oil YAMAHA YZ450F 2003 Service Manual

3 - 21
INSP
ADJ
VALVE CLEARANCE ADJUSTMENT
Round off the last digit of the installed pad
number to the nearest increment.
Last digit of pad
numberRounded value
0, 1 or 2 0
4, 5 or 6 5
8 or 9 10
EXAMPLE:
Installed pad number = 148
Rounded off value = 150
NOTE:
Pads can only be selected in 0.05 mm incre-
ments.
Locate the rounded-off value and the mea-
sured valve clearance in the chart “PAD
SELECTION TABLE”. The field where
these two coordinates intersect shows the
new pad number to use.
NOTE:
Use the new pad number only as a guide
when verifying the valve clearance adjust-
ment.
Install the new pads 5 and the valve lift-
ers 6.
NOTE:
Apply the engine oil on the valve lifters.
Apply the molybdenum disulfide oil on the
valve stem ends.
Valve lifter must turn smoothly when
rotated with a finger.
Be careful to reinstall valve lifters and
pads in their original place.
Install the camshafts (exhaust and intake),
the timing chain and the camshaft caps.
Refer to “CAMSHAFTS” section in the
CHAPTER 4.
T R..
Bolt (camshaft cap):
10 Nm (1.0 m • kg, 7.2 ft • lb)

3 - 31
INSP
ADJ
SPROCKETS INSPECTION/DRIVE CHAIN INSPECTION
EC368000
SPROCKETS INSPECTION
1. Inspect:
Sprocket teeth a
Excessive wear → Replace.
NOTE:
Replace the drive, driven sprockets and drive
chain as a set.
EC369002
DRIVE CHAIN INSPECTION
1. Remove:
Master link clip
Joint 1
Drive chain 2
2. Clean:
Drive chain
Place it in kerosene, and brush off as
much dirt as possible. Then remove the
chain from the kerosene and dry the
chain.
3. Measure:
Drive chain length (10 links) a
Out of specification → Replace.
Drive chain length (10 links):
Limit: 152.5 mm (6.00 in)
4. Check:
Drive chain stiffness a
Clean and oil the chain and hold as
illustrated.
Stiff → Replace drive chain.

3 - 32
INSP
ADJ
DRIVE CHAIN SLACK ADJUSTMENT
5. Install:
Drive chain 1
Joint 2
Master link clip 3
CAUTION:
Be sure to install the master link clip to the
direction as shown.
aTurning direction
6. Lubricate:
Drive chain
Drive chain lubricant:
SAE 10W-30 motor oil or suit-
able chain lubricants
New
DRIVE CHAIN SLACK ADJUSTMENT
1. Elevate the rear wheel by placing the
suitable stand under the engine.
2. Check:
Drive chain slack a
Above the seal guard installation bolt.
Out of specification → Adjust.
NOTE:
Before checking and/or adjusting, rotate the
rear wheel through several revolutions and
check the slack several times to find the tight-
est point. Check and/or adjust chain slack with
rear wheel in this “tight chain” position.
Drive chain slack:
40 ~ 50 mm (1.6 ~ 2.0 in)

3 - 33
INSP
ADJ
FRONT FORK INSPECTION
3. Adjust:
Drive chain slack
Drive chain slack adjustment steps:
Loosen the axle nut 1 and locknuts 2.
Adjust chain slack by turning the adjusters
3.
To tighten → Turn adjuster 3 counter-
clockwise.
To loosen → Turn adjuster 3 clockwise
and push wheel forward.
Turn each adjuster exactly the same
amount to maintain correct axle alignment.
(There are marks a on each side of chain
puller alignment.)
NOTE:
Turn the adjuster so that the chain is in line
with the sprocket, as viewed from the rear.
CAUTION:
Too small chain slack will overload the
engine and other vital parts; keep the
slack within the specified limits.
Tighten the axle nut while pushing down
the drive chain.
T R..
Axle nut:
125 Nm (12.5 m • kg, 90 ft • lb)
Tighten the locknuts.
T R..
Locknut:
16 Nm (1.6 m • kg, 11 ft • lb)
EC36C000
FRONT FORK INSPECTION
1. Inspect:
Front fork smooth action
Operate the front brake and stroke the
front fork.
Unsmooth action/oil leakage → Repair
or replace.

3 - 34
INSP
ADJFRONT FORK OIL SEAL AND DUST SEAL CLEANING/
FRONT FORK INTERNAL PRESSURE RELIEVING/
FRONT FORK REBOUND DAMPING FORCE ADJUSTMENT
EC36D001
FRONT FORK OIL SEAL AND DUST SEAL
CLEANING
1. Remove:
Protector
Dust seal 1
NOTE:
Use a thin screw driver, and be careful not to
damage the inner fork tube and dust seal.
2. Clean:
Dust seal a
Oil seal b
NOTE:
Clean the dust seal and oil seal after every
run.
Apply the lithium soap base grease on the
inner tube.
FRONT FORK INTERNAL PRESSURE
RELIEVING
NOTE:
If the front fork initial movement feels stiff during
a run, relieve the front fork internal pressure.
1. Elevate the front wheel by placing a suit-
able stand under the engine.
2. Remove the air bleed screw 1 and
release the internal pressure from the
front fork.
3. Install:
Air bleed screw
EC36H002
FRONT FORK REBOUND DAMPING FORCE
ADJUSTMENT
1. Adjust:
Rebound damping force
By turning the adjuster 1.
T R..1 Nm (0.1 m · kg, 0.7 ft · lb)
Stiffer a →Increase the rebound damp-
ing force. (Turn the adjuster
1 in.)
Softer b →Decrease the rebound damp-
ing force. (Turn the adjuster
1 out.)

3 - 36
INSP
ADJ
REAR SHOCK ABSORBER INSPECTION
STANDARD POSITION:
This is the position which is back by the spe-
cific number of clicks from the fully turned-in
position.
* For EUROPE
CAUTION:
Do not force the adjuster past the minimum
or maximum extent of adjustment. The
adjuster may be damaged.
WARNING
Always adjust each front fork to the same
setting. Uneven adjustment can cause poor
handling and loss of stability.
3. Install:
Rubber cap
Extent of adjustment:
Maximum Minimum
Fully turned in
position20 clicks out
(from maximum
position)
Standard position:
12 clicks out
* 9 clicks out
EC36K000
REAR SHOCK ABSORBER INSPECTION
1. Inspect:
Swingarm smooth action
Abnormal noise/unsmooth action →
Grease the pivoting points or repair the
pivoting points.
Damage/oil leakage → Replace.

INSP
ADJ
CONTROLE DE PRESSION DES PNEUS/CONTROLE ET SERRAGE DES
RAYONS/CONTROLE DE LA ROUE
REIFENLUFTDRUCK KONTROLLIEREN/SPEICHEN KONTROLLIEREN
UND FESTZIEHEN/RÄDER KONTROLLIEREN
REIFENLUFTDRUCK KONTROLLIEREN
1. Messen:
Reifenluftdruck
Unvorschriftsmäßig → Einstellen.
HINWEIS:
Den Reifenluftdruck bei kalten Reifen kon-
trollieren.
Bei zu niedrigem Reifendruck liegt die Rei-
fenwulst nicht fest an, was dazu führen kann,
daß sich der Reifen von der Felge löst.
Ein geneigter Reifenventilschaft deutet an,
daß der Reifen verrutscht ist.
Bei geneigtem Reifenventilschaft muß die
Reifenposition berichtigt werden.
Standard-Reifenluftdruck
100 kPa (1,0 bar)
SPEICHEN KONTROLLIEREN UND
FESTZIEHEN
1. Kontrollieren:
Speichen 1
Verzug/Beschädigung → Erneuern.
Speichen locker → Nachspannen.
2. Festziehen:
Speichen
HINWEIS:
Die Speichen müssen vor und nach dem Ein-
fahren nachgezogen werden. Nach jeder
Übungsfahrt bzw. Rennen die Speichenspan-
nung prüfen.
T R..3 Nm (0,3 m · kg)
RÄDER KONTROLLIEREN
1. Messen:
Felgenschlag
Das Rad anheben und drehen.
Übermäßig → Erneuern. CONTROLE DE PRESSION DES PNEUS
1. Mesurer:
Pression des pneus
Hors spécification → Régler.
N.B.:
Vérifier le pneu alors qu’il est froid.
Des butées de bourrelet lâches permettent au
pneu de se détacher de sa position sur la jante
lorsque la pression des pneus est basse.
Une tige de soupape de pneu inclinée indique que
le pneu se détache de sa position sur la jante.
Si la tige de soupape de pneu est inclinée, le pneu
a tendance à se détacher de sa position. Corriger
la position du pneu.
Pression des pneus standard:
100 kPa (1,0 kgf/cm2, 15 psi)
CONTROLE ET SERRAGE DES RAYONS
1. Contrôler:
Rayons 1
Déformation/endommagement → Changer.
Rayons desserrés → Resserrer.
2. Serrer:
Rayon
N.B.:
Ne pas oublier de retendre les rayons avant et après
le rodage. Après un entraînement ou une course,
contrôler si les rayons ne sont pas détendus.
T R..3 Nm (0,3 m · kg, 2,2 ft · lb)
CONTROLE DE LA ROUE
1. Mesure:
Voile de roue
Soulever la roue et la tourner.
Voile excessif → Changer.
3 - 41

3 - 44
INSP
ADJ
LUBRICATION
LUBRICATION
To ensure smooth operation of all compo-
nents, lubricate your machine during setup,
after break-in, and after every race.
1All control cable
2Clutch lever pivot
3Shift pedal pivot
4Footrest pivot
5Throttle-to-handlebar contact
6Drive chain
7Tube guide cable winding portion
8Throttle cable end
9Clutch cable end
0Hot starter cable endÅUse Yamaha cable lube or equivalent on these
areas.
ıUse SAE 10W-30 motor oil or suitable chain
lubricants.
ÇLubricate the following areas with high quality,
lightweight lithium-soap base grease.
CAUTION:
Wipe off any excess grease, and avoid get-
ting grease on the brake discs.
AAA
AAB
CC

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

4 - 26
ENGCAMSHAFTS
Decompression system
1. Check:
Decompression system
Checking steps:
Check that the decompressor cam 1
moves smoothly.
Check that the decompressor lever pin 2
projects from the camshaft.
Timing chain tensioner
1. Check:
While pressing the tensioner rod lightly
with fingers, use a thin screwdriver 1
and wind the tensioner rod up fully
clockwise.
When releasing the screwdriver by
pressing lightly with fingers, make sure
that the tensioner rod will come out
smoothly.
If not, replace the tensioner assembly.
ASSEMBLY AND INSTALLATION
1. Install:
Exhaust camshaft 1
Intake camshaft 2
Installation steps:
Turn the crankshaft counterclockwise until
the “I” mark a on the rotor is aligned with
the stationary pointer b on the crankcase
cover.
NOTE:
Apply the molybdenum disulfide oil on the
camshafts.
Apply the engine oil on the decompression
system.