2015 YAMAHA YZ450F oil

FRONT FORK
4-40
5. Remove:
• Base valve “1”
(from the damper assembly)
TIP
Hold the damper assembly with the cap bolt
ring wrench “2” and use the cap bolt wrench “3”
to remove the base valve.
EAS1SL5169CHECKING THE FRONT FORK LEGS
1. Check:
• Inner tube surface “a”
Scratches  Repair or replace.
Use #1000 grit wet sandpaper.
Damaged oil lock piece  Replace.
• Inner tube bends
Out of specification  Replace.
Use the dial gauge “1”.
TIP
The bending value is shown by one half of the
dial gauge reading.
EWA13650
WARNING
Do not attempt to straighten a bent inner
tube as this may dangerously weaken it.2. Check:
• Outer tube
Scratches/wear/damage  Replace.
3. Measure:
• Fork spring free length “a”
Out of specification  Replace.
4. Check:
• Damper assembly “1”
Bend/damage  Replace.
• O-ring “2”
Wear/damage  Replace.
ECA1DX1010
NOTICE
• The front fork leg has a built-in damper ad-
justing rod and a very sophisticated inter-
nal construction, which are particularly
sensitive to foreign material.
• When disassembling and assembling the
front fork leg, do not allow any foreign ma-
terial to enter the front fork. Cap bolt wrench
90890-01500
YM-01500
Cap bolt ring wrench
90890-01501
YM-01501
Inner tube bending limit
0.2 mm (0.01 in)
1 23
Fork spring free length
497.0 mm (19.57 in)
Limit
492.0 mm (19.37 in)

FRONT FORK
4-41
5. Check:
• Base valve “1”
Wear/damage  Replace.
Contamination  Clean.
• O-rings “2”
Wear/damage  Replace.
• Base valve bushing “3”
Wear/damage  Replace.
• Spring “4”
Damage/fatigue  Replace the base valve.
• Air bleed screw “5”
Wear/damage  Replace.
6. Check:
• Contacting surface “a”
Wear/damage  Replace.
7. Check:
• Adjuster “1”
• O-rings “2”
Wear/damage  Replace.EAS1SL5170ASSEMBLING THE FRONT FORK LEGSEWA13660
WARNING
• Make sure the oil levels in both front fork
legs are equal.
• Uneven oil levels can result in poor han-
dling and a loss of stability.
TIP
• When assembling the front fork leg, be sure to
replace the following parts:
• Inner tube bushing
• Outer tube bushing
• Oil seals
• Copper washers
• Before assembling the front fork leg, make
sure that all of the components are clean.
1. Stretch the damper assembly fully.
2. Fill:
• Damper assembly
ECA14210
NOTICE
• Be sure to use the recommended oil. Other
oils may have an adverse effect on front
fork performance.
• When disassembling and assembling the
front fork leg, take care not to allow any
foreign material to enter the front fork.
3. After filling, pump the damper assembly “1”
slowly up and down (about 200 mm (7.9 in)
stroke) several times to bleed the damper
assembly of air.
TIP
Avoid excessive full stroke. A stroke of 200 mm
(7.9 in) or more will cause air to enter. In this
case, repeat the steps 1 to 3.
21
New
New
New
2
21 543
a
New
Recommended oil
Suspension oil S1
Standard oil amount
204 cm
3 (6.90 US oz, 7.20
Imp.oz)
New
1
2

FRONT FORK
4-42
4. Measure:
• Oil level (left and right) “a”
Out of specification  Regulate.
5. Tighten:
• Locknut “1”
TIP
Fully finger tighten the locknut onto the damper
assembly.6. Loosen:
• Compression damping force adjuster “1”
TIP
• Before loosening the damping force adjuster,
record the setting position.
• Unless the damping force adjuster is fully
loosened, correct damping characteristic can-
not be obtained after installation.
7. Install:
• Base valve “1”
(to the damper assembly “2”)
TIP
First bring the damper rod pressure to a maxi-
mum. Then install the base valve while releas-
ing the damper rod pressure.
8. Check:
• Damper assembly
Not fully stretched  Repeat the steps 1 to
7.
9. Tighten:
• Base valve “1”
TIP
Hold the damper assembly with the cap bolt
ring wrench “2” and use the cap bolt wrench “3”
to tighten the base valve. Standard oil level
145–148 mm (5.71–5.83 in)
From top of fully stretched
damper assembly.
1
a
Base valve
28 Nm (2.8 m·kgf, 20 ft·lbf)
1
1
2
T R..

FRONT FORK
4-43
10.After filling, pump the damper assembly “1”
slowly up and down more than 10 times to
distribute the fork oil.
11.While protecting the damper assembly “1”
with a cloth and compressing fully, allow ex-
cessive oil to overflow on the base valve
side.
ECA32D1010
NOTICE
Take care not to damage the damper assem-
bly.
12.Allow the overflowing oil to escape at the
hole “a” in the damper assembly.
TIP
The overflow measures about 8 cm3 (0.27 US
oz, 0.28 lmp oz).13.Check:
• Damper assembly smooth movement
Tightness/binding/rough spots  Repeat
the steps 1 to 12.
14.Install:
• Dust seal “1”
• Oil seal clip “2”
• Oil seals “3”
• Washer “4”
• Outer tube bushing “5”
(to the inner tube “6”)
ECA32D1010
NOTICE
Make sure that the numbered side of the oil
seal faces bottom side.
TIP
• Apply the lithium soap base grease on the
dust seal lip and oil seal lip.
• Apply the fork oil on the inner tube.
• When installing the oil seal, use vinyl seat “a”
with fork oil applied to protect the oil seal lip. Cap bolt wrench
90890-01500
YM-01500
Cap bolt ring wrench
90890-01501
YM-01501
1 23
1
1
a
New
New
New
LS

FRONT FORK
4-44
15.Install:
• Inner tube bushing “1”
TIP
Install the inner tube bushing onto the slot on
inner tube.
16.Install:
• Outer tube “1”
(to the inner tube “2”)
17.Install:
• Inner tube bushing “1”
• Washer “2”
(to the outer tube)
TIP
Press the inner tube bushing into the outer tube
with fork seal driver “3”.18.Install:
• Oil seals “1”
TIP
Using a fork seal driver “2,” press the oil seal in
until the stopper ring groove fully appears.
19.Install:
• Oil seal clip “1”
TIP
Fit the oil seal clip correctly in the groove in the
outer tube.
Fork seal driver
90890-01502
YM-A0948
New
Fork seal driver
90890-01502
YM-A0948
New

FRONT FORK
4-47
30.Fill:
• Front fork leg
ECA14210
NOTICE
• Be sure to use the recommended oil. Other
oils may have an adverse effect on front
fork performance.
• When disassembling and assembling the
front fork leg, do not allow any foreign ma-
terial to enter the front fork.
31.Install:
• Damper assembly “1”
(to the outer tube)
TIP
Temporarily tighten the damper assembly.
32.Install:
• Protector guide “1”
EAS1SL5171INSTALLING THE FRONT FORK LEGS
1. Install:
• Front fork “1”
TIP
• Temporarily tighten the pinch bolts (lower
bracket).
• Do not tighten the pinch bolts (upper bracket)
yet.
2. Tighten:
• Damper assembly “1”
TIP
Use the cap bolt ring wrench “2” to tighten the
damper assembly. Recommended oil
Suspension oil S1
Standard oil amount
315 cm
3 (10.65 US oz, 11.11 lmp
oz) (USA) (CAN)
355 cm
3 (12.00 US oz, 12.52 lmp
oz) (EUR) (JPN) (AUS) (NZL)
(ZAF)
Extent of adjustment
300–365 cm
3 (10.14–12.34 US
oz, 10.58–12.87 lmp oz)
Damper assembly
30 Nm (3.0 m·kgf, 22 ft·lbf)
Cap bolt ring wrench
90890-01501
YM-01501
1
T R..
2
1

REAR SHOCK ABSORBER ASSEMBLY
4-55
Disassembling the relay arm
Order Part name Q’ty Remarks
1 Relay arm 1
2 Connecting arm 1
3Collars 3
4Oil seals 6
5Washers 8
6 Bearing 6
For assembly, reverse the disassemble pro-
cedure.
5
3
5
6
165
4
5
5
4
5
6
6
5
4
3
2
4
6
6
3
4
4
T.R.80 Nm (8.0 mlbf) kgf, 58 ft
M
M
M
M
M MM

REAR SHOCK ABSORBER ASSEMBLY
4-57
2. Remove:
• Upper bearing “1”
TIP
Remove the bearing by pressing its outer race.
3. Remove:
• Lower bearing “1”
TIP
Remove the bearing by pressing its outer race.
EAS1SL5181CHECKING THE REAR SHOCK ABSORBER
ASSEMBLY
1. Check:
• Rear shock absorber rod
Bends/damage  Replace the rear shock
absorber assembly.
• Rear shock absorber
Gas leaks/oil leaks  Replace the rear
shock absorber assembly.
•Spring
Damage/wear  Replace.
• Spring guide
Damage/wear  Replace.
• Bearing
Damage/wear  Replace.
•Bolts
Bends/damage/wear  Replace.
EAS1SL5182
CHECKING THE CONNECTING ARM AND
RELAY ARM
1. Check:
• Connecting arm
• Relay arm
Damage/wear  Replace.
2. Check:
• Bearing
• Spacers
Damage/pitting/scratches  Replace the
bearings and spacers as a set.
3. Check:
• Oil seals
Damage/pitting  Replace.
EAS1SL5183INSTALLING THE RELAY ARM
1. Lubricate:
• Oil seals
• Bearing
• Spacers
• Washers
•Collars
2. Install:
• Bearing “1”
• Washer “2”
• Oil seals “3”
(to relay arm “4”)
3. Install:
• Bearing “1”
• Oil seals “2”
(to connecting arm “3”)
1
Recommended lubricant
Molybdenum disulfide grease
Installed depth “a”
0 mm (0 in)
Installed depth “a”
0 mm (0 in)
New
3 3
43
2 2
22
a
1
11
New