YAMAHA YFZ450R 2021 Service Manual

5-15
5
Slow compression damping force
Turn the slow compression damping force adjust-
ing screw in direction (a) to increase the slow com-
pression damping force. Turn in direction (b) to
decrease the slow compression damping force.
WARNING
EWB00411These shock absorber assemblies contain
highly pressurized nitrogen gas. Read and un-
derstand the following information before han-
dling the shock absorber assemblies.

Do not tamper with or attempt to open the
cylinder assemblies.
 Do not subject the shock absorber assem-
blies to an open flame or other high heat
source. This may cause the unit to explode
due to excessive gas pressure.
 Do not deform or damage the cylinders in
any way. Cylinder damage will result in poor
damping performance.
 Do not dispose of a damaged or worn out
shock absorber assembly yourself. Take the
shock absorber assembly to a Yamaha deal-
er for any service. EBU30147Rear shock absorberThe shock absorber spring preload, rebound
damping force, and compression damping force
(fast and slow compression damping) can be ad-
justed.
1. Slow compression damping force adjusting screwSlow compression damping force settings:
Minimum (soft):20 click(s) in direction (b)
Standard: 7 click(s) in direction (b)
Maximum (hard): 1 click(s) in direction (b)
(a)
(b)
1
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5-16
5
WARNING
EWB02681Suspension components become hot during
operation. Never touch the compression
damping force adjusting bolt and screw, the
rebound damping force adjusting screw or the
oil reservoir with your bare hand or skin until
the suspension components have cooled. Notes on adjusting the suspension
A special wrench can be obtained at a Yamaha
dealer to make the spring preload adjustment.
 When adjusting the damping force settings, turn
the adjuster in direction (a) until it stops, and
then count the turns or clicks in direction (b).
 Although a damping force adjuster may turn or
click beyond the stated minimum settings, such
adjustments are ineffective and may damage
the suspension.NOTICEECB00091Never turn an adjusting mechanism beyond
the minimum and maximum settings.
Spring preload
1. Elevate the vehicle and place a suitable stand under the frame.
2. Remove the cowling. (See page 9-10.)
3. Remove the clip from the hose holder, re- move the bolt, and then move the blow-by
gas chamber away from the vehicle.
4. Loosen the clamp screw at the air filter case side.1. Hose holder
2. Clip
3. Bolt
4. Blow-by gas chamber
2 3
4
1
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5-17
5
5. Remove the air filter case holding plate by re- moving the bolts and collars. 6. Remove the bolts, and then remove the air fil-
ter case by disconnecting it from the air in-
take duct.
1. Clamp screw
1
1. Bolt
2. Collar
3. Air filter case holding plate
1
1
2
3
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5-18
57. Disconnect the coupler. 8. Loosen the clamp screw at the throttle body
side, and then disconnect the air intake duct
from the throttle body.
9. Loosen the locknut.
10. Turn the spring preload adjusting nut in direc- tion (a) to increase the spring preload and
thereby harden the suspension. Turn in direc-
tion (b) to decrease the spring preload and
thereby soften the suspension.
1. Air filter case
2. Bolt
1. Coupler
12
2
1
1. Clamp screw
2. Air intake duct
1
2
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5-19
5
TIPThe spring preload setting is determined by
measuring distance A, shown in the illustration.
 The shorter distance A is, the greater the spring
preload. The longer distance A is, the lesser the
spring preload.
 Each complete turn of the adjusting nut chang-
es distance A by 1.5 mm (0.06 in).
11. Tighten the locknut to the specified torque.
NOTICE: Always tighten the locknut
against the adjusting nut, and then tighten
it to the specified torque.
[ECB00082]
1. Locknut
2. Spring preload adjusting nut
3. Special wrench
2 13
(a)
(b)
Spring preload setting: Minimum (soft):Distance A = 286.5 mm (11.28 in)
Standard: Distance A = 278.0 mm (10.94 in)
Maximum (hard): Distance A = 266.5 mm (10.49 in)1. Distance A
1
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5-20
512. Connect the air intake duct to the throttle
body, and then tighten the clamp screw at the
throttle body side. NOTICE: Make sure that
the air intake duct is properly connected to
the throttle body, and that the clamp
screw is tightened securely.
[ECB00962]
13. Connect the coupler.
14. Connect the air filter case to the air intake duct, place the air filter case in the original po-
sition, and then tighten the clamp screw at
the air filter case side. NOTICE: Make sure
that the air intake duct is properly con-
nected to the air filter case, and that the
clamp screw is tightened securely.
[ECB00972]
15. Install the air filter case bolts, and then tighten them to the specified torque. 16. Install the air filter case holding plate by in-
stalling the bolts and collars, and then tighten
the bolts to the specified torque.
17. Install the blow-by gas chamber by installing the bolt, tighten the bolt to the specified
torque, and then install the clip to the hose
holder.
18. Install the cowling.
Rebound damping force
Turn the rebound damping force adjusting screw
in direction (a) to increase the rebound damping
force. Turn in direction (b) to decrease the re-
bound damping force.
Tightening torque:
Locknut:30 N·m (3.0 kgf·m, 22 lb·ft)
Tightening torque: Air filter case bolt:7 N·m (0.7 kgf·m, 5.2 lb·ft)
Tightening torque:Air filter case holding plate bolt:7 N·m (0.7 kgf·m, 5.2 lb·ft)
Tightening torque: Blow-by gas chamber bolt:7 N·m (0.7 kgf·m, 5.2 lb·ft)
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5-21
5
Compression damping force
Remove the seat to make this adjustment. (See
page 5-10.) If the adjustment is difficult, it may be
necessary to remove panels A and C. (See page
9-10.) Fast compression damping force
Turn the fast compression damping force adjust-
ing bolt in direction (a) to increase the fast com-
pression damping force. Turn in direction (b) to
decrease the fast compression damping force.
1. Rebound damping force adjusting screwRebound damping force settings:
Minimum (soft):30 click(s) in direction (b)
Standard: 15 click(s) in direction (b)
Maximum (hard): 1 click(s) in direction (b)
1
(a)
(b)
1. Fast compression damping force adjusting bolt
(a)
(b)
1
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5-22
5Slow compression damping force
Turn the slow compression damping force adjust-
ing screw in direction (a) to increase the slow com-
pression damping force. Turn in direction (b) to
decrease the slow compression damping force.
WARNING
EWB00431This shock absorber assembly contains highly
pressurized nitrogen gas. Read and under-
stand the following information before han-
dling the shock absorber assembly.
Fast compression damping force settings:
Minimum (soft):2 turn(s) out from the fully turned in posi-
tion
Standard: 1.25 turn(s) out from the fully turned in
position
Maximum (hard): Adjusting bolt fully turned in1. Slow compression damping force adjusting screwSlow compression damping force settings:Minimum (soft):20 click(s) in direction (b)
Standard: 8 click(s) in direction (b)
Maximum (hard): 1 click(s) in direction (b)
(a)
(b)
1
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5-23
5

Do not tamper with or attempt to open the
cylinder assembly.
 Do not subject the shock absorber assembly
to an open flame or other high heat source.
This may cause the unit to explode due to ex-
cessive gas pressure.
 Do not deform or damage the cylinder in any
way. Cylinder damage will result in poor
damping performance.
 Do not dispose of a damaged or worn out
shock absorber assembly yourself. Take the
shock absorber assembly to a Yamaha deal-
er for any service.

EBU29404Handlebar positionThe handlebar can be adjusted to one of four po-
sitions to suit your preference. Have a Yamaha
dealer adjust the position of the handlebar.1. Handlebar
1
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6-1
6
EBU19203
PRE-OPERATION CHECKS
EBU19227Inspect your vehicle each time you use it to make sure the vehicle is in safe operating condition. Always
follow the inspection and maintenance procedures and schedules described in the Owner’s Manual.
WARNING
EWB00482Failure to inspect or maintain the vehicle properly increases the possibility of an accident or equip-
ment damage. Do not operate the vehicle if you find any problem. If a problem cannot be corrected
by the procedures provided in this manual, have the vehicle inspected by a Yamaha dealer. Before using this vehicle, check the following points:
ITEMROUTINE PAGE
Fuel • Check fuel level in fuel tank,
and add recommended fuel if neces-
sary.
• Check fuel line for leakage. Correct if necessary. 5-9, 6-4
Engine oil • Check oil level in engine oil
tank, and add recommended oil to
specified level if necessary.
• Check ATV for oil leakage. Correct if necessary. 6-4, 9-14
Coolant • Check coolant level in reservoir, and add recommended coolant to
specified level if necessary.
• Check cooling system for leakage. Correct if necessary. 6-4, 9-20
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