2008 YAMAHA YFZ450 suspension

4-12
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EBU27903
Adjusting the front shock absorber
assemblies
These shock absorber assemblies are equipped
with a spring preload adjusting nut, a rebound
damping force adjusting screw, with a compres-
sion damping force adjusting bolt (for fast com-
pression damping), and a compression damping
force adjusting screw (for slow compression damp-
ing).
WARNING
EWB00410
These 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.
Spring preload
1. Loosen the locknut.
2. Turn the adjusting nut in direction (a) to in-
crease the spring preload and thereby harden
the suspension, and in direction (b) to de-
crease the spring preload and thereby soften
1. Projection
2. Seat holder
1
2

4-13
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the suspension.
NOTE:


A special wrench can be obtained at a Yamaha
dealer to make this adjustment.

The spring preload setting is determined by
measuring distance A, shown in the illustration.
The shorter distance A is, the higher the spring
preload; the longer distance A is, the lower the
spring preload. With each complete turn of the
adjusting nut, distance A is changed by 1.5 mm
(0.06 in).
1. Spring preload adjusting nut
2. Locknut
3. Special wrench
2
1
3 (a)
(b)

Spring preload setting:
Minimum (hard):
Distance A = 246.5 mm (9.70 in)
Standard:
Distance A = 255.0 mm (10.04 in)
Maximum (soft):
Distance A = 261.5 mm (10.30 in)
1. Distance A
1

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CAUTION:
ECB00090
Never turn an adjusting mechanism beyond
the minimum and maximum settings.
NOTE:

Although the total number of clicks of a damping
force adjusting mechanism may not exactly match
the above specifications due to small differences in
production, the actual number of clicks always rep-
resents the entire adjusting range. To obtain a pre-
cise adjustment, it would be advisable to check the
number of clicks of each damping force adjusting
mechanism and to modify the specifications as
necessary.WARNING
EWB00420

Suspension components become hot during
operation. Never touch the compression
damping force adjusting screw, the rebound
damping force adjusting screw or the oil res-
ervoir with your bare hand or skin until sus-
pension components have cooled.

Always adjust the shock absorber assem-
blies on the left and right side to the same
1. Compression damping force adjusting screw (for slow
compression damping)
Compression damping setting (for slow com-
pression damping):
Minimum (soft):
20 click(s) in direction (b)*
Standard:
10 click(s) in direction (b)*
Maximum (hard):
1 click(s) in direction (b)*
* With the adjusting screw fully turned in di-
rection (a)
(b)(a)
1

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4. Loosen the locknut.
5. Turn the adjusting nut in direction (a) to in-
crease the spring preload and thereby harden
the suspension, and in direction (b) to de-
crease the spring preload and thereby soften
the suspension.NOTE:

A special wrench can be obtained at a Yamaha
dealer to make this adjustment.

The spring preload setting is determined by
measuring distance A, shown in the illustration.
The shorter distance A is, the higher the spring
preload; the longer distance A is, the lower the
spring preload. With each complete turn of the
adjusting nut, distance A is changed by 1.5 mm
1. Bolt
2. Air filter case
2 1

1. Spring preload adjusting nut
2. Locknut
3. Special wrench
2
1
(a)
(b)
3

4-23
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CAUTION:
ECB00090
Never turn an adjusting mechanism beyond
the minimum and maximum settings.NOTE:

Although the total number of clicks of a damping
force adjusting mechanism may not exactly match
the above specifications due to small differences in
production, the actual number of clicks always rep-
resents the entire adjusting range. To obtain a pre-
cise adjustment, it would be advisable to check the
number of clicks of each damping force adjusting
mechanism and to modify the specifications as
necessary.
3. Install the seat.WARNING
EWB00440
Suspension components become hot during
operation. Never touch the compression
damping force adjusting screw, the rebound
damping force adjusting screw or the oil reser-
voir with your bare hand or skin until suspen-
sion components have cooled.
1. Compression damping force adjusting screw (for slow
compression damping)
Compression damping setting (for slow com-
pression damping):
Minimum (soft):
20 click(s) in direction (b)*
Standard:
11 click(s) in direction (b)*
Maximum (hard):
1 click(s) in direction (b)*
* With the adjusting screw fully turned in di-
rection (a)
(b)(a)
1

8-6
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78
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11

10
*
Swingarm pivots

Check operation and for excessive play, and
replace bearings if necessary.

Lubricate with molybdenum disulfide grease.
√√√
11
*
Upper and lower
arm pivots


Lubricate with lithium-soap-based grease.
√√√
12 Drive chain

Check chain slack and adjust if necessary.

Check rear wheel alignment and correct if necess-
sary.

Clean and lubricate.
√√√√√
13
*
Drive chain rollers


Check for wear and replace if necessary.
√√√
14
*
Chassis fasteners


Make sure that all nuts, bolts, and screws are
properly tightened.
√√√√√
15
*
Shock absorber
assemblies


Check operation and correct if necessary.

Check for oil leakage and replace if necessary.
√√√
16
*
Rear suspension
relay arm and con-
necting arm pivot-
ing points


Check operation and correct if necessary.

Lubricate with lithium-soap-based grease.
√√√√
17
*
Steering shaft


Lubricate with lithium-soap-based grease.
√√√
18
*
Steering system


Check operation and repair or replace if damaged.

Check toe-in and adjust if necessary.
√√√√√
19
*
Engine mount


Check for cracks or other damage, and replace if
necessary.
√√√
NO. ITEMCHECK OR MAINTENANCE
JOBINITIAL EVERY
Whichev-
er comes
firstmonth136612
km
(mi)320
(200)1300
(800)2500
(1600)2500
(1600)5000
(3200)
hours 20 80 160 160 320

10-4
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2
3
4
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910
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Rear brake:

Type:
Single disc brake
Operation:
Right foot operation
Recommended fluid:
DOT 4
Front suspension:
Type:
Double wishbone
Spring/shock absorber type:
Coil spring/gas-oil damper
Wheel travel:
230 mm (9.1 in)
Rear suspension:
Type:
Swingarm (link suspension)
Spring/shock absorber type:
Coil spring/gas-oil damper
Wheel travel:
270 mm (10.6 in)
Electrical system:
Ignition system:
DC. CDI
Charging system:
AC magneto
Battery:
Model:
GT7B-4
Voltage, capacity:
12 V, 6.5 Ah
Headlight:
Bulb type:
Krypton bulb
Bulb voltage, wattage x quantity:
Headlight:
12 V, 30.0/30.0 W
×
2
Tail/brake light:
12 V, 0.5/3.9 W
×
1
Neutral indicator light:
12 V, 1.7 W
×
1
Coolant temperature warning light:
12 V, 1.7 W
×
1

Fuses:
Main fuse:
15.0 A

L
Label locations ................................................................2-1
Light switch .....................................................................4-3
M
Main switch .....................................................................4-1
Maintenance and lubrication chart ..................................8-5
Maintenance chart, emission control system ..................8-3
Model label....................................................................11-2
N
Neutral indicator light ......................................................4-1
O
Owner’s manual and tool kit............................................8-1
P
Panel, removing and installing ........................................8-9
Parking ............................................................................6-5
Parking brake free play, adjusting.................................8-37
Parking brake lever .........................................................4-6
Parking on a slope ..........................................................6-6
Part locations ..................................................................3-1
Pre-operation check list ..................................................5-1
R
Riding your ATV ..............................................................7-1
S
Safety information ...........................................................1-1
Seat...............................................................................4-11
Shifting ............................................................................6-3
Shift pedal .......................................................................4-7
Shock absorber assemblies, adjusting the front ...........4-12
Shock absorber assembly, adjusting the rear ...............4-17
Spark arrester, cleaning ................................................8-28
Spark plug, checking.....................................................8-10Specifications ............................................................... 10-1
Speed limiter .................................................................. 4-4
Starter (choke) ............................................................. 4-10
Start switch .................................................................... 4-3
Storage .......................................................................... 9-2
Suspension, lubricating the upper and lower arm
pivots ......................................................................... 8-44
Swingarm pivots, lubricating ........................................ 8-43
T
Tail/brake light bulb, replacing ..................................... 8-50
Throttle cable free play, adjusting ................................ 8-30
Throttle lever ...........................................................4-3
,
5-5
Tire pressure, measuring ............................................... 5-6
Tires ............................................................................... 5-5
Tire wear limit................................................................. 5-7
Troubleshooting ........................................................... 8-51
Troubleshooting charts ................................................ 8-52
V
Valve clearance ........................................................... 8-31
Vehicle identification number ....................................... 11-1
W
Wheel hub bearings, checking ..................................... 8-43
Wheel, installing ........................................................... 8-50
Wheel, removing .......................................................... 8-50