2003 YAMAHA YZ450F fuel

SPEC
2 - 16
MAINTENANCE SPECIFICATIONS
NOTE:
- marked portion shall be checked for torque tightening after break-in or before each race.Part to be tightened Thread size Q’tyTightening torque
Nm m·kg ft·lb
Rear wheel axle and nut M20 × 1.5 1 125 12.5 90
Driven sprocket and wheel hub M8 × 1.25 6 42 4.2 30
Nipple (spoke)–72 3 0.3 2.2
Disc cover and rear brake caliper M6 × 1.0 2 7 0.7 5.1
Protector and rear brake caliper M6 × 1.0 2 7 0.7 5.1
Chain puller adjust bolt and locknut M8 × 1.25 2 16 1.6 11
Engine mounting:
Engine upper bracket and frame M10 × 1.25 2 55 5.5 40
Engine lower bracket and frame M8 × 1.25 4 34 3.4 24
Engine and frame (front) M10 × 1.25 1 65 6.5 47
Engine and frame (upper) M10 × 1.25 1 55 5.5 40
Engine and frame (lower) M10 × 1.25 1 69 6.9 50
Engine guard (lower) M8 × 1.25 1 23 2.3 17
Engine skid plate mounting M6 × 1.0 6 10 1.0 7.2
CDI unit bracket mounting M6 × 1.0 1 10 1.0 7.2
Pivot shaft and nut M16 × 1.5 1 85 8.5 61
Relay arm and swingarm M14 × 1.5 1 80 8.0 58
Relay arm and connecting rod M14 × 1.5 1 80 8.0 58
Connecting rod and frame M14 × 1.5 1 80 8.0 58
Rear shock absorber and frame M10 × 1.25 1 56 5.6 40
Rear shock absorber and relay arm M10 × 1.25 1 53 5.3 38
Rear frame and frame (upper) M8 × 1.25 1 32 3.2 23
Rear frame and frame (lower) M8 × 1.25 2 29 2.9 21
Swingarm and brake hose holder M5 × 0.8 4 1 0.1 0.7
Swingarm and patch M4 × 0.7 4 2 0.2 1.4
Drive chain tensioner mounting (upper) M8 × 1.25 1 19 1.9 13
Drive chain tensioner mounting (lower) M8 × 1.25 1 20 2.0 14
Chain support and swingarm M6 × 1.0 3 7 0.7 5.1
Seal guard and swingarm M5 × 0.8 4 6 0.6 4.3
Fuel tank mounting M6 × 1.0 2 10 1.0 7.2
Fuel tank and fuel cock M6 × 1.0 2 7 0.7 5.1
Fuel tank and seat set bracket M6 × 1.0 1 7 0.7 5.1
Fuel tank and hooking screw (fitting band) M6 × 1.0 1 7 0.7 5.1
Fuel tank and fuel tank bracket M6 × 1.0 4 7 0.7 5.1
Seat mounting M8 × 1.25 2 23 2.3 17
Side cover mounting M6 × 1.0 2 7 0.7 5.1
Air scoop and fuel tank M6 × 1.0 6 4 0.4 2.9
Air scoop and radiator panel (lower) M6 × 1.0 2 4 0.4 2.9
Front fender mounting M6 × 1.0 4 7 0.7 5.1
Rear fender mounting (front) M6 × 1.0 2 7 0.7 5.1
Rear fender mounting (rear) M6 × 1.0 2 10 1.0 7.2
Number plate M6 × 1.0 1 7 0.7 5.1

2 - 21
SPEC

CABLE ROUTING DIAGRAM
EC240000
CABLE ROUTING DIAGRAM
1
Fuel tank breather hose
2
Hot starter cable
3
Radiator hose 4
4
Cylinder head breather hose
5
Radiator hose 1
6
Oil tank breather hose
7
Hose guide
8
Brake hose
9
“ENGINE STOP” button lead
0
Clamp
A
Sub wire harness
B
TPS (throttle position sen-
sor) lead
C
Neutral switch lead
D
Oil hose
E
Radiator breather hose
F
CDI magneto lead
G
Carburetor breather hose
H
Overflow hose
Å
Pass the fuel tank breather hose
between the handlebar and ten-
sion bar, then insert its end into
the hole of the number plate.
ı
Pass the hot starter cable
between the cylinder head
breather hose, oil tank breather
hose and ignition coil, then on
the outside of the left engine
bracket.
Ç
Pass the cylinder head breather
hose on the outside of the radia-
tor hose 1 and on the inside of the
radiator pipe (radiator hose 4).
Î
Fit the brake hose into the
guides on the protector.
‰
Fasten the “ENGINE STOP”
button lead and sub wire har-
ness to the frame with a plastic
locking tie and cut off the tie
end.
ÏFasten the sub wire harness
and hot starter cable to the
frame at the white tape for the
sub wire harness with a plastic
locking tie and cut off the tie
end.
ÌFasten the sub wire harness to
the frame with a plastic locking
tie and cut off the tie end.
C
9
0
A
0
0
0
0
0
B
C
D
0 0 E 0 F 0
1
2 8
7
6
5
4
3GHG9A
D
E
C
B
A
A
C
BB
Ç ÎÅ
ıØ
˜ ˆ
Ò
Ô ÈÌ Ó Ì Ï ‰ ‰
∏
*
*

2 - 25
SPECCABLE ROUTING DIAGRAM
1Throttle cable
2Fuel tank breather hose
3Clamp
4Clutch cable
5Hot starter cable
6“ENGINE STOP” button lead
7Brake hose
8Hose guideÅFasten the “ENGINE STOP” but-
ton lead to the handlebar with the
plastic band.
ıPass the brake hose in front of the
number plate.
ÇPass the hot starter cable, clutch
cable and throttle cables through
the cable guide.
*Decompression cable (supplied
for Europe and optional for other
destinations)
1
23
4
5
6
7
83
6 Å
Çı
40˚±10˚
A
A
*

3 - 2
INSP
ADJ

MAINTENANCE INTERVALS
SHIFT FORK, SHIFT CAM, GUIDE BAR
Inspect
●
Inspect wear
ROTOR NUT
Retighten
●

●

MUFFLER
Inspect and retighten
Clean
Replace
●

●

●

●
* Whichever comes first
CRANK
Inspect and clean
●

●

CARBURETOR
Inspect, adjust and clean
●

●
When using a high-pres-
sure washer, make sure
that water does not enter
the accelerator pump.
SPARK PLUG
Inspect and clean
Replace
●

●

●

DRIVE CHAIN
Lubricate, slack, alignment
Replace
●

●

●
Use chain lube
Chain slack: 40 ~ 50 mm
(1.6 ~ 2.0 in)
COOLING SYSTEM
Check coolant level and leakage
Check radiator cap operation
Replace coolant
Inspect hoses
●

●

●

●

●
Every two years
OUTSIDE NUTS AND BOLTS
Retighten
●

●
Refer to “STARTING
AND BREAK-IN” section
in the CHAPTER 1.
AIR FILTER
Clean and lubricate
Replace
●

●

●
Use foam air-filter oil or
equivalent oil
OIL FILTER
Replace
●

●

OIL STRAINER (frame)
Clean
●

FRAME
Clean and inspect
●

●

FUEL TANK, COCK
Clean and inspect
●

●

BRAKES
Adjust lever position and pedal height
Lubricate pivot point
Check brake disc surface
Check fluid level and leakage
Retighten brake disc bolts, caliper
bolts, master cylinder bolts and union
bolts
Replace pads
Replace brake fluid
●

●

●

●

●

●

●

●

●

●

●

●
Every one year
FRONT FORKS
Inspect and adjust
Replace oil
Replace oil seal
●

●

●

●

●
Suspension oil “01” ItemAfter
break-inEvery
race
Every
third
(or
500 km)Every
fifth
(or
1,000 km)
As re-
quiredRemarks


3

3 - 4
INSP
ADJ
PRE-OPERATION INSPECTION AND MAINTENANCE
EC320000
PRE-OPERATION INSPECTION AND MAINTENANCE
Before riding for break-in operation, practice or a race, make sure the machine is in good operating
condition.
Before using this machine, check the following points.
GENERAL INSPECTION AND MAINTENANCE
Item Routine Page
CoolantCheck that coolant is filled up to the radiator filler cap.
Check the cooling system for leakage.P.3-5 ~ 9
FuelCheck that a fresh gasoline is filled in the fuel tank. Check the
fuel line for leakage.P.1-17
Engine oilCheck that the oil level is correct. Check the crankcase and
frame oil line for leakage.P.3-13 ~ 17
Gear shifter and clutchCheck that gears can be shifted correctly in order and that the
clutch operates smoothly.P.3-9
Throttle grip/HousingCheck that the throttle grip operation and free play are correctly
adjusted. Lubricate the throttle grip and housing, if necessary.P.3-10
Brakes Check the play of front brake and effect of front and rear brake. P.3-24 ~ 30
ChainCheck chain slack and alignment. Check that the chain is lubri-
cated properly.P.3-31 ~ 33
WheelsCheck for excessive wear and tire pressure. Check for loose
spokes and have no excessive play.P.3-41 ~ 42
SteeringCheck that the handlebar can be turned smoothly and have no
excessive play.P.3-42 ~ 43
Front forks and rear shock
absorberCheck that they operate smoothly and there is no oil leakage. P.3-33 ~ 40
Cables (wires)Check that the clutch and throttle cables move smoothly. Check
that they are not caught when the handlebars are turned or
when the front forks travel up and down.—
Muffler Check that the muffler is tightly mounted and has no cracks.—
Sprocket Check that the driven sprocket tightening bolt is not loose. P.3-31
Lubrication Check for smooth operation. Lubricate if necessary. P.3-44
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P.1-22
Lead connectorsCheck that the CDI magneto, CDI unit, and ignition coil are con-
nected tightly.P.1-6
SettingsIs the machine set suitably for the condition of the racing course
and weather or by taking into account the results of test runs
before racing? Are inspection and maintenance completely
done?P.7-1 ~ 21

3 - 17
INSP
ADJ
PILOT SCREW ADJUSTMENT
12. Check:
Oil pressure
Checking steps:
Slightly loosen the oil gallery bolt 1.
Start the engine and keep it idling until oil
starts to seep from the oil gallery bolt. If no
oil comes out after one minute, turn the
engine off so it will not seize.
Check oil passages, oil filter and oil pump
for damage or leakage.
Start the engine after solving the prob-
lem(s) and recheck the oil pressure.
Tighten the oil gallery bolt to specification.
T R..
Oil gallery bolt:
10 Nm (1.0 m • kg, 7.2 ft • lb)
PILOT SCREW ADJUSTMENT
1. Adjust:
Pilot screw 1
Adjusting steps:
NOTE:
To optimize the fuel flow at a smaller throttle
opening, each machine’s pilot screw has
been individually set at the factory. Before
adjusting the pilot screw, turn it in fully and
count the number of turns. Record this num-
ber as the factory-set number of turns out.
Turn in the pilot screw until it is lightly
seated.
Turn out the pilot screw by the factory-set
number of turns.
Pilot screw:
2 turns out (example)

3 - 18
INSP
ADJIDLE SPEED ADJUSTMENT/
VALVE CLEARANCE ADJUSTMENT
EC35M021
IDLE SPEED ADJUSTMENT
1. Start the engine and thoroughly warm it
up.
2. Adjust:
Idle speed
Adjustment steps:
Adjust the pilot screw.
Refer to “PILOT SCREW ADJUSTMENT”
section.
Turn the throttle stop screw 1 until the
engine runs at the lowest possible speed.
To increase idle speed →
Turn the throttle stop screw 1 in a.
To decrease idle speed →
Turn the throttle stop screw 1 out b.
Engine idling speed:
1,900 ~ 2,100 r/min
VALVE CLEARANCE ADJUSTMENT
NOTE:
The valve clearance should be adjusted
when the engine is cool to the touch.
The piston must be at Top Dead Center
(T.D.C.) on compression stroke to check or
adjust the valve clearance.
1. Remove:
Seat
Fuel tank
Refer to “SEAT, FUEL TANK AND SIDE
COVERS” section in the CHAPTER 4.
2. Remove:
Carburetor
Refer to “CARBURETOR” section in
the CHAPTER 4.
Spark plug cap
Engine stay (upper)
Cylinder head cover
Refer to “CAMSHAFTS” section in the
CHAPTER 4.
3. Remove:
Timing plug 1
Straight plug 2
O-ring

3 - 43
INSP
ADJ
STEERING HEAD INSPECTION AND ADJUSTMENT
Tighten the ring nut 3 using ring nut
wrench 4.
NOTE:
Apply the lithium soap base grease on the
thread of the steering shaft.
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 handle crown 5, plain washer,
steering shaft nut 6, handlebar 7, han-
dlebar holder 8 and number plate 9.
NOTE:
The upper handlebar holder should be
installed with the punched mark a for-
ward.
Insert the end of fuel breather hose 0 into
the hole of the number plate.
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 upper holder:
28 Nm (2.8 m • kg, 20 ft • lb)
Pinch bolt (handle crown):
23 Nm (2.3 m • kg, 17 ft • lb)
Number plate:
7 Nm (0.7 m • kg, 5.1 ft • lb)