2003 YAMAHA WR 450F head

4 - 23
ENGCAMSHAFTS
REMOVAL POINTS
Camshaft
1. Remove:
Timing plug 1
Straight plug 2
2. Align:
“I” mark
With stationary pointer.
Checking steps:
Turn the crankshaft counterclockwise with
a wrench.
Align the “I” mark a on the rotor with the
stationary pointer b on the crankcase
cover. When the “I” mark is aligned with
the stationary pointer, the piston is at the
Top Dead Center (T.D.C.).
NOTE:
In order to be sure that the piston is at Top
Dead Center, the punch mark c on the
exhaust camshaft and the punch mark d
on the intake camshaft must align with the
cylinder head surface, as shown in the
illustration.
If there is no clearance, rotate the crank-
shaft counterclockwise one turn.
1
2
b
a
3. Loosen:
Tensioner cap bolt 1
4. Remove:
Timing chain tensioner 2
5. Remove:
Bolt (camshaft cap) 1
Camshaft caps 2
NOTE:
Remove the bolts (camshaft cap) in a criss-
cross pattern, working from the outside in.
CAUTION:
The bolts (camshaft cap) must be removed
evenly to prevent damage to the cylinder
head, camshafts or camshaft caps.
1
2
1
2

4 - 25
ENGCAMSHAFTS
4. Measure:
Camshaft-to-cap clearance
Out of specification → Measure cam-
shaft journal diameter.
Camshaft-to-cap clearance:
0.020 ~ 0.054 mm
(0.0008 ~ 0.0021 in)
: 0.08 mm (0.003 in)
Measurement steps:
Install the camshaft onto the cylinder
head.
Position a strip of Plastigauge® 1 onto the
camshaft.
Install the circlip, dowel pins and camshaft
caps.
T R..
Bolt (camshaft cap):
10 Nm (1.0 m • kg, 7.2 ft • lb)
NOTE:
Tighten the bolts (camshaft cap) in a criss-
cross pattern from innermost to outer
caps.
Do not turn the camshaft when measuring
clearance with the Plastigauge®.
Remove the camshaft caps and measure
the width of the Plastigauge
® 1.
5. Measure:
Camshaft journal diameter a
Out of specification → Replace the
camshaft.
Within specification → Replace cam-
shaft case and camshaft caps as a set.
Camshaft sprocket
1. Inspect:
Camshaft sprocket 1
Wear/damage → Replace the camshaft
assembly and timing chain as a set.
Camshaft journal diameter:
21.967 ~ 21.980 mm
(0.8648 ~ 0.8654 in)

4 - 27
ENGCAMSHAFTS
Fit the timing chain 3 onto both camshaft
sprockets and install the camshafts on the
cylinder head.
NOTE:
The camshafts should be installed onto the
cylinder head so that the exhaust cam
sprocket punch mark c and the intake cam
sprocket punch mark d align with the sur-
face of the cylinder head.
CAUTION:
Do not turn the crankshaft during the
camshaft installation. Damage or
improper valve timing will result.
Install the clips and camshaft caps 4.
T R..
Bolt (camshaft cap):
10 Nm (1.0 m • kg, 7.2 ft • lb)
NOTE:
Apply the engine oil on the thread and con-
tact surface of the bolts (camshaft cap) 5.
Tighten the bolts (camshaft cap) in a criss-
cross pattern.
CAUTION:
The bolts (camshaft cap) must be tight-
ened evenly, or damage to the cylinder
head, camshaft caps, and camshaft will
result.
5
4
E
2. Install:
Timing chain tensioner
Installation steps:
While pressing the tensioner rod lightly
with fingers, use a thin screwdriver and
wind the tensioner rod up fully clockwise.

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

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
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

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 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.

4 - 31
ENG

CYLINDER 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)

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 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