Yamaha Wr 450 F Owners Manual

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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. Check:
Rotor “I” mark
Align with the crankcase stationary
pointer.
Camshaft match marks
Align with the cylinder head surface.
Out of alignment → Adjust.
CAMSHAFTS 
						

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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
Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE 
COVERS” section.
Exhaust pipe and silencer Refer to “EXHAUST PIPE AND 
SILENCER” section.
Radiator Refer to “RADIATOR” section.
Carburetor Refer to “CARBURETOR” section.
Camshaft Refer to “CAMSHAFTS” section.
1 Oil delivery pipe  1
2 Nut 2
3* Bolt (L = 150 mm) 2
Refer to NOTE.
4* Bolt (L = 160 mm) 2
5 Cylinder head 1
6 Gasket 1
7 Dowel pin 2
8 Timing chain guide (front) 1
1 
						

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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 the cylinder head.
Use a feeler gauge to measure the
warpage.
If the warpage is out of specification,
resurface the cylinder head.
Place a 400 ~ 600 grit wet sandpaper on
the surface plate, and resurface the head
using a figure-eight sanding pattern.
NOTE:
To ensure an even surface rotate the cylin-
der head several times. 
						

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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
the bolts, the contact surfaces of the plain
washers, the contact surface of the cylin-
der head, and the threads of the crank-
case.
Apply the molybdenum disulfide grease on
the threads and contact surfaces of the
bolts and on both contact surfaces of the
plain washers.
Install the plain washers and bolts.
Tighten the bolts to the specified torque in
two or three steps in the proper tightening
sequence as shown.
T R..
Bolts (cylinder head):
1st: 
30 Nm (3.0 m • kg, 22 ft • lb) 
						

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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 the two
steps to reach the specified angle of 180˚ in
the proper tightening sequence as shown.
T R..
Bolts (cylinder head):
Final: 
Specified angle 180˚
1
2
180˚
3. Install:
Nut (cylinder head) 1
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
4. Install:
Copper washer 1 
Oil delivery pipe 2
Union bolt (M8) 3 
Union bolt (M10) 4
New
T R..18 Nm (1.8 m · kg, 13 ft · lb)
T R..20 Nm (2.0 m · kg, 14 ft · lb)
CYLINDER HEAD 
						

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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
NOTE:
Attach a valve spring compressor 1 between
the valve spring retainer and the cylinder head
to remove the valve cotters.
Valve spring compressor:
YM-4019/90890-04019 
						

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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 cylinder head in
an over to 100 ˚C (212 ˚F).
Remove the valve guide using a valve
guide remover 1.
Install the new valve guide using a valve
guide remover 1 and valve guide installer
2.
After installing the valve guide, bore the
valve guide using a valve guide reamer 3
to obtain proper stem-to-guide clearance. 
						

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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 the body of the stem → Replace.
4. Measure:
Margin thickness a 
Out of specification → Replace.
Margin thickness:
Intake:
1.0 mm (0.039 in)
: 0.85 mm (0.033 in)
Exhaust:
1.0 mm (0.039 in)
: 0.85 mm (0.033 in) 
						

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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 (0.0354 ~ 0.0433 in)
: 1.6 mm (0.0630 in)
Exhaust:
0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)
: 1.6 mm (0.0630 in)
Measurement steps:
Apply Mechanic’s blueing dye (Dykem) b
to the valve face.
Install the valve into the cylinder head.
Press the valve through the valve guide
and onto the valve seat to make a clear
pattern.
Measure the valve seat width. Where the
valve seat and valve face made contact,
blueing will have been removed.
If the valve seat is too wide, too narrow, or
the seat is not centered, the valve seat
must be refaced.