2021 YAMAHA YFZ450R engine

5-2
5
EBU29924Coolant temperature warning light “ ”
This warning light comes on when the engine
overheats. When this occurs, stop the engine as
soon as it is safe to do so and allow it to cool for
10 minutes.
The electrical circuit of the warning light can be
checked by turning the key to “ ” (on). The
warning light should come on for a few seconds,
and then go off.
If the warning light does not come on initially when
the key is turned to “ ” (on), or if the warning
light remains on, have a Yamaha dealer check the
vehicle.TIPThe radiator fan is automatically switched on or
off according to the coolant temperature in the
radiator.
 If the engine overheats, see page 9-53 for fur-
ther instructions. NOTICEECB00011The engine may overheat if the ATV is over-
loaded. In this case, reduce the load to spec-
ification. 
Start the engine after making sure that the
warning light is out. Continuous use while
the warning light is on may cause damage to
the engine.
EBU29933Fuel level warning light “ ”
This warning light comes on when the fuel level
drops below approximately 3.4 L (0.90 US gal,
0.75 Imp.gal). When this occurs, refuel as soon as
possible.
The electrical circuit of the warning light can be
checked by setting the engine stop switch to “ ”
and turning the key to “ ” (on). The warning light
should come on for a few seconds, and then go
off.
If the warning light does not come on initially when
the key is turned to “ ” (on), or if the warning
light remains on, have a Yamaha dealer check the
electrical circuit.EBU29944Engine trouble warning light “ ”
This warning light comes on or flashes when an
electrical circuit monitoring the engine is not work-
ing correctly. When this occurs, have a Yamaha
dealer check the self-diagnostic system.
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5
The electrical circuit of the warning light can be
checked by turning the key to “ ” (on). The
warning light should come on for a few seconds,
and then go off.
If the warning light does not come on initially when
the key is turned to “ ” (on), or if the warning
light remains on, have a Yamaha dealer check the
electrical circuit.
EBU18068Handlebar switches
EBU18081Engine stop switch “ / ”
Set this switch to “ ” before starting the engine.
The engine stop switch controls the ignition and
stops the engine when it is running. Use this
switch to stop the engine in an emergency situa-
tion. The engine will not start or run when this
switch is set to “ ”.EBU18102Start switch “ ”
Push this switch to crank the engine with the start-
er. See the starting instructions on page 7-1 prior
to starting the engine.EBU18157Light switch “ / /OFF”
Set this switch to “ ” to turn on the low beams
and the taillight. Set the switch to “ ” to turn on
the high beams and the taillight. Set the switch to
“OFF” to turn off all the lights.NOTICEECB00046Do not use the headlights with the engine
turned off for an extended period of time. The
battery may discharge to the point that the
1. Light switch “ / /OFF”
2. Engine stop switch “ / ”
3. Start switch “ ”
1
23
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5-4
5starter will not have enough power to crank the
engine. If this should happen, remove the bat-
tery and recharge it. (See page 9-43.)
EBU18286Throttle leverPush the throttle lever to increase engine speed.
Spring tension returns the lever to the rest position
when released. Always check that the throttle le-
ver returns normally before starting the engine.
EBU18325Speed limiterThe speed limiter keeps the throttle from fully
opening, even when the throttle lever is pushed to
the maximum.
Adjusting the speed limiter1. Loosen the locknut.
2. To increase the maximum engine power
available and the maximum speed of the ATV,
turn the adjusting screw in direction (a). To
decrease the maximum engine power avail-
able and the maximum speed of the ATV, turn
1. Throttle lever
1
1. Locknut
2. Adjusting screw
3. No more than 12 mm (0.47 in)
3
12
(a)
(b)
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5-6
5The brake lever is located on the right side of the
handlebar. To apply the front brake, pull the brake
lever toward the handlebar grip.
The brake lever is equipped with a position adjust-
ing bolt. To adjust the distance between the brake
lever and the handlebar grip, hold the brake lever
away from the handlebar so it does not contact
the adjusting bolt, loosen the locknut, turn the ad-
justing bolt, and then tighten the locknut.
EBU18434Brake pedal
The brake pedal is located on the right side of the
ATV. To apply the rear brake, push down on the
brake pedal.EBU18521Parking brake leverUse 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 pedal
1
1. Parking brake lever (locked position)
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5-7
5
WARNING
EWB00221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.
EBU18532Shift pedalThe shift pedal is located on the left side of the en-
gine and is used in combination with the clutch
when shifting. (See page 7-2.)
1. Parking brake lever (unlocked position)
1. Shift pedal
1
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5-8
5
EBU37980Fuel tank capRemove the fuel tank cap by turning it counter-
clockwise.
WARNING
EWB02522Gasoline 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 of sparks, open flames, or other sources of
ignition such as the pilot lights of water heat-
ers and clothes dryers.
2. Do not overfill the fuel tank. When refueling, be sure to insert the pump nozzle into the fuel
tank filler hole. Stop filling when the fuel
reaches the bottom of the filler tube. Because
fuel expands when it heats up, heat from the
engine or the sun can cause fuel to spill out of
the fuel tank.1. Fuel tank cap
1
1. Maximum fuel level
2. Fuel tank filler tube
2
1
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5-10
5About the recommended fuel
Use RON 97 octane or higher. If knocking or ping-
ing occurs, try a different brand or higher octane
gasoline. Gasoline containing ethanol can be used
if the ethanol content does not exceed 10% (E10).
Gasoline containing methanol is not recommend-
ed because it can cause damage to the fuel sys-
tem or vehicle performance problems.
NOTICEECB00071Use 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.
EBU26734SeatTo remove the seat
Insert your hand between the rear of the seat and
the rear fender, pull the seat lock lever and pull up
the seat at the rear.1. Seat lock lever
1
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6-1
6
EBU19203
PRE-OPERATION CHECKS
EBU19227Inspect 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
EWB00482Failure 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:
ITEMROUTINE PAGE
Fuel • Check fuel level in fuel tank,
and add recommended fuel if neces-
sary.
• Check fuel line for leakage. Correct if necessary. 5-9, 6-4
Engine oil • Check oil level in engine oil
tank, and add recommended oil to
specified level if necessary.
• Check ATV for oil leakage. Correct if necessary. 6-4, 9-14
Coolant • Check coolant level in reservoir, and add recommended coolant to
specified level if necessary.
• Check cooling system for leakage. Correct if necessary. 6-4, 9-20
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