove:
• Valve cotter
Attach a valve spring compressor "1"
between the valve spring retainer and
the cylinder head to remove the valve
cotters.
CHECKING THE VALVE
1. Measure:
• Stem-to-guide clearance
Out of specification
→
Replace
the valve guide.
2. Replace:
•
Valve guide
Replacement steps:
To ease guide removal, installation
and to maintain correct fit heat the
cylinder head in an over to 100 °C
(212 °F).
a. Remove the valve guide using a
valve guide remover "1".
b. Install the new valve guide using a
valve guide remover "1" and valve
guide installer "2".
c. After installing the valve guide,
bore the valve guide using a valve
guide reamer "3" to obtain proper
stem-to-guide clearance.
After replacing the valve guide reface
the valve seat.
3. Inspect:
• Valve face
Pitting/wear
→
Grind the face.
• Valve stem end
Mushroom shape or diameter
larger than the body of the stem
→
Replace.
4. Measure:
•
Margin thickness "a"
Valve spring compres-
sor:
YM-4019/90890-04019
Stem-to-guide clearance = valve
guide inside diameter "a" -
valve stem diameter "b"
Clearance (stem to
guide):
Intake:
0.010–0.037 mm
(0.0004–0.0015 in)
<Limit>:0.08 mm
(0.003 in)
Exhaust:
0.020–0.047 mm
(0.0008–0.0019 in)
<Limit>:0.10 mm
(0.004 in)
Valve guide remover:
Intake:4.5 mm (0.18 in)
YM-4116/90890-04116
Exhaust:5.0 mm (0.20
in)
YM-4097/90890-04097
Valve guide installer:
Intake:
YM-4117/90890-04117
Exhaust:
YM-4098/90890-04098
Valve guide reamer:
Intake:4.5 mm (0.18 in)
YM-4118/90890-04118
Exhaust:5.0 mm (0.20
in)
YM-4099/90890-04099