2008 YAMAHA YFZ450 engine

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page 5-1 before riding for proper care of the ATV
and to ensure safety.
WARNING

EWB01430
Always inspect your ATV each time you use it
to make sure the ATV is in safe operating con-
dition. Always follow the inspection and main-
tenance procedures and schedules described
in the Owner’s Manual. Failure to inspect the
ATV before operating or failure to properly
maintain the ATV increases the possibility of
an accident or equipment damage.
WARNING

EWB01440
Always use the size and type tires specified in
the Owner’s Manual for this ATV on page 5-5.
Always maintain proper tire pressure as de-
scribed in the Owner’s Manual on page 5-6.
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 an accident.Do not operate at speeds too fast for your
skills or the conditions.WARNING
EWB01450
Always go at a speed that is proper for the ter-
rain, visibility and operating conditions, and
your experience. Operating this ATV at speeds
too fast for your skills or the conditions in-
creases your chances of losing control of the
ATV, which can result in an accident.
Speed limiter
For riders less experienced with this model, the
throttle lever housing is equipped with a speed lim-
iter. The speed limiter keeps the throttle from fully
opening, even when the throttle lever is pushed to
the maximum. Turning in the adjusting screw limits
the maximum engine power available and de-
creases the maximum speed of the ATV. Turning
in the adjusting screw decreases top speed, and
turning it out increases top speed. (See page 4-4.)

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WARNING

EWB01550
Always mount a caution flag on the ATV to
make you more visible when operating in areas
where you might not be seen by other vehicles.
Watch carefully for other vehicles.
Do not ride in areas posted “no trespassing”.
Do not ride on private property without getting per-
mission.Select a large, flat, unpaved area to become famil-
iar with your ATV. Make sure that this area is free
of obstacles and other riders. You should practice
control of the throttle, brakes, shifting procedures,
and turning techniques in this area before trying
more difficult terrain. Always avoid riding on paved
surfaces: the ATV is designed for use on unpaved
surfaces only, and handling maneuvers are more
difficult to perform on pavement.
Set the parking brake and follow the instruction on
page 6-1 to start the engine. Once it has warmed
up you are ready to begin riding your ATV. As you
get on the ATV, be sure not to accidentally move
the shift pedal. Remember that the engine and ex-
haust pipe will be hot when riding and afterwards;
do not allow skin or clothing to come in contact with

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these components.
With the engine idling, pull the clutch lever to dis-
engage the clutch and shift into 1st gear, and then
release the parking brake. Open the throttle grad-
ually, and at the same time, release the clutch le-
ver slowly. Once the ATV has attained adequate
speed, release the throttle lever and at the same
time, quickly pull in the clutch lever and shift into
2nd gear. Open the throttle part way and gradually
release the clutch. Use this same procedure as
you move into the higher gears. Be sure to coordi-
nate the use of the throttle and shift pedal properly.
If the throttle is applied too abruptly or if the throttle
is not released during shifting, or if the shift pedal
is not released before applying the throttle, the
front wheels may lift off the ground, resulting in a
loss of directional control. Avoid higher speeds un-
til you are thoroughly familiar with the operation of
your ATV.
WARNING

EWB01720
Always open the throttle gradually and release
the clutch lever slowly. Otherwise, the ATV
could wheelie which would increase the
chance of an accident.CAUTION:

ECB00230
Do not shift gears without releasing the throt-
tle. Damage to the engine or drive train may oc-
cur.
When slowing down or stopping, release the throt-
tle and apply the brakes smoothly and evenly. As
you slow down, shift to a lower gear. Be sure that
the engine has sufficiently slowed before engaging
a lower gear. Improper use of the brakes or shifting
can cause the tires to lose traction, reducing con-
trol and increasing the possibility of an accident.WARNING
EWB01560
Make sure the engine has sufficiently slowed
before shifting to a lower gear. Engaging a low-
er gear when the engine speed is too high
could cause the wheels to stop rotating.
TURNING YOUR ATV
To achieve maximum traction on unpaved surfac-
es, the two rear wheels are mounted solidly on one
axle and turn together at the same speed. There-
fore, unless the wheel on the inside of the turn is al-
lowed to slip or lose some traction, the ATV will
resist turning. A special turning technique must be

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EBU28781
PERIODIC MAINTENANCE AND MINOR REPAIR
EBU21670
Safety is an obligation of the owner. Periodic in-
spection, adjustment and lubrication will keep your
ATV in the safest and best operating condition
possible. The most important points of inspection,
adjustment, and lubrication are explained on the
following pages.
The intervals given in the periodic maintenance
and lubrication chart should be considered as a
general guide under normal riding conditions.
However, DEPENDING ON THE WEATHER,
TERRAIN, GEOGRAPHICAL LOCATION, AND
INDIVIDUAL USE, THE MAINTENANCE INTER-
VALS MAY NEED TO BE SHORTENED.
WARNING

EWB01840
Never service an engine while it is running.
Moving parts can catch clothing or parts of the
body, causing injury. Electrical components
can cause shocks or start fires. Turn off the en-
gine when performing maintenance unless
otherwise specified. Have a Yamaha dealer
perform the service if you are not familiar with
maintenance work.
EBU27110
Owner’s manual and tool kit
Be sure to put this owner’s manual in the plastic
bag and to always carry it as well as the owner’s
tool kit and the low-pressure tire gauge in their re-
spective compartments under the seat.
1. Low-pressure tire gauge
2. Owner’s tool kit
3. Owner’s manual
3 21

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EBU21742
Periodic maintenance chart for the emission control system
NOTE:


For ATVs not equipped with an odometer or an hour meter, follow the month maintenance intervals.

For ATVs equipped with an odometer or an hour meter, follow the km (mi) or hours maintenance inter-
vals. However, keep in mind that if the ATV isn’t used for a long period of time, the month maintenance
intervals should be followed.

Items marked with an asterisk should be performed by a Yamaha dealer as they require special tools,
data and technical skills.
NO. ITEMCHECK OR MAINTENANCE
JOBINITIAL EVERY
Whichev-
er comes
firstmonth 1 3 6 6 12
km
(mi)320
(200)1300
(800)2500
(1600)2500
(1600)5000
(3200)
hours 20 80 160 160 3201
*
Fuel line


Check fuel hoses for cracks or other damage, and
replace if necessary.
√√√
2 Spark plug

Check condition and clean, regap, or replace if
necessary.
√√√√√
3
*
Valves


Check valve clearance and adjust if necessary.
√ √√√
4
*
Carburetor


Check starter (choke) operation and correct if nec-
essary.

Check engine idling speed and adjust if neces-
sary.
√√√√
5
*
Crankcase breather
system


Check breather hose for cracks or other damage,
and replace if necessary.
√√√

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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

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20 Engine oil

Change.

Check ATV for oil leakage, and correct if neces-
sary.
√ √√√
21Engine oil filter ele-
ment

Clean or replace if necessary.
√√√
22 Cooling system

Check coolant level and ATV for coolant leakage,
and correct if necessary.
√√√√√

Replace coolant. Every 2 years
23
*
Moving parts and
cables

Lubricate.
√√√√
24
*
Throttle lever hous-
ing and cable


Check operation and correct if necessary.

Check throttle cable free play and adjust if neces-
sary.

Lubricate throttle lever housing and cable.
√√√√√
25
*
Front and rear brake
switches

Check operation and correct if necessary.
√√√√√
26
*
Lights and switches

Check operation and correct if necessary.

Adjust headlight beams.
√√√√√
NO. ITEMCHECK OR MAINTENANCE
JOBINITIAL EVERY
Whichev-
er comes
firstmonth 1 3 6 6 12
km
(mi)320
(200)1300
(800)2500
(1600)2500
(1600)5000
(3200)
hours 20 80 160 160 320

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To install the panel1. Place the panel in the original position, and
then install the quick fastener screw and the
bolts.
2. Install the seat.
EBU23241
Checking the spark plug
The spark plug is an important engine component,
which is easy to check. Since heat and deposits
will cause any spark plug to slowly erode, the spark
plug should be removed and checked in accor-
1. Bolt
1

1. Projection
2. Slot
1
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