2015 YAMAHA YZ450F oil

CHASSIS
3-28
EAS1SL5100CHECKING THE FRONT FORK LEGS
1. Stand the vehicle upright on a level surface.
EWA13120
WARNING
Securely support the vehicle so that there is
no danger of it falling over.
2. Check:
• Inner tube
Damage/scratches  Replace.
• Front fork leg (s)
Oil leaks between inner tube and outer tube
 Replace the oil seal.
3. Hold the vehicle upright and apply the front
brake.
4. Check:
• Front fork operation
Push down hard on the handlebar several
times and check if the front fork rebounds
smoothly.
Unsmooth operation  Correct or replace.
Refer to “FRONT FORK” on page 4-37.
EAS1SL5101CHECKING THE FRONT FORK PROTEC-
TOR GUIDE
1. Check:
• Protector guide “1”
Out of specification  Replace.
TIP
The protector guide reaches the limit of its use
when it is worn down to the same height “a” as
of the outer tube circumference.
EAS1SL5102
CLEANING THE FRONT FORK OIL SEAL
AND DUST SEAL
1. Remove:
•Protector
• Dust seal “1”
ECA?
NOTICE
Be careful not to damage the dust seal and
the inner tube by a driver.
2. Clean:
• Dust seal “a”
• Oil seal “b”
TIP
• Clean the dust seal and oil seal after every
run.
• Apply lithium-soap-based grease on the inner
tube.
EAS1SL5103AIR BLEEDING FROM FRONT FORK
TIP
If the front fork initial movement feels stiff dur-
ing a run, relieve the front fork internal pres-
sure.
1. Use a suitable stand to raise the front wheel
off the ground.
EWA@
WARNING
Securely support the vehicle so that there is
no danger of it falling over.
2. Remove the air bleed screw “1” and release
the internal pressure from the front fork.
1
a
1
LS
a
b

CHASSIS
3-30
EAS1SL5105CHECKING THE SWINGARM OPERATION
1. Check:
• Swingarm smooth action
• Swingarm free play
Refer to “SWINGARM” on page 4-60.
EAS1SL5106CHECKING THE REAR SUSPENSION
1. Stand the vehicle upright on a level surface.
EWA@
WARNING
Securely support the vehicle so that there is
no danger of it falling over.
2. Check:
• Rear shock absorber assembly
Gas leaks/oil leaks  Replace the rear
shock absorber assembly.
Refer to “REAR SHOCK ABSORBER AS-
SEMBLY” on page 4-53.
3. Check:
• Rear shock absorber assembly smooth ac-
tion
• Rear suspension link smooth action
Sit astride the seat and shake your body up
and down several times to check whether
the rear shock absorber assembly operates
smoothly.
Unsmooth operation  Correct or replace.
Refer to “REAR SHOCK ABSORBER AS-
SEMBLY” on page 4-53.
EAS1SL5107ADJUSTING THE REAR SHOCK ABSORB-
ER ASSEMBLY
Use a suitable stand to raise the rear wheel off
the ground.
EWA13120
WARNING
Securely support the vehicle so that there is
no danger of it falling over.
Spring preload
ECA@
NOTICE
Do not turn the adjuster forcibly beyond its
adjusting range.1. Remove:
• Rear frame
Refer to “REAR SHOCK ABSORBER AS-
SEMBLY” on page 4-53.
2. Adjust:
• Spring preload
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Loosen the locknut “1”.
b. Loosen the adjuster “2” until there is some
clearance between the spring and the ad-
juster.
c. Measure the spring free length “a”.
d. Turn the adjuster in the direction of “b” or “c”
to make an adjustment.
TIP
• Be sure to remove all dirt and mud from
around the locknut and adjusting ring before
adjustment.
• The length of the spring (installed) changes
1.5 mm (0.06 in) per turn of the adjusting ring.
Direction “b”
Spring preload is increased (suspen-
sion is harder).
Direction “c”
Spring preload is decreased (suspen-
sion is softer).
Spring installed length “d”
Minimum
Position in which the spring is
turned in 1.5 mm (0.06 in) from
its free length.
STD
Position in which the spring is
turned in 10 mm (0.39 in) from its
free length.
Maximum
Position in which the spring is
turned in 18 mm (0.71 in) from its
free length.

FRONT WHEEL
4-3
EAS1SL5123
FRONT WHEEL
Removing the front wheel
Order Part name Q’ty Remarks
Use a suitable stand to raise the front wheel
off the ground.
1 Front wheel axle pinch bolt 4 Loosen.
2 Front wheel axle nut 1
3 Front wheel axle 1
4 Front wheel 1
5Collars 2
6Oil seals 2
7 Bearing 2
8 Brake disc 1
For installation, reverse the removal proce-
dure.
12 Nm (1.2 mkgf, 8.7 ftIbf)T.R
.
New
New
LT
LS
LS
LS
5
76
5 6 7
(6)
8
12
1 3
21 Nm (2.1 mkgf, 15 ftIbf)T.R.
21 Nm (2.1 mkgf, 15 ftIbf)T.R.
4
115 Nm (11.5 mkgf, 83 ftlbf)T.R.

FRONT WHEEL
4-4
EAS1SL5124REMOVING THE FRONT WHEEL
1. Use a suitable stand to raise the front wheel
off the ground.
EWA13120
WARNING
Securely support the vehicle so that there is
no danger of it falling over.
2. Remove:
• Front wheel
EAS1SL5125CHECKING THE FRONT WHEEL
1. Check:
• Front wheel axle
Roll the front wheel axle on a flat surface.
Bends  Replace.
EWA13460
WARNING
Do not attempt to straighten a bent wheel
axle.
2. Check:
•Tire (s)
• Front wheel
Damage/wear  Replace.
Refer to “CHECKING THE TIRES” on page
3-32 and “CHECKING THE WHEELS” on
page 3-33.
3. Check:
• Spokes
Bend/damage  Replace.
Loose  Tighten.
Tap the spokes with a screwdriver.
TIP
A tight spoke will emit a clear, ringing tone; a
loose spoke will sound flat.
4. Tighten:
• Spokes
Refer to “CHECKING AND TIGHTENING
THE SPOKES” on page 3-32.
TIP
After tightening the spokes, measure the wheel
runout.
5. Measure:
• Wheel radial runout “a”
• Wheel lateral runout “b”
Out of specification  Repair/replace.
6. Check:
•Collars
Damage/wear  Replace.
7. Check:
• Bearing
Front wheel turns roughly or is loose  Re-
place the wheel bearings.
• Oil seals
Damage/wear  Replace.
Spokes
2.5 Nm (0.25 m·kgf, 1.8 ft·lbf)
Radial wheel runout limit
2.0 mm (0.08 in)
Lateral wheel runout limit
2.0 mm (0.08 in)
T R..
ab

FRONT WHEEL
4-5
EAS1SL5126DISASSEMBLING THE FRONT WHEEL
1. Remove:
• Oil seals
• Bearing
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Clean the outside of the front wheel hub.
b. Remove the oil seals “1” with a flat-head
screwdriver.
TIP
To prevent damaging the wheel, place a rag “2”
between the screwdriver and the wheel sur-
face.
c. Remove the bearings with a bearing puller.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS1SL5127ASSEMBLING THE FRONT WHEEL
1. Install:
• Bearing (left side) “1”
• Spacer “2”
• Bearing (right side) “3”
• Oil seals “4”
TIP
• Apply the lithium soap base grease to the
bearing and the oil seal lip when installing.
• Left side of bearing shall be installed first.
• Install the oil seal with its manufacture’s
marks or numbers facing outward.
ECA1DX1005
NOTICE
Install the bearing by pressing its outer race
parallel.
TIP
Use a socket “1” that matches the diameter of
the bearing outer race and that of the oil seal.
2. Install:
• Brake disc “1”
• Brake disc bolt “2”
TIP
Tighten the bolts in stages and in a crisscross
pattern.
12
New
Brake disc bolt
12 Nm (1.2 m·kgf, 8.7 ft·lbf)
LOCTITE®
4
3
2
1
4
New
New
1
T R..

FRONT WHEEL
4-6
3. Install:
• Collar “1”
TIP
Apply the lithium soap base grease on the oil
seal lip.
EAS1SL5128INSTALLING THE FRONT WHEEL
1. Install:
• Front wheel
TIP
Install the brake disc “1” between the brake
pads “2” correctly.
2. Install:
• Front wheel axle “1”
TIP
Apply the lithium soap base grease to the front
wheel axle.3. Tighten:
• Front wheel axle nut “1”
ECA14140
NOTICE
Before tightening the front wheel axle nut,
push down hard on the handlebar(s) several
times and check if the front fork rebounds
smoothly.
4. Tighten:
• Front wheel axle pinch bolt “1”
1
LS
Front wheel axle nut
115 Nm (11.5 m·kgf, 83 ft·lbf)
Front wheel axle pinch bolt
21 Nm (2.1 m·kgf, 15 ft·lbf)
T R..
1
T R..
1 1

REAR WHEEL
4-7
EAS1SL5129
REAR WHEEL
Removing the rear wheel
Order Part name Q’ty Remarks
Use a suitable stand to raise the rear wheel
off the ground.
1 Nut (rear wheel axle) 1
2 Rear wheel axle 1
3 Drive chain puller 2
4 Rear wheel 1
5Collars 2
6 Rear wheel sprocket 1
7Oil seals 2
8 Circlip 1
9 Bearing 3
10 Brake disc 1
For installation, reverse the removal proce-
dure.
(6)
21 Nm (2.1 m•kgf, 15 ft•Ibf)T.R.
2 5
7 9
LS
LS(6)
46
1
(6) 3
LS
8
9 10
7 5
LT
14 Nm (1.4 m•kgf, 10 ft•Ibf)T.R.
3
21 Nm (2.1 m•kgf, 15 ft•Ibf)T.R.
42 Nm (4.2 m•kgf, 30 ft•Ibf)T.R.
135 Nm (13.5 m•kgf, 98 ft•lbf)T.R.

REAR WHEEL
4-8
EAS1SL5130REMOVING THE REAR WHEEL
1. Use a suitable stand to raise the rear wheel
off the ground.
EWA13120
WARNING
Securely support the vehicle so that there is
no danger of it falling over.
2. Remove:
• Rear wheel axle nut “1”
3. Loosen:
• Locknut “2”
4. Tighten:
• Adjusting bolt “3”
5. Remove:
• Rear wheel axle
• Rear wheel
TIP
• Push the rear wheel forward and remove the
drive chain from the rear wheel sprocket.
• Do not depress the brake pedal with the rear
wheel removed.
EAS1SL5131CHECKING THE REAR WHEEL
1. Check:
• Rear wheel axle
• Rear wheel
• Bearing
• Oil seals
Refer to “CHECKING THE FRONT WHEEL”
on page 4-4.
2. Check:
•Tire (s)
• Rear wheel
Damage/wear  Replace.
Refer to “CHECKING THE TIRES” on page
3-32 and “CHECKING THE WHEELS” on
page 3-33.
3. Check:
• Spokes
Refer to “CHECKING THE FRONT WHEEL”
on page 4-4.4. Measure:
• Radial wheel runout
• Lateral wheel runout
Refer to “CHECKING THE FRONT WHEEL”
on page 4-4.
EAS1SL5132DISASSEMBLING THE REAR WHEEL
1. Remove:
• Oil seals
• Bearing
Refer to “DISASSEMBLING THE FRONT
WHEEL” on page 4-5.
EAS1SL5133CHECKING AND REPLACING THE REAR
WHEEL SPROCKET
1. Check:
• Rear wheel sprocket
More than 1/4 tooth wear “a”  Replace the
rear wheel sprocket and the drive sprocket
as a set.
Bent tooth  Replace the rear wheel
sprocket and the drive sprocket as a set.
2. Replace:
• Rear wheel sprocket
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Remove the self-locking nuts and the rear
wheel sprocket.
b. Clean the rear wheel drive hub with a clean
cloth, especially the surfaces that contact
the sprocket.
c. Install the new rear wheel sprocket.
3
12
Radial wheel runout limit
2.0 mm (0.08 in)
Lateral wheel runout limit
2.0 mm (0.08 in)
b. Correct
1. Drive chain roller
2. Rear wheel sprocket
Rear wheel sprocket self-locking
nut
42 Nm (4.2 m·kgf, 30 ft·lbf)
T R..