engine YAMAHA YFZ450 2012 User Guide

4-4
4
Regulate the speed of the ATV by varying the
throttle position. Because the throttle is spring-
loaded, the ATV will decelerate, and the engine will
return to an idle any time the throttle lever is re-
leased.
Before starting the engine, check the throttle to be
sure it is operating smoothly. Make sure it returns
to the idle position as soon as the lever is released.
EBU18323Speed limiter Your ATV is equipped with an adjustable speed
limiter. The speed limiter keeps the throttle from
fully opening, even when the throttle lever is
pushed to the maximum.
1. Loosen the locknut.
2. To increase the maximum engine power avail- able and the maximum speed of the ATV, turn
the adjusting screw in direction (a). To de-
crease the maximum engine power available
and the maximum speed of the ATV, turn the
adjusting screw in direction (b). Do not turn
the adjusting screw out more than 12 mm
(0.47 in) or the throttle cable could be dam-
aged. Always make sure the throttle lever free
play is adjusted to 2.0– 4.0 mm (0.08–0.16 in).
(See page 8-31.) WARNING! Improper ad-
justment of the speed limiter and throttle
could cause throttle cable damage or im-
proper throttle operation. You could lose
control, resulting in an accident.
[EWB00241]
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4
EBU18432Brake pedal The brake pedal is located on the right side of the
ATV. To apply the rear brake, push down on the
brake pedal.
EBU18520Parking brake lever Use the parking brake before starting the engine or
parking the ATV, especially on a slope. To apply
the parking brake, move the parking brake lever in
direction (a). To release the parking brake, move
the parking brake lever in direction (b).
1. Brake lever
1
1. Brake pedal
1
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4
WARNING
EWB00220
Always set the parking brake before starting
the engine. The ATV could start moving un-
expectedly if the parking brake is not ap-
plied. This could cause loss of control or a
collision.
Always be sure you have released the park-
ing brake before you begin to ride. The brake
could overheat if you ride the ATV without re-
leasing the parking brake. You could lose
braking performance which could cause an
accident. You could also wear out the brakes
prematurely.EBU18530Shift pedal This ATV is equipped with a constant-mesh 5-
speed transmission. The shift pedal is located on
the left side of the engine and is used in combina-
tion with the clutch when shifting.
1. Parking brake lever (locked position)
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EBU18720Fuel tank cap Remove the fuel tank cap by turning it counter-
clockwise.
EBU18814Fuel Make sure there is sufficient gasoline in the tank.
WARNING
EWB02521Gasoline and gasoline vapors are extremely
flammable. To avoid fires and explosions and
to reduce the risk of injury when refueling, fol-
low these instructions.1. Before refueling, turn off the engine and besure that no one is sitting on the vehicle. Nev-
er refuel while smoking, or while in the vicinity
1. Shift pedal
1
1. Fuel tank cap
1
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4
doctor immediately. If gasoline spills on your
skin, wash with soap and water. If gasoline
spills on your clothing, change your clothes.
NOTICEECB00070Use only unleaded gasoline. The use of leaded
gasoline will cause severe damage to internal
engine parts, such as the valves and piston
rings, as well as to the exhaust system.Your Yamaha engine has been designed to use
premium unleaded gasoline with a research oc-
tane number of 97 or higher. If knocking (or ping-
ing) occurs, use a gasoline of a different brand.
Use of unleaded fuel will extend spark plug life and
reduce maintenance costs.EBU18820Fuel cock The fuel cock supplies fuel from the tank to the car-
buretor while also filtering it.
The fuel cock lever positions are explained as fol-
lows and shown in the illustrations. OFF
With the fuel cock lever in this position, fuel will not
flow. Always turn the fuel cock lever to this position
when the engine is not running.
1. Arrow mark positioned over
“OFF”
1
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4-11
4ON
With the fuel cock lever in this position, fuel flows
to the carburetor. Turn the fuel cock lever to this
position when starting the engine and riding. RES
This indicates reserve. With the fuel cock lever in
this position, the fuel reserve is made available.
Turn the fuel cock lever to this position if you run
out of fuel while riding. When this occurs, refuel as
soon as possible and be sure to turn the fuel cock
lever back to
“ON ”!
EBU18840Starter (choke) Starting a cold engine requires a richer air-fuel mix-
ture, which is supplied by the starter (choke).
Move the starter (choke) in direction (a) to turn on
the starter (choke).
1. Arrow mark positioned over “ON ”
1
1. Arrow mark positioned over “RES ”
1
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4
Move the starter (choke) in direction (b) to turn off
the starter (choke).
See the “
Starting a cold engine” section on page
6-1 for proper operation.
EBU18891Seat To remove the seat
Insert your hand between the rear of the seat and
the rear fender, pull the seat lock lever upward and
pull up the seat at the rear. To install the seat
Insert the projections on the front of the seat into
the seat holders and push down on the seat at the
rear. Make sure that the seat is securely fitted.1. Starter (choke)
1(a)
(b)
1. Seat lock lever
1
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5
EBU19201
PRE-OPERATION CHECKS
EBU19224Inspect your vehicle each time you use it to make sure the vehicle is in safe operating condition. Always
follow the inspection and maintenance procedures and schedules described in the Owner’s Manual.
WARNING
EWB00481Failure to inspect or maintain the vehicle properly increases the possibility of an accident or equip-
ment damage. Do not operate the vehicle if you find any problem. If a problem cannot be corrected
by the procedures provided in this manual, have the vehicle inspected by a Yamaha dealer.Before using this vehicle, check the following points:
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 oil tank, and add recommended oil to spec-
ified 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
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EBU19541Fuel Make sure that there is sufficient fuel in the tank.
(See page 4-8.)EBU19560Engine oil Make sure that the engine oil is at the specified lev-
el. Add oil as necessary. (See page 8-14.)EBU19631Coolant Make sure that the coolant is at the specified level.
Add coolant as necessary. (See page 8-20.)TIPThe coolant level must be checked on a cold en-
gine since the level varies with engine tempera-
ture.EBU19712Front 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,
have a Yamaha dealer check the brake system.
Brake fluid level
Check the brake fluid level. Add fluid if necessary.
(See page 8-33.)
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 8-32.) Specified brake fluid:
DOT 4
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EBU19881
OPERATION
EBU19901Read the Owner’s Manual carefully before riding
the ATV. If there is a control or function you do not
understand, ask your Yamaha dealer.
WARNING
EWB00631Read the Owner ’s Manual carefully to become
familiar with all controls in order to help pre-
vent any loss of control, which could cause an
accident or injury.EBU20184Starting a cold engine NOTICEECB00150See the “Engine break-in ” section on page 6-5
prior to operating the engine for the first time.1. Set the parking brake.
2. Turn the fuel cock to “ON ”.
3. Turn the key to “ON ” and the engine stop
switch to “”. 4. Shift the transmission into neutral. The neutral
indicator light should come on. If the indicator
light does not come on, have a Yamaha deal-
er check the electrical circuit.
TIPThis model is equipped with an ignition circuit cut-
off system. The engine can be started under the
following conditions.
The transmission is in neutral.
The clutch is disengaged with the transmission
in gear. However, it is recommended to shift into
neutral before starting the engine.5. Use the starter (choke) in reference to the fig-ure:
Position (1):
Cold engine start with ambient temperature
below 5 ° C (40 °F).
Position (2):
Cold engine start with ambient temperature
between 0 ° C (30 °F) and 30 ° C (90 °F).
Position (3):
Cold engine start with ambient temperature
above 25 °C (80 °F).
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