YAMAHA YFZ450 2008 Service Manual

4-19
1
2
34
5
6
7
8
9
10
11

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

4-20
1
2
34
5
6
7
8
9
10
11

(0.06 in). 6. Tighten the locknut to the specified torque.CAUTION:
ECB00080
Always tighten the locknut against the adjust-
ing nut, and then tighten it to the specified
torque.
7. Place the air filter case in the original position,
connect the air intake duct, and then tighten
the clamp screw at the carburetor side.
8. Install the bolts, and then connect the hose.
9. Install the seat.
Rebound damping force
Turn the adjusting screw in direction (a) to increase
the rebound damping force and thereby harden
the damping, and in direction (b) to decrease the
rebound damping force and thereby soften the
damping. Spring preload setting:
Minimum (hard):
Distance A = 250.0 mm (9.84 in)
Standard:
Distance A = 257.0 mm (10.12 in)
Maximum (soft):
Distance A = 265.0 mm (10.43 in)

1. Distance A
1

Tightening torque:
Locknut:
44 Nm (4.4 m·kgf, 33 ft·lbf)

4-21
1
2
34
5
6
7
8
9
10
11
NOTE:

Make sure that the position indicator marks are
aligned when the shock absorber assembly is set
to the standard setting.
Compression damping force
Compression damping force (for fast compressiondamping)1. Remove the seat. (See page 4-11.)
2. To increase the compression damping force
and thereby harden the compression damp-
ing, turn the adjusting bolt in direction (a). To
decrease the compression damping force and
thereby soften the compression damping, turn
the adjusting bolt in direction (b).

1. Position indicator marks
2. Rebound damping force adjusting screw
Rebound damping setting:
Minimum (soft):
3 turn(s) out from the fully turned in position
Standard:
1 1/2 turn(s) out from the fully turned in po-
sition
Maximum (hard):
Fully turned in
21
(b)
(a)

4-22
1
2
34
5
6
7
8
9
10
11

3. Install the seat.NOTE:

Make sure that the position indicator marks are
aligned when the shock absorber assembly is set
to the standard setting.
Compression damping force (for slow compres-
sion damping)1. Remove the seat. (See page 4-11.)
2. To increase the compression damping force
and thereby harden the compression damp-
ing, turn the adjusting screw in direction (a).
To decrease the compression damping force
and thereby soften the compression damping,
turn the adjusting screw in direction (b).

1. Compression damping force adjusting bolt (for fast com-
pression damping)
2. Position indicator marks
Compression damping setting (for fast com-
pression damping):
Minimum (soft):
3 turn(s) out from the fully turned in position
Standard:
2 turn(s) out from the fully turned in position
Maximum (hard):
Fully turned in
(b)(a)
1
2
1

4-23
1
2
34
5
6
7
8
9
10
11
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

5-1
1
2
3
45
6
7
8
9
10
11

EBU19200
PRE-OPERATION CHECKS
EBU19220
Pre-operation check list
Before operating this ATV, be sure to check the items listed in the following table.
NOTE:

The maintenance of some items in the table has to be performed by a Yamaha dealer. Refer to the “Periodic
maintenance and lubrication chart” on page 8-3 to determine which service should be performed by a
Yamaha dealer.
ITEM ROUTINE PAGE
Fuel


Check fuel level in fuel tank, and add recommended fuel if neces-
sary.

Check fuel line for leakage. Correct if necessary.4-8, 5-4
Engine oil

Check oil level in engine, and add recommended oil to specified
level if necessary.

Check ATV for oil leakage. Correct if necessary.5-4, 8-14
Coolant

Check coolant level in reservoir, and add recommended coolant to
specified level if necessary.

Check cooling system for leakage. Correct if necessary.5-4, 8-20
Front brake

Check operation. If soft or spongy, have Yamaha dealer bleed
hydraulic system.

Check brake pads for wear, and replace if necessary.

Check brake fluid level in reservoir, and add recommended brake
fluid to specified level if necessary.

Check hydraulic system for leakage. Correct if necessary.5-4, 8-31, 8-32, 8-36

5-2
1
2
3
45
6
7
8
9
10
11

Rear brake

Check operation. If soft or spongy, have Yamaha dealer bleed
hydraulic system.

Check brake pads for wear, and replace if necessary.

Check brake fluid level in reservoir, and add recommended brake
fluid to specified level if necessary.

Check hydraulic system for leakage. Correct if necessary.5-4, 8-31, 8-32, 8-36
Clutch

Check operation, and correct if necessary.

Lubricate cable if necessary.

Check lever free play, and adjust if necessary.8-39
Throttle lever

Make sure that operation is smooth. Lubricate cable and lever hous-
ing if necessary.

Check cable free play, and adjust if necessary.5-5, 8-30
Control cables

Make sure that operation is smooth. Lubricate if necessary. 8-41
Drive chain

Check chain slack, and adjust if necessary.

Check chain condition. Lubricate if necessary.5-5, , 8-41
Wheels and tires

Check wheel condition, and replace if damaged.

Check tire condition and tread depth. Replace if necessary.

Check air pressure. Correct if necessary.5-5, 5-6, 5-7
Brake and shift pedals

Make sure that operation is smooth. Lubricate pedal pivoting points
if necessary.8-43
Brake and clutch levers

Make sure that operation is smooth. Lubricate lever pivoting points
if necessary.8-42
Chassis fasteners

Make sure that all nuts, bolts and screws are properly tightened. 5-8
Instruments, lights and
switches

Check operation, and correct if necessary. 5-8
ITEM ROUTINE PAGE

5-3
1
2
3
45
6
7
8
9
10
11
WARNING

EWB00480
Always inspect your ATV each time you use it to make sure it is in safe operating condition.
Always follow the inspection and maintenance procedures and schedules described in the Owner’s
Manual. Failure to inspect increases the possibility of an accident or equipment damage.

5-4
1
2
3
45
6
7
8
9
10
11

EBU19540
Fuel
Make sure that there is sufficient fuel in the tank.
(See page 4-8.)
WARNING

EWB00520

Do not overfill the fuel tank. Fuel expands
when it heats up. If the fuel tank is overfilled,
fuel could spill out due to heat from the en-
gine or the sun.

Be careful not to spill fuel, especially on the
engine or exhaust pipe which can cause a
fire and severe injury. Wipe up any spilled
fuel immediately.

Do not refuel right after the engine has been
running and is still very hot.

Be sure the fuel tank cap is closed securely.
EBU19560
Engine oil
Make sure that the engine oil is at the specified lev-
el. Add oil as necessary.
EBU19630
Coolant
Make sure that the coolant is at the specified level.
Add coolant as necessary. (See page 8-20.)
NOTE:

The coolant level must be checked on a cold en-
gine since the level varies with engine tempera-
ture.
WARNING

EWB00510
Wait for the engine and radiator to cool before
removing the radiator cap. You could be
burned by hot fluid and steam blown out under
pressure. Always put a thick rag over the cap
when opening. Allow any remaining pressure
to escape before completely removing the cap.
EBU19710
Front and rear brakes
Brake lever and brake pedal

Check that there is no free play in the brake le-
ver. If there is free play, have a Yamaha dealer
check the brake system.

Check for correct brake pedal height. (See
page 8-36.) If the pedal height is incorrect, have
a Yamaha dealer adjust it.

Check the operation of the lever and pedal. They
should move smoothly and there should be a
firm feeling when the brakes are applied. If not,

5-5
1
2
3
45
6
7
8
9
10
11

have a Yamaha dealer check the brake system.
Brake fluid level
Check the brake fluid level. Add fluid if necessary.
(See page 8-32.)
Brake fluid leakage
Check to see if any brake fluid is leaking out of the
pipe joints or brake fluid reservoirs. Apply the
brakes firmly for one minute. If there is any leak-
age, have a Yamaha dealer check the brake sys-
tem.
Brake operation
Test the brakes at slow speed after starting out to
make sure they are working properly. If the brakes
do not provide proper braking performance, check
the brake pads for wear. (See page 8-31.)
WARNING

EWB00580
Always check the brakes at the start of every
ride. Do not ride the ATV if you find any prob-
lem with the brakes or you could lose braking
ability, which could lead to an accident. If aproblem cannot be corrected by the adjust-
ment procedures provided in this manual, have
a Yamaha dealer check for the cause.
EBU19761
Throttle lever
Check the operation of the throttle lever. It must
open smoothly and spring back to the idle position
when released. Have a Yamaha dealer correct if
necessary.
EBU19770
Drive chain
Check the condition of the drive chain and check
the drive chain slack. Lubricate and adjust the
drive chain as necessary.
EBU19791
Tires
WARNING

EWB00601
Use of improper tires on this ATV, or operation
of this ATV with improper or uneven tire pres-
sure, may cause loss of control, increasing
your risk of accident.
Pay attention to the following.

The tires listed below have been approved
Recommended brake fluid:
DOT 4