2014 YAMAHA YZ450F length

10
TUNING
CHASSIS........................................................................................................ 10-1
SELECTION OF THE SECONDARY REDUCTION 
RATIO (SPROCKET) .............................................................................. 10-1
DRIVE AND REAR WHEEL SPROCKETS SETTING PARTS ................ 10-1
TIRE PRESSURE..................................................................................... 10-2
FRONT FORK SETTING.......................................................................... 10-2
CHANGE IN AMOUNT AND CHARACTERISTICS OF FORK OIL.......... 10-2
SETTING OF SPRING AFTER REPLACEMENT .................................... 10-3
FRONT FORK SETTING PARTS............................................................. 10-3
REAR SUSPENSION SETTING .............................................................. 10-3
CHOOSING SET LENGTH ...................................................................... 10-3
SETTING OF SPRING AFTER REPLACEMENT .................................... 10-4
REAR SHOCK ABSORBER SETTING PARTS ....................................... 10-5
SUSPENSION SETTING (FRONT FORK)............................................... 10-6
SUSPENSION SETTING (REAR SHOCK ABSORBER) ......................... 10-7

CHASSIS
10-3
SETTING OF SPRING AFTER REPLACE-
MENT
As the front fork setting can be easily affected
by the rear suspension, take care so that the
front and the rear are balanced (in position etc.)
when setting the front fork.
1. Use of soft spring
• Change the rebound damping force.
Turn out one or two clicks.
• Change the compression damping force.
Turn in one or two clicks.
TIP
Generally a soft spring gives a soft riding feel-
ing. Rebound damping tends to become stron-
ger and the front fork may sink deeply over a
series of gaps.
2. Use of stiff spring
• Change the rebound damping force.
Turn in one or two clicks.
• Change the compression damping force.
Turn out one or two clicks.
TIP
Generally a stiff spring gives a stiff riding feel-
ing. Rebound damping tends to become weak-
er, resulting in lack of a sense of contact with
the road surface or in a vibrating handlebar.
EAS1SL1372FRONT FORK SETTING PARTS
• Front fork spring “1”
*Except for USA and CAN
TIP
The I.D. mark (slits) “a” is proved on the end of
the spring.
EAS1SL1373REAR SUSPENSION SETTING
The rear shock absorber setting should be
made depending on the rider's feeling of an ac
-
tual run and the circuit conditions.
The rear suspension setting includes the fol-
lowing 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.
EAS1SL1374CHOOSING 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.
Type
Spring
rate
N/mm
Part number
I.D.
Mark
(slits)
SOFT3.91SL-23141-20|-||
4.61SL-23141-30|-|||
STD*4.71SL-23141-10—
1SL-23141-40|-||||
4.81SL-23141-50|-|||||
STD4.91SL-23141-00—
1SL-23141-60||-||
STIFF5.01SL-23141-70||-|||
a
1

CHASSIS
10-4
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 hold
-
ing 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 reevalua
-
tion.
• If the standard figure cannot be achieved by
adjusting the adjuster and changing the set
length, replace the spring with an optional one
and make readjustment.
EAS1SL1375
SETTING OF SPRING AFTER REPLACE-
MENT
After replacement, be sure to adjust the spring
to the set length [sunken length 90–100 mm
(3.5–3.9 in)] and set it.
1. Use of soft spring
• Adjust to decrease rebound damping force
to compensate for less spring load. Run with
the rebound damping force adjuster one or
two clicks turned out, and readjust it to suit
your preference.
2. Use of stiff spring
• Adjust to increase rebound damping force to
compensate for greater spring load. Run
with the rebound damping force adjuster
one or two clicks turned in, and readjust it to
suit your preference.
TIP
Adjusting the rebound damping force will be fol-
lowed more or less by a change in the com-
pression damping force. For correction, adjust
to decrease compression damping force.
EWA1DX4002
WARNING
When using a rear shock absorber other
than currently installed, use the one whose
overall length “a” does not exceed the stan
-
dard as it may result in faulty performance.
Never use one whose overall length is
greater than standard.
EAS1SL1376
Standard figure
90–100 mm (3.5–3.9 in)
Length “a” of standard shock
458.5 mm (18.05 in)

CHASSIS
10-5
REAR SHOCK ABSORBER SETTING
PARTS
• Rear shock spring “1”
*Except for USA and CAN
TIP
• The I.D. mark “a” is marked at the end of the
spring.
• Spring specification varies according to the
color of I.D. marks.
• Extent of adjustment (spring preload)
TIP
For the spring preload adjustment, refer to “AD-
JUSTING THE REAR SHOCK ABSORBER
ASSEMBLY” on page 3-30.
Type
Spring
rate
N/mm
Part numberI.D.
Mark
SOFT
52
1SL-22212-40
(Blue)
Yellow1SL-22212-50
(Red)
54
1SL-22212-60
(Blue)
Pink1SL-22212-70
(Red)
STD*56
1SL-22212-20
(Blue)
White1SL-22212-30
(Red)
STD58
1SL-22212-00
(Blue)
Silver1SL-22212-10
(Red)
STIFF60
1SL-22212-80
(Blue)
Brown1SL-22212-90
(Red)
MaximumMinimum
Position in which
the spring is turned
in 18 mm (0.71 in)
from its free length.Position in which
the spring is turned
in 1.5 mm (0.06 in)
from its free length.

CHASSIS
10-6
EAS1SL1377SUSPENSION SETTING (FRONT FORK)
TIP
• If any of the following symptoms is experienced with the standard position as the base, make reset-
ting by reference to the adjustment procedure given in the same chart.
• Before any change, set the rear shock absorber sunken length to the standard figure 90–100 mm
(3.5–3.9 in).
Symptom
Section
CheckAdjustJumpLarge
gapMedi-
um
gapSmall
gap
Stiff over entire
range
Compression
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.
Oil amountDecrease oil amount by about
5–10 cm3 (0.2–0.3 US oz, 0.2–
0.4 Imp.oz).
SpringReplace with soft spring.
Unsmooth
movement over
entire range
Outer tube
Inner tube
Check for any bends, dents,
other noticeable scars, etc. If
any, replace affected parts.
Slide metalReplace with a new one for ex-
tended use.
Piston metalReplace with a new one for ex-
tended use.
Lower bracket
tightening
torqueRetighten to specified torque.
Poor initial
movement
Rebound
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.
Oil sealsApply grease in oil seal wall.
Soft over entire
range, bottom
-
ing out
Compression
damping forceTurn adjuster clockwise (about
2 clicks) to increase damping.
Oil amountIncrease oil amount by about
5–10 cm3 (0.2–0.3 US oz, 0.2–
0.4 Imp.oz).
SpringReplace with stiff spring.
Stiff toward
stroke endOil amountDecrease oil amount by about
5 cm3 (0.2 US oz, 0.2 Imp.oz).
Soft toward
stroke end, bot
-
toming out
Oil amount
Increase oil amount by about 5
cm3 (0.2 US oz, 0.2 Imp.oz).
Stiff initial
movementCompression
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.

CHASSIS
10-7
EAS1SL1378SUSPENSION SETTING (REAR SHOCK ABSORBER)
TIP
• If any of the following symptoms is experienced with the standard position as the base, make reset-
ting by reference to the adjustment procedure given in the same chart.
• Adjust the rebound damping in 2-click increments or decrements.
• Adjust the low compression damping in 1-click increments or decrements.
• Adjust the high compression damping in 1/6 turn increments or decrements.
Low front, tend-
ing to lower
front posture
Compression
damping forceTurn adjuster clockwise (about
2 clicks) to increase damping.
Rebound
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.
Balance with
rear endSet sunken length for 95–100
mm (3.7–3.9 in) when one
passenger is astride seat (low
-
er rear posture).
Oil amountIncrease oil amount by about 5
cm3 (0.2 US oz, 0.2 Imp.oz).
”Obtrusive”
front, tending to
upper front pos
-
ture
Compression
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.
Balance with
rear endSet sunken length for 90–95
mm (3.5–3.7 in) when one
passenger is astride seat (up
-
per rear posture).
SpringReplace with soft spring.
Oil amountDecrease oil amount by about
5–10 cm3 (0.2–0.3 US oz, 0.2–
0.4 Imp.oz).
Symptom
Section
CheckAdjustJumpLarge
gapMedi-
um
gapSmall
gap
Stiff, tending to
sink
Rebound
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.
Spring set
lengthSet sunken length for 90–100
mm (3.5–3.9 in) when one
passenger is astride seat.
Spongy and un-
stable
Rebound
damping forceTurn adjuster clockwise (about
2 clicks) to increase damping.
Low compres-
sion damping
Turn adjuster clockwise (about
1 click) to increase damping.
SpringReplace with stiff spring.
SymptomSection
Check Adjust
JumpLarge
gapMedi-
um
gapSmall
gap

CHASSIS
10-8
Heavy and
dragging
Rebound
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.
SpringReplace with soft spring.
Poor road grip-
ping
Rebound
damping forceTurn adjuster counterclock-
wise (about 2 clicks) to de-
crease damping.
Low compres-
sion damping
Turn adjuster clockwise (about
1 click) to increase damping.
High compres-
sion damping
Turn adjuster clockwise (about
1/6 turn) to increase damping.
Spring set
lengthSet sunken length for 90–100
mm (3.5–3.9 in) when one
passenger is astride seat.
SpringReplace with soft spring.
Bottoming out
High compres-
sion damping
Turn adjuster clockwise (about
1/6 turn) to increase damping.
Spring set
lengthSet sunken length for 90–100
mm (3.5–3.9 in) when one
passenger is astride seat.
SpringReplace with stiff spring.
Bouncing
Rebound
damping forceTurn adjuster clockwise (about
2 clicks) to increase damping.
SpringReplace with soft spring.
Stiff travel
High compres-
sion damping
Turn adjuster counterclock-
wise (about 1/6 turn) to de-
crease damping.
Spring set
lengthSet sunken length for 90–100
mm (3.5–3.9 in) when one
passenger is astride seat.
SpringReplace with soft spring.
SymptomSection
Check Adjust
JumpLarge
gapMedi-
um
gapSmall
gap