2003 YAMAHA WR 450F head

3 - 20
INSP
ADJ
VALVE CLEARANCE ADJUSTMENT
4. Check:
Valve clearance
Out of specification → Adjust.
Valve clearance (cold):
Intake valve:
0.10 ~ 0.15 mm
(0.0039 ~ 0.0059 in)
Exhaust valve:
0.20 ~ 0.25 mm
(0.0079 ~ 0.0098 in)
Checking steps:
Turn the crankshaft counterclockwise with
a wrench.
Align the T.D.C. mark a on the rotor with
the align mark b on the crankcase cover
when piston is at T.D.C. on compression
stroke.
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 cyl-
inder head surface, as shown in the illustra-
tion.
Measure the valve clearance e using a
feeler gauge 1.
NOTE:
Record the measured reading if the clear-
ance is incorrect.
b
a

3 - 45
INSP
ADJ
STEERING HEAD INSPECTION AND ADJUSTMENT
2. Inspect:
Bearing free play
Exist play → Replace.
STEERING HEAD INSPECTION AND
ADJUSTMENT
1. Elevate the front wheel by placing a suit-
able stand under the engine.
2. Check:
Steering shaft
Grasp the bottom of the forks and gen-
tly rock the fork assembly back and
forth.
Free play → Adjust steering head.
3. Check:
Steering smooth action
Turn the handlebar lock to lock.
Unsmooth action → Adjust steering ring
nut.
4. Adjust:
Steering ring nut
Steering ring nut adjustment steps:
Remove the headlight.
Remove the handlebar and handle crown.
Loosen the ring nut 1 using the ring nut
wrench 2.
Ring nut wrench:
YU-33975/90890-01403

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INSP
ADJ
STEERING HEAD INSPECTION AND ADJUSTMENT
Tighten the ring nut 3 using ring nut
wrench 4.
NOTE:
Set the torque wrench to the ring nut wrench
so that they form a right angle.
Ring nut wrench:
YU-33975/90890-01403
T R..
Ring nut (initial tightening):
38 Nm (3.8 m • kg, 27 ft • lb)
Loosen the ring nut one turn.
Retighten the ring nut using the ring nut
wrench.
WARNING
Avoid over-tightening.
T R..
Ring nut (final tightening):
7 Nm (0.7 m • kg, 5.1 ft • lb)
Check the steering shaft by turning it lock
to lock. If there is any binding, remove the
steering shaft assembly and inspect the
steering bearings.
Install the plain washer 5, handle crown
6, plain washer 7, steering shaft nut 8,
steering shaft cap 9, handlebar 0, han-
dlebar holder A and headlight B.
NOTE:
The handlebar holder should be installed
with the punched mark a forward.
Insert the end of the fuel breather hose C
into the hole in the steering shaft cap.
CAUTION:
First tighten the bolts on the front side of
the handlebar holder, and then tighten
the bolts on the rear side.
T R..
Steering shaft nut:
145 Nm (14.5 m • kg, 105 ft • lb)
Handlebar holder:
28 Nm (2.8 m • kg, 20 ft • lb)
Pinch bolt (handle crown):
23 Nm (2.3 m • kg, 17 ft • lb)
Headlight (left and right):
10 Nm (1.0 m • kg, 7.2 ft • lb)
Headlight (lower):
7 Nm (0.7 m • kg, 5.1 ft • lb)

3 - 57
INSP
ADJ
REPLACING THE HEADLIGHT BULBS
3. Replace:
Blown fuse
WARNING
Never use a fuse with an amperage rating
other than that specified. Improvising or
using a fuse with the wrong amperage rat-
ing may cause extensive damage to the
electrical system, cause the starting and
ignition systems to malfunction and could
possibly cause a fire.
4. Install:
Fuse cover
Seat Replacement steps:
Set the main switch to “OFF”.
Install a new fuse of the correct amperage.
Set on the switches to verify if the electri-
cal circuit is operational.
If the fuse immediately blows again, check
the electrical circuit.
ItemsAmperage
ratingQ’ty
Main fuse 10 A 1
REPLACING THE HEADLIGHT BULBS
1. Remove:
Headlight
Refer to “SEAT, FUEL TANK AND
SIDE COVERS” section in the CHAP-
TER 4.
2. Remove:
Headlight bulb holder cover 1
3. Detach:
Headlight bulb holder 1
4. Remove:
Headlight bulb 2
WARNING
Since the headlight bulb gets extremely
hot, keep flammable products and your
hands away from the bulb unit it has cooled
down.

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INSP
ADJ
ADJUSTING THE HEADLIGHT BEAMS
5. Install:
Headlight bulb
Secure the new headlight bulb with the
headlight bulb holder.
CAUTION:
Avoid touching the glass part of the head-
light bulb to keep it free form oil, otherwise
the transparency of the glass, the life of the
bulb and the luminous flux will be
adversely affected. If the headlight bulb
gets soiled, thoroughly clean it with a cloth
moistened with alcohol or lacquer thinner.
6. Attach:
Headlight bulb holder
7. Install:
Headlight bulb holder cover
8. Install:
Headlight
Refer to “SEAT, FUEL TANK AND
SIDE COVERS” section in the CHAP-
TER 4.
New
T R..7 Nm (0.7 m · kg, 5.1 ft · lb)
ADJUSTING THE HEADLIGHT BEAMS
1. Adjust:
Headlight beam (vertically)
Adjusting steps:
Turn the adjusting screw 1 in direction a
or b.
Direction a Headlight beam is raised.
Direction b Headlight beam is lowered.

4 - 1
ENG

EC400000
ENGINE
EC4R0000
SEAT, FUEL TANK AND SIDE COVERS
Extent of removal:
1
Seat removal
2
Fuel tank removal
3
Side covers removal
4
Headlight removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removal
SEAT, FUEL TANK AND SIDE
COVERS REMOVAL
Turn the fuel cock to “OFF”.
Disconnect the fuel hose.
1 Seat 1
2 Air scoop (left and right) 2
3 Fitting band 1 Remove on fuel tank side.
4 Bolt (fuel tank) 2
5 Fuel tank 1
6 Side cover (left) 1
Refer to “REMOVAL POINTS”.
7 Side cover (right) 1
8 Headlight coupler 1
9 Headlight 1
13
2
3
4

SEAT, FUEL TANK AND SIDE COVERS

4 - 19
ENGCARBURETOR
Accelerator pump timing adjustment
Adjustment steps:
NOTE:
In order for the throttle valve height a to
achieve the specified value, tuck under the
throttle valve plate 1 the rod 2 etc. with
the same outer diameter as the specified
value.
Throttle valve height:
3.1 mm (0.122 in)
Fully turn in the accelerator pump adjust-
ing screw 3.
Check that the link lever 4 has free play
b by pushing lightly on it.
Gradually turn out the adjusting screw
while moving the link lever until it has no
more free play.
Carburetor installation
1. Install:
Carburetor joint 1
NOTE:
Install the projection a on the cylinder head
between the carburetor joint slots b.
T R..3 Nm (0.3 m · kg, 2.2 ft · lb)
2. Install:
Carburetor 1
NOTE:
Install the projection a between the carburetor
joint slots.
3. Install:
Hot starter plunger 1
1
T R..2 Nm (0.2 m · kg, 1.4 ft · lb)

4 - 21
ENGCAMSHAFTS
CAMSHAFTS
CYLINDER HEAD COVER
Extent of removal:1 Cylinder head cover removal
Extent of removal Order Part name Q’ty Remarks
CYLINDER HEAD COVER
REMOVAL
Preparation for removal Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section.
Carburetor Refer to “CARBURETOR” section.
1 Spark plug 1
2 Engine upper bracket (right) 1
3 Engine upper bracket (left) 1
4 Cylinder head breather hose 1
5 Oil tank breather hose 1
6 Bolt (cylinder head cover) 2
7 Cylinder head cover 1
8 Gasket 1
9 Timing chain guide (upper) 1
1