2003 YAMAHA YZ450F oil

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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

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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.

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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.

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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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ENG
CULASSE
ZYLINDERKOPF
PRÜFUNG
Zylinderkopf
1. Entfernen:
Ölkohleablagerungen (im Brennraum)
Einen abgerundeten Schaber verwen-
den.
HINWEIS:
Keine scharfkantigen Gegenstände benutzen,
um Beschädigungen und Kratzer an folgenden
Stellen zu vermeiden:
Zündkerzenbohrung
Ventilsitze
2. Kontrollieren:
Zylinderkopf
Kratzer/Beschädigungen → Erneuern.
3. Messen:
Zylinderkopf-Verzug
Grenzwert überschritten → Planschlei-
fen.
Zylinderkopf-Verzugsgrenze
unter 0,05 mm
Arbeitsschritte
Lineal und Fühlerlehre über den Zylinder-
kopf legen.
Verzug mit der Fühlerlehre messen.
Ist die Verzugsgrenze überschritten, den
Zylinderkopf planschleifen.
Den Zylinderkopf mit Naßschleifpapier (Kör-
nung 400–600) auf einer planen Platte in
einer Achterbewegung abschleifen.
HINWEIS:
Den Zylinderkopf mehrmals drehen, um
eine ebene Oberfläche zu gewährleisten.
CONTROLE
Culasse
1. Eliminer:
Dépôt de calamine
(de la chambre de combustion)
Utiliser un grattoir arrondi.
N.B.:
Ne pas utiliser d’instrument pointu pour éviter
d’endommager ou de rayer:
Filets de bougies
Sièges de soupape
2. Contrôler:
Culasse
Rayures/endommagement → Remplacer.
3. Mesurer:
Déformation de la culasse
Hors spécifications → Surfacer.
Limite de déformation de la culasse:
Moins de 0,05 mm (0,002 in)
Etapes de la mesure de la limite de déforma-
tion et du surfaçage:
Placer une règle et une jauge d’épaisseur sur la
culasse.
Utiliser une jauge d’épaisseur pour mesurer la
déformation.
Si la déformation est hors spécifications, surfa-
cer la culasse.
Mettre un morceau de toile émeri n˚ 400 à 600
humide sur une plaque à surfacer et surfacer la
culasse en décrivant des “huit”.
N.B.:
Tourner la culasse plusieurs fois pour obtenir
une surface lisse.

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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
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.

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ENGVALVES AND VALVE SPRINGS
9. Lap:
Valve face
Valve seat
NOTE:
After refacing the valve seat or replacing the
valve and valve guide, the valve seat and
valve face should be lapped.
Lapping steps:
Apply a coarse lapping compound to the
valve face.
CAUTION:
Do not let the compound enter the gap
between the valve stem and the guide.
Apply molybdenum disulfide oil to the
valve stem.
Install the valve into the cylinder head.
Turn the valve until the valve face and
valve seat are evenly polished, then clean
off all of the compound.
NOTE:
For best lapping results, lightly tap the valve
seat while rotating the valve back and forth
between your hands.
Apply a fine lapping compound to the
valve face and repeat the above steps.
NOTE:
After every lapping operation be sure to
clean off all of the compound from the valve
face and valve seat.
Apply Mechanic’s blueing dye (Dykem) 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 again. If the
valve seat width is out of specification,
reface and relap the valve seat.