Yamaha YZ450F 2021, Owner'S Service Manual

Page: 356 / 368

CHASSIS
10-3
TIP
Generally a stiff spring gives a stiff riding feeling.
Rebound damping tends to become weaker, re-
sulting in lack of a sense of contact with the road
surface or in a vibrating handlebar.
EAM30174
FRONT FORK SETTING PARTS
•
Front fork spring “1”
TIP
The I.D. mark (slits) “a” is proved on the end of
the spring.
EAM30175
REAR SUSPENSION SETTING
The rear shock absorber setting should be made
depending on the rider’s feeling of an actual run
and the circuit conditions.
The rear suspension setting includes the follow-
ing two factors:
1. Setting of spring preload
•
Change the set length of the spring.
• Change the spring.
2. Setting of damping force
• Change the rebound damping force.
•
Change the compression damping force.
EAM30176
CHOOSING SET LENGTH
1. Place a stand or a block under the engine to
put the rear wheel above the floor, and mea-
sure the length “a” between the rear wheel
axle center and the rear fender holding bolt.
2. Remove the stand or block from the engine
and, with a rider astride the seat, measure the
sunken length “b” between the rear wheel
axle center and the rear fender holding bolt.
3. Loosen the locknut “1” and make adjustment
by turning the adjuster “2” to achieve the
standard figure from the subtraction of the
length “b” from the length “a”.
TIP
•
If the machine is new and after it is broken in,
the same set length of the spring may change
because of the initial fatigue, etc. of the spring.
Therefore, be sure to make reevaluation.
STD Spring rate
N/mm
5.0
Type
Spring
rate
N/mm
Part number
I.D.
mark
(slits)
SOFT 4.5 BR9-23141-20 I-II
4.6 BR9-23141-30 I-III
4.7 BR9-23141-40 I-IIII
4.8 BR9-23141-50 I-IIIII
4.9 BR9-23141-60 II-II
5.0 BR9-23141-70 II-III
STIFF 5.1 BR9-23141-80 II-IIII
a
1
Standard figure
90–100 mm (3.5–3.9 in)
a
b