Yamaha Wr 450 F Owners Manual

4 - 28
ENG
With the rod fully wound and the chain
tensioner UP mark a facing upward,
install the gasket 1 and the chain ten-
sioner 2, and tighten the bolt 3 to the
specified torque.
T R..
Bolt (timing chain tensioner):
10 Nm (1.0 m • kg, 7.2 ft • lb)
Release the screwdriver, check the ten-
sioner rod to come out and tighten the
gasket 4 and the cap bolt 5 to the speci-
fied torque.
T R..
Tensioner cap bolt:
7 Nm (0.7 m • kg, 5.1 ft • lb)
5
4New
3. Turn:
Crankshaft
Counterclockwise several turns
4....

4 - 29
ENGCYLINDER HEAD
CYLINDER HEAD
CYLINDER HEAD
Extent of removal:1 Cylinder head removal
NOTE:
Tighten the cylinder head bolts to 30 Nm (3.0 m · kg, 22 ft · lb) in the proper tightening sequence, remove and
retighten the cylinder head bolts to 20 Nm (2.0 m · kg, 14 ft · lb) in the proper tightening sequence, and then
tighten the cylinder head bolts further to reach the specified angle 180˚ in the proper tightening sequence.
Extent of removal Order Part name Q’ty Remarks
CYLINDER HEAD REMOVAL...

4 - 30
ENGCYLINDER HEAD
INSPECTION
Cylinder head
1. Eliminate:
Carbon deposits (from the combustion
chambers)
Use a rounded scraper.
NOTE:
Do not use a sharp instrument to avoid dam-
aging or scratching:
Spark plug threads
Valve seats
2. Inspect:
Cylinder head
Scratches/damage → Replace.
3. Measure:
Cylinder head warpage
Out of specification → Resurface.
Cylinder head warpage:
Less than 0.05 mm (0.002 in)
Warpage measurement and resurface-
ment steps:
Place a straightedge and a feeler gauge
across...

4 - 31
ENGCYLINDER HEAD
ASSEMBLY AND INSTALLATION
1. Install:
Timing chain guide (front) 1
Dowel pin 2
Cylinder head gasket 3 
Cylinder head 4
NOTE:
While pulling up the timing chain, install the
timing chain guide (front) and cylinder head.
New
2. Install:
Plain washer 1
Bolt [L=160 mm (6.30 in)] 2
Bolt [L=150 mm (5.91 in)] 3
 Installation steps:
CAUTION:
Tighten the cylinder head using the rota-
tion angle procedure to obtain uniform
tightening torque.
Wash the threads and contact surfaces of...

4 - 32
ENG
Remove the bolts.
Again apply the molybdenum disulfide
grease on the threads and contact sur-
faces of the bolts and on both contact sur-
faces of the plain washers.
Retighten the bolts.
NOTE:
Tighten the bolts to the specified torque in
two or three steps in the proper tightening
sequence as shown.
T R..
Bolts (cylinder head):
2nd: 
20 Nm (2.0 m • kg, 14 ft • lb)
Put a mark on the corner 1 of the bolt
(cylinder head) and the cylinder head 2
as shown.
NOTE:
Tighten the bolts 90˚ in each of...

4 - 33
ENGVALVES AND VALVE SPRINGS
VALVES AND VALVE SPRINGS
VALVES AND VALVE SPRINGS
Extent of removal:1 Valve removal
Extent of removal Order Part name Q’ty Remarks
VALVES AND VALVE SPRINGS 
REMOVAL
Preparation for removal Cylinder head Refer to “CYLINDER HEAD” section.
1 Valve lifter 5
Use special tool.
Refer to “REMOVAL POINTS”. 2 Adjusting pad 5
3 Valve cotter 10
4 Valve retainer 5
5 Valve spring 5
6 Stem seal 5
7 Valve spring seat 5
8 Exhaust valve 2
9 Intake valve 3
1 

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ENGVALVES AND VALVE SPRINGS
REMOVAL POINTS
1. Remove: 
Valve lifters 1 
Pads 2 
NOTE:
Identify each lifter 1 and pad 2 position very
carefully so that they can be reinstalled in their
original place.
2. Check:
Valve sealing
Leakage at the valve seat → Inspect
the valve face, valve seat and valve
seat width.
Checking steps:
Pour a clean solvent 1 into the intake and
exhaust ports.
Check that the valve seals properly.
There should be no leakage at the valve
seat 2.
3. Remove:
Valve cotters...

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ENGVALVES AND VALVE SPRINGS
INSPECTION
Valve
1. Measure:
Stem-to-guide clearance
Out of specification → Replace the
valve guide. 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)
: 0.08 mm (0.003 in)
Exhaust:
0.020 ~ 0.047 mm 
(0.0008 ~ 0.0019 in)
: 0.10 mm (0.004 in)
2. Replace:
Valve guide
Replacement steps:
NOTE:
To ease guide removal, installation and to
maintain correct fit heat the...

4 - 36
ENGVALVES AND VALVE SPRINGS
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
NOTE:
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...

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ENGVALVES AND VALVE SPRINGS
5. Measure:
Runout (valve stem)
Out of specification → Replace.
NOTE:
When installing a new valve always replace
the guide.
If the valve is removed or replaced always
replace the oil seal.
6. Eliminate:
Carbon deposits
(from the valve face and valve seat)
7. Inspect:
Valve seats
Pitting/wear → Reface the valve seat.
Runout limit:
0.01 mm (0.0004 in)
8. Measure:
Valve seat width a 
Out of specification → Reface the valve
seat.
Valve seat width:
Intake:
0.9 ~ 1.1 mm...