2004 YAMAHA YZ450F forks

1 - 19
GEN
INFO
CLEANING AND STORAGE
EC1B0000
CLEANING AND STORAGE
EC1B1000
CLEANING
Frequent cleaning of your machine will
enhance its appearance, maintain good overall
performance, and extend the life of many com-
ponents.
1. Before washing the machine, block off
the end of the exhaust pipe to prevent
water from entering. A plastic bag
secured with a rubber band may be used
for this purpose.
2. If the engine is excessively greasy, apply
some degreaser to it with a paint brush.
Do not apply degreaser to the chain,
sprockets, or wheel axles.
3. Rinse the dirt and degreaser off with a
garden hose; use only enough pressure
to do the job.
CAUTION:
Excessive hose pressure may cause water
seepage and contamination of wheel bear-
ings, front forks, brakes and transmission
seals. Many expensive repair bills have
resulted from improper high pressure
detergent applications such as those avail-
able in coin-operated car washers.
4. After the majority of the dirt has been
hosed off, wash all surfaces with warm
water and a mild detergent. Use an old
toothbrush to clean hard-to-reach places.
5. Rinse the machine off immediately with
clean water, and dry all surfaces with a
soft towel or cloth.
6. Immediately after washing, remove
excess water from the chain with a paper
towel and lubricate the chain to prevent
rust.
7. Clean the seat with a vinyl upholstery
cleaner to keep the cover pliable and
glossy.

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
● ●
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.1-13
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.1-18
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 ~ 23

3 - 42
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 number plate.
Remove the handlebar and handle crown.
Loosen the ring nut 1 using the ring nut
wrench 2.
Ring nut wrench:
YU-33975/90890-01403

4 - 95
ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
EC4H3000
REMOVAL POINTS
Shift fork, shaft cam and transmission
1. Remove:
Shift forks
Shift cam
Main axle
Drive axle
NOTE:
Tap lightly on the transmission drive axle and
shift cam with a soft hammer to remove.
Remove assembly carefully. Note the posi-
tion of each part. Pay particular attention to
the location and direction of shift forks.
EC4H4000
INSPECTION
EC4H4200
Gears
1. Inspect:
Matching dog a
Gear teeth b
Shift fork groove c
Wear/damage → Replace.
2. Inspect:
O-ring 1
Damage → Replace.
3. Check:
Gears movement
Unsmooth movement → Repair or
replace.
EC4H4600
Bearing
1. Inspect:
Bearing 1
Rotate inner race with a finger.
Rough spot/seizure → Replace.

5 - 28
CHASFRONT FORK
EC556000
HANDLING NOTE
NOTE:
The front fork requires careful attention. So it is
recommended that the front fork be main-
tained at the dealers.
CAUTION:
To prevent an accidental explosion of air,
the following instructions should be
observed:
The front fork with a built-in piston rod
has a very sophisticated internal con-
struction and is particularly sensitive to
foreign material.
Use enough care not to allow any foreign
material to come in when the oil is
replaced or when the front fork is disas-
sembled and reassembled.
Before removing the cap bolts or front
forks, be sure to extract the air from the
air chamber completely.
EC553000
REMOVAL POINTS
EC553150
Cap bolt
1. Remove:
Cap bolt 1
From the outer tube.
NOTE:
Before removing the front fork from the
machine, loosen the cap bolt.
2. Remove:
Cap bolt 1
NOTE:
Hold the locknut 2 and remove the cap bolt.

5 - 35
CHASFRONT FORK
19. Wait ten minutes until the air bubbles
have been removed from the front fork,
and the oil has dispense evenly in system
before setting recommended oil level.
NOTE:
Fill with the fork oil up to the top end of the
outer tube, or the fork oil will not spread over to
every part of the front forks, thus making it
impossible to obtain the correct level.
Be sure to fill with the fork oil up to the top of
the outer tube and bleed the front forks.
20. Measure:
Oil level (left and right) a
Out of specification → Adjust.
* For EUROPE
NOTE:
Be sure to install the spring guide 2 when
checking the oil level.
WARNING
Never fail to make the oil level adjustment
between the maximum and minimum level
and always adjust each front fork to the
same setting. Uneven adjustment can
cause poor handling and loss of stability.
Standard oil level:
125 mm (4.92 in)
*120 mm (4.72 in)
Extent of adjustment:
105 ~ 135 mm (4.13 ~ 5.31 in)
From top of outer tube with
inner tube and damper rod 1
fully compressed without
spring.