YAMAHA YFZ450 2008 Owners Manual

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EBU27701
Cleaning the spark arrester
Select a well-ventilated area free of combustible
materials and make sure the exhaust and muffler
are cool.
1. Remove the bolt.
2. Remove the tailpipe by pulling it out of the
muffler.
3. Tap the tailpipe lightly, and then use a wire
brush to remove any carbon deposits from the
spark arrester portion of the tailpipe and inside
of the tailpipe housing.4. Insert the tailpipe into the muffler and align the
bolt holes.
5. Install the bolt and tighten it to the specified
torque.
6. Remove the purging bolt.
1. Bolt
1

1. Tailpipe
2. Spark arrester
Tightening torque:
Tailpipe bolt:
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
1
2

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7. Start the engine and rev it up approximately
twenty times while momentarily creating ex-
haust system back pressure by blocking the
end of the muffler with a shop towel.
8. Stop the engine and allow the exhaust pipe to
cool.
9. Install the purging bolt and tighten it to the
specified torque.
WARNING

EWB02380
Never run the engine in an enclosed area when
purging the spark arrester, otherwise it could
cause injury to the eyes, burns, carbon monox-
ide poisoning, possibly leading to death, and
start a fire.

Always let the exhaust system cool prior to
touching exhaust components.

Always wear eye protection, and make sure
no one is behind the ATV.

Make sure there are no combustible materi-
als in the area.
EBU23940
Adjusting the carburetor
The carburetor should be checked and, if neces-
sary, adjusted at the intervals specified in the peri-
odic maintenance and lubrication chart. The
carburetor is an important part of the engine and
requires very sophisticated adjustment. Therefore,
most carburetor adjustments should be left to a
Yamaha dealer, who has the necessary profes-
sional knowledge and experience. The adjustment
described in the following section, however, may
be performed by the owner as part of routine main-
1. Purging bolt
2. Gasket
Tightening torque:
Purging bolt:
27 Nm (2.7 m·kgf, 20 ft·lbf)
1 2

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tenance.
CAUTION:

ECB00480
The carburetor has been set and extensively
tested at the Yamaha factory. Changing these
settings without sufficient technical knowl-
edge may result in poor performance of or
damage to the engine.
EBU24030
Checking the engine idling speed
A special tester is needed to check the engine
idling speed on this model.
Therefore, take the ATV to a Yamaha dealer to
have the engine idling speed checked and adjust-
ed.
EBU24043
Adjusting the throttle cable free play
The throttle cable free play should be checked
and, if necessary, adjusted at the intervals speci-
fied in the periodic maintenance and lubrication
chart.
The throttle cable free play should measure 2.0–4.0 mm (0.08–0.16 in) at the throttle lever. Period-
ically check the throttle cable free play and, if nec-
essary, adjust it as follows.
NOTE:

The engine idling speed must be checked, and ad-
justed if necessary, before adjusting the throttle ca-
ble free play.
1. Loosen the locknut.
2. To increase the throttle cable free play, turn
the adjusting bolt in direction (a). To decrease
the throttle cable free play, turn the adjusting
bolt in direction (b).
Engine idling speed:
1750–1850 r/min

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3. Tighten the locknut.
EBU24060
Valve clearance
The valve clearance changes with use, resulting in
improper air-fuel mixture and/or engine noise. To
prevent this from occurring, the valve clearance
must be adjusted by a Yamaha dealer at the inter-
vals specified in the periodic maintenance and lu-
brication chart.
EBU24130
Checking the front and rear brake pads
The front and rear brake pads must be checked for
wear at the intervals specified in the periodic main-
tenance and lubrication chart.
EBU27711
Front brake pads
Each brake pad is provided with wear indicator
grooves, which allow you to check the brake pad
wear without having to disassemble the brake. To
check the brake pad wear, check the wear indica-
tor grooves. If a brake pad has worn to the point
that the wear indicator grooves are almost in con-
tact with the disc plate, have a Yamaha dealer re-
place the brake pads as a set.
1. Locknut
2. Throttle cable free play adjusting bolt
3. Throttle lever free play
3 2
1
(a)(b)

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NOTE:

The wheels need to be removed to check the
brake pads. (See page 8-50.)
EBU27721
Rear brake pads
Each brake pad is provided with wear indicator
grooves, which allow you to check the brake pad
wear without having to disassemble the brake. To
check the brake pad wear, check the wear indica-
tor grooves. If a brake pad has worn to the point
that the wear indicator grooves are almost in con-
tact with the disc plate, have a Yamaha dealer re-place the brake pads as a set.
EBU26831
Checking the brake fluid level
Insufficient brake fluid may allow air to enter the
brake system, possibly causing it to become inef-
fective.
Before riding, check that the brake fluid is above
the minimum level mark and replenish if neces-
sary. A low brake fluid level may indicate worn
brake pads and/or brake system leakage. If the
brake fluid level is low, be sure to check the brake
pads for wear and the brake system for leakage.
1. Wear indicator groove
1

1. Wear indicator groove1

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Front brake Rear brake
NOTE:
To check the rear brake fluid level, remove the
seat. (See page 4-11.)
If the rear brake fluid level is low, replenish as fol-
lows.
1. Remove the brake fluid reservoir bracket bolt.
1. Minimum level mark
1

1. Minimum level mark
1

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2. Pull the brake fluid reservoir out to the side as
shown.CAUTION:
ECB00780
Do not tilt the rear brake fluid reservoir exces-
sively when removing or installing the rear
brake fluid reservoir. Also do not twist or pull
the hose of the reservoir.
3. Remove the brake fluid reservoir cap, and
then refill with brake fluid.
4. Install the brake fluid reservoir cap.
5. Insert the projection on the brake fluid reser-
voir bracket into the hole in the frame.
1. Bolt
1

1. Brake fluid reservoir cap
1

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6. Install the brake fluid reservoir bracket bolt.
Observe these precautions:

When checking the fluid level, make sure that
the top of the brake fluid reservoir is level.

Use only the recommended quality brake fluid,
otherwise the rubber seals may deteriorate,
causing leakage and poor braking performance.

Refill with the same type of brake fluid. Mixing
fluids may result in a harmful chemical reaction
and lead to poor braking performance.

Be careful that water does not enter the brake
fluid reservoir when refilling. Water will signifi-
cantly lower the boiling point of the fluid and may
result in vapor lock.

Brake fluid may deteriorate painted surfaces or
plastic parts. Always clean up spilled fluid imme-
diately.

As the brake pads wear, it is normal for the brake
fluid level to gradually go down. However, if the
brake fluid level goes down suddenly, have a
Yamaha dealer check the cause.
EBU24290
Changing the brake fluid
Have a Yamaha dealer change the brake fluid at
the intervals specified in the NOTE after the peri-
odic maintenance and lubrication chart. In addi-
tion, have the oil seals of the master cylinders and
calipers as well as the brake hoses replaced at the
intervals listed below or whenever they are dam-
aged or leaking.

Oil seals: Replace every two years.

Brake hoses: Replace every four years.
1. Frame
2. Projection
3. Brake fluid reservoir bracket
4. Bolt
Recommended brake fluid:
DOT 4
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EBU24390
Checking the front brake lever free play
The brake lever free play must be checked at the
intervals specified in the periodic maintenance and
lubrication chart. The brake lever should have a
free play of zero mm (zero in) as shown. If the free
play is incorrect, have a Yamaha dealer check the
brake system.
WARNING

EWB02070
Operating with improperly serviced or adjust-
ed brakes could cause loss of braking ability,
which could lead to an accident.After servicing:

Make sure the brakes operate smoothly and
that the free play is correct.

Make sure the brakes do not drag.

Make sure the brakes are not spongy. All air
must be bled from the brake system.
Replacement of brake components requires
professional knowledge. These procedures
should be performed by a Yamaha dealer.
EBU24611
Checking the brake pedal position
The brake pedal position must be checked and, if
necessary, adjusted at the intervals specified in
the periodic maintenance and lubrication chart.
The top of the brake pedal should be positioned
11.7 mm (0.46 in) below the top of the footrest as
shown. If the brake pedal is not positioned as spec-
ified, have a Yamaha dealer adjust it.
1. Brake lever free play
1

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WARNING

EWB02110
Operating with improperly serviced or adjust-
ed brakes could cause loss of braking ability,
which could lead to an accident.
After servicing:

Make sure the brakes operate smoothly and
that the brake pedal position is correct.

Make sure the brakes do not drag.

Make sure the brakes are not spongy. All air
must be bled from the brake system.
Replacement of brake components requires
professional knowledge. These procedures
should be performed by a Yamaha dealer.
EBU24710
Adjusting the parking brake free play
The parking brake free play must be checked and,
if necessary, adjusted at the intervals specified in
the periodic maintenance and lubrication chart.
Cable length “A” should measure 47–51 mm (1.9–
2.0 in). Adjust the parking brake free play as fol-
lows.
1. Release the parking brake by moving the
1. Brake pedal position
1

1. Adjusting bolt
2. Cable length “A”
3. Locknut
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