Yamaha YZ450FX 2019, Owner'S Service Manual

Page: 118 / 388

CHASSIS
3-30
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EAM30240
CHECKING THE SWINGARM OPERATION
1. Check:
•
Swingarm smooth action
• Swingarm free play
Refer to “SWINGARM” on page 4-61.
EAM30241
CHECKING THE REAR SUSPENSION
1. Stand the vehicle upright on a level surface.
WARNING
EWA13120
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 4-55.
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 4-55.
EAM30242
ADJUSTING THE REAR SHOCK ABSORBER
ASSEMBLY
Use a maintenance stand to raise the rear wheel
off the ground.
WARNING
EWA13120
Securely support the vehicle so that there is
no danger of it falling over.
Spring preload
NOTICE
ECA24360
Do not turn the adjuster forcibly beyond its
adjusting range.
1. Remove:
• Rear frame
Refer to “REAR SHOCK ABSORBER AS-
SEMBLY” on page 4-55.
2. Adjust:
• Spring preload
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a. Loosen the locknut “1”.
b. Loosen the adjuster “2” until there is some
clearance between the spring and the adjust-
er.
c. Measure the spring free length “a”.
d. Turn the adjuster in the direction of “b” or “c”
to make an adjustment.
1
a a b b
Direction “b”
Spring preload is increased (suspen-
sion is harder).
Direction “c”
Spring preload is decreased (suspen-
sion is softer).
1 1
2 2
a