2008 YAMAHA YZ450F Owners Manual

7-8
CHASSIS
does not exceed the standard as it
may result in faulty performance.
Never use one whose overall
length is greater than standard.
REAR SHOCK ABSORBER
SETTING PARTS
• Rear shock spring "1"
[Equal-pitch titanium spring]
[Equal-pitch steel spring][Unequal-pitch steel spring]
Install the spring seat "2" to the ti-
tanium spring.
• The unequal-pitch spring is softer in
initial characteristic than the equal-
pitch spring and is difficult to bottom
out under full compression.
• The I.D. mark "a" is marked at the
end of the spring.
• Spring specification varies accord-
ing to the color and quantity of I.D.
marks.
• Extent of adjustment (spring length)[Titanium spring]
[Steel spring] Length "a" of standard
shock:
490 mm (19.29 in)
T
Y
P
ESPRI
NG
RAT
ESPRING
PART
NUM-
B E R
(-22212-)I.D.
MARKSPR
ING
FRE
E
LEN
GTH
(ap-
prox
.)
S
O
F
T4.5 1C3-00 Green 265
4.7 1C3-10 Red 265
4.9 1C3-20 Black 265
5.1 1C3-30 Blue 265
5.3 1C3-40 Yellow 275
S
T
D5.51C3-50
(1C3-B0)Pink 275
S
TI
F
F
5.71C3-60White275
T
Y
P
ESPRI
NG
RAT
ESPRING
PART
NUM-
BER
(-22212-)I.D.
MARK/
Q'TYSPR
ING
FRE
E
LEN
GTH
4.3 5UN-00 Brown/1 260
T
Y
P
ESPRI
NG
RAT
E
(ap-
prox.
)SPRING
PART
NUM-
B E R
(-22212-)I.D.
MARK/
Q'TYSPR
ING
FRE
E
LEN
GTH
S
O
F
T4.5 5UN-A0 Green/2 275
4.7 5UN-B0 Red/2 275
4.9 5UN-C0 Black/2 275
5.1 5UN-D0 Blue/2 275
5.3 5UN-E0Yellow/
2275
5.5 5UN-F0 Pink/2 275
S
TI
F
F5.7 5UN-G0 White/2 275
SPRING
FREE
LENGTHEXTENT OF AD-
JUSTMENT "b"
Approx.
265 mm
(10.43 in)One I.D. mark
245.5–263.5 mm
(9.67–10.37 in)
Two I.D. marks
251.5–269.5 mm
(9.90–10.61 in)
Three I.D. marks
243.0–261.0 mm
(9.57–10.28 in)
Approx.
275 mm
(10.83 in)One I.D. mark
255.5–273.5 mm
(10.06–10.77 in)
Two I.D. marks
261.5–279.5 mm
(10.30–11.00 in)
Three I.D. marks
253.0–271.0 mm
(9.96–10.67 in)
SPRING
FREE
LENGTHEXTENT OF AD-
JUSTMENT "b"
260 mm
(10.24 in)240.5–258.5 mm
(9.47–10.18 in)
275 mm
(10.83 in)255.5–273.5 mm
(10.06–10.77 in)

7-9
CHASSIS
SUSPENSION SETTING (FRONT FORK)
• If any of the following symptoms is experienced with the standard position as the base, make resetting 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).
SymptomSection
Check Adjust
JumpLarge
gapMedi-
um
gapSmall
gap
Stiff over entire
range
○○○
Compression damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Oil amount Decrease oil amount by about 5–10 cm
3 (0.2–0.4
Imp oz, 0.2–0.3 US oz).
Spring Replace with soft spring.
Unsmooth move-
ment over entire
range
○○○○
Outer tube Check for any bends, dents, and other noticeable
scars, etc. If any, replace affected parts.
Inner tube
Slide metal Replace with a new one for extended use.
Piston metal Replace with a new one for extended use.
Under bracket tighten-
ing torqueRetighten to specified torque.
Poor initial move-
ment
○
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Oil seal Apply grease in oil seal wall.
Soft over entire
range, bottoming
out
○○
Compression damping Turn adjuster clockwise (about 2 clicks) to in-
crease damping.
Oil amount Increase oil amount by about 5–10 cm
3 (0.2–0.4
Imp oz, 0.2–0.3 US oz).
Spring Replace with stiff spring.
Stiff toward stroke
end
○Oil amountDecrease oil amount by about 5 cm3 (0.2 Imp
oz,0.2 US oz).
Soft toward stroke
end, bottoming out
○Oil amountIncrease oil amount by about 5 cm3 (0.2 Imp
oz,0.2 US oz).
Stiff initial move-
ment
○○○○Compression dampingTurn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Low front, tending to
lower front posture
○○
Compression damping Turn adjuster clockwise (about 2 clicks) to in-
crease damping.
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Balance with rear end Set sunken length for 95–100 mm (3.7–3.9 in)
when one passenger is astride seat (lower rear
posture).
Oil amount Increase oil amount by about 5 cm
3 (0.2 Imp oz,
0.2 US oz).
"Obtrusive" front,
tending to upper
front posture
○○
Compression damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Balance with rear end Set sunken length for 90–95 mm (3.5–3.7 in)
when one passenger is astride seat (upper rear
posture).
Spring Replace with soft spring.
Oil amount Decrease oil amount by about 5–10 cm
3 (0.2–0.4
Imp oz, 0.2–0.3 US oz).

7-10
CHASSIS
SUSPENSION SETTING (REAR SHOCK ABSORBER)
• If any of the following symptoms is experienced with the standard position as the base, make resetting 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.
SymptomSection
Check Adjust
JumpLarge
gapMedi-
um
gapSmall
gap
Stiff, tending to sink
○○
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Spring set length Set sunken length for 90–100 mm (3.5–3.9 in)
when one passenger is astride seat.
Spongy and unsta-
ble
○○
Rebound damping Turn adjuster clockwise (about 2 clicks) to in-
crease damping.
Low compression
dampingTurn adjuster clockwise (about 1 click) to increase
damping.
Spring Replace with stiff spring.
Heavy and dragging
○○
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Spring Replace with soft spring.
Poor road gripping
○
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Low compression
dampingTurn adjuster clockwise (about 1 clicks) to in-
crease damping.
High compression
dampingTurn adjuster clockwise (about 1/6 turn) to in-
crease damping.
Spring set length Set sunken length for 90–100 mm (3.5–3.9 in)
when one passenger is astride seat.
Spring Replace with soft spring.
Bottoming out
○○
High compression
dampingTurn adjuster clockwise (about 1/6 turn) to in-
crease damping.
Spring set length Set sunken length for 90–100 mm (3.5–3.9 in)
when one passenger is astride seat.
Spring Replace with stiff spring.
Bouncing
○○
Rebound damping Turn adjuster clockwise (about 2 clicks) to in-
crease damping.
Spring Replace with soft spring.
Stiff travel
○○
High compression
dampingTurn adjuster counterclockwise (about 1/6 turn) to
decrease damping.
Spring set length Set sunken length for 90–100 mm (3.5–3.9 in)
when one passenger is astride seat.
Spring Replace with soft spring.

PRINTED IN JAPAN
(E) PRINTED ON RECYCLED PAPER YAMAHA MOTOR CO., LTD.
2500 SHINGAI IWATA SHIZUOKA JAPAN