engine YAMAHA YFZ450R 2021 Owners Manual

EBU17421
TABLE OF CONTENTS
VEHICLE IDENTIFICATION ............................ 1-1Identification numbers ................................ 1-1
LOCATION OF THE WARNING AND
SPECIFICATION LABELS .............................. 2-1
SAFETY INFORMATION ................................ 3-1
DESCRIPTION................................................ 4-1 Left view ...................................................... 4-1
Right view.................................................... 4-1
Controls and instruments............................ 4-2
INSTRUMENT AND CONTROL
FUNCTIONS ................................................... 5-1 Main switch ................................................. 5-1
Indicator light and warning lights ................ 5-1
Handlebar switches .................................... 5-3
Throttle lever ............................................... 5-4
Speed limiter ............................................... 5-4
Clutch lever ................................................. 5-5
Brake lever .................................................. 5-5
Brake pedal ................................................. 5-6
Parking brake lever ..................................... 5-6 Shift pedal................................................... 5-7
Fuel tank cap .............................................. 5-8
Fuel ............................................................. 5-9
Seat .......................................................... 5-10
Front shock absorbers ............................ 5-11
Rear shock absorber ................................ 5-15
Handlebar position ................................... 5-23
PRE-OPERATION CHECKS .......................... 6-1 Fuel ............................................................. 6-4
Engine oil .................................................... 6-4
Coolant ....................................................... 6-4
Front and rear brakes ................................. 6-4
Throttle lever ............................................... 6-5
Drive chain .................................................. 6-5
Tires ............................................................ 6-5
Chassis fasteners ....................................... 6-7
Instruments, lights and switches ................ 6-7
OPERATION .................................................. 7-1 Starting the engine ..................................... 7-1
Shifting........................................................ 7-2
Engine break-in........................................... 7-4
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Parking on a slope ...................................... 7-5
Accessories and loading ............................. 7-5
RIDING YOUR ATV ........................................ 8-1 GETTING TO KNOW YOUR ATV ................ 8-2
RIDE WITH CARE AND GOOD JUDGMENT .............................................. 8-2
BE CAREFUL WHERE YOU RIDE ............... 8-8
TURNING YOUR ATV................................ 8-11
CLIMBING UPHILL ................................... 8-13
RIDING DOWNHILL .................................. 8-16
CROSSING A SLOPE................................ 8-17
CROSSING THROUGH SHALLOW WATER .................................................... 8-18
RIDING OVER ROUGH TERRAIN ............. 8-20
SLIDING AND SKIDDING.......................... 8-20
WHAT TO DO IF... ..................................... 8-21
PERIODIC MAINTENANCE AND
ADJUSTMENT................................................ 9-1 Owner’s Manual and tool kit ....................... 9-2
Periodic maintenance chart: Emission control system .......................................... 9-3
Periodic maintenance chart: General maintenance and lubrication..................... 9-5
Removing and installing the cowling and panels...................................................... 9-10 Checking the spark plug........................... 9-13
Engine oil and oil filter element................. 9-14
Why Yamalube ......................................... 9-20
Coolant ..................................................... 9-20
Cleaning the air filter element ................... 9-22
Cleaning the spark arrester ...................... 9-26
Adjusting the throttle lever free play ......... 9-28
Valve clearance......................................... 9-28
Brakes....................................................... 9-28
Checking the front and rear brake pads... 9-29
Checking the brake fluid level .................. 9-30
Changing the brake fluid .......................... 9-31
Checking the front brake lever free play... 9-32
Checking the brake pedal height.............. 9-32
Adjusting the parking brake free play ....... 9-33
Brake light switches ................................. 9-34
Adjusting the clutch lever free play .......... 9-35
Drive chain slack....................................... 9-36
Lubricating the drive chain ....................... 9-38
Checking and lubricating the cables ........ 9-38
Checking and lubricating the brake and
clutch levers ........................................... 9-39
Checking the shift pedal ........................... 9-40
Checking and lubricating the brake pedal ....................................................... 9-40
Checking the wheel hub bearings ............ 9-40
Lubricating the swingarm pivots .............. 9-41
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EBU17432
SAFETY INFORMATION
SAFETY INFORMATION
EBU29375AN ATV IS NOT A TOY AND CAN BE HAZARD-OUS TO OPERATE.An ATV handles differently from other vehicles, in-
cluding motorcycles and cars. A collision or roll-
over can occur quickly, even during routine
maneuvers such as turning and riding on hills or
over obstacles, if you fail to take proper precau-
tions.
SEVERE INJURY OR DEATH can result if you do
not follow these instructions:
Read this manual and all labels carefully and fol-
low the operating procedures described.
 Never operate an ATV without proper training or
instruction. Take a training course. Beginners
should receive training from a certified instruc-
tor. Contact an authorized ATV dealer to find
out about the training courses nearest you.
 Always follow the age recommendation:
– A child under 16 years old should never oper-
ate an ATV with engine size greater than 90 cc. 
Never allow a child under age 16 to operate an
ATV without adult supervision, and never allow
continued use of an ATV by a child if he or she
does not have the abilities to operate it safely.
 Never carry a passenger on an ATV.
 This vehicle is intended for off-road use only. Do
not operate on any paved surfaces such as:
sidewalks, driveways, parking lots, paved
roads, public streets or other motorway.
 Watch carefully for other vehicles when operat-
ing on unpaved public streets or roads. Make
sure you know your country’s laws and regula-
tions before you ride on unpaved public streets
or roads.
 Never operate an ATV without wearing an ap-
proved motorcycle helmet that fits properly.
You should also wear eye protection (goggles
or face shield), gloves, boots, a long-sleeved
shirt or a jacket, and long pants.
 Never consume alcohol or drugs before or while
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3-4
3In the event of an accident
1. If serious injuries are incurred, you may be safer staying next to your vehicle; it may
shield you from oncoming riders. Depending
on your injuries and position in the trail; you
must make a judgment call as to whether you
should move to a position off the trail. If you
have sustained head, neck, or back injuries,
or cannot feel your limbs, you should not
move. Keep your helmet on and remain mo-
tionless. Lie down next to your vehicle and
wait for help.
2. If less serious injuries are incurred and you can walk, then move to a position off the trail.
Check yourself for injuries and apply first aid
as needed.
3. If your injuries are light, when safe to do so, move your vehicle off the trail to avoid colli-
sions with oncoming riders. Check for injuries
and apply first aid as necessary. If you can
physically operate your vehicle, inspect your
vehicle. If the vehicle is in safe operating con-
dition and you can safely operate it, restart it
and ride gently back to camp or other known
location where you can receive medical at- tention. If necessary, contact your riding party
or local authorities to let them know where
you are and what has happened.
In the event of a breakdown 1. If your vehicle will not restart or is not in safe operating condition, turn off the main switch
and engine stop switch. If the breakdown oc-
curs at twilight or night, leave the main switch
on so that your lights may warn other riders of
your stopped vehicle.
2. Get out of danger. Check for oncoming vehi- cles and when safe, push your vehicle to the
side of the trail or even off the main trail to
avoid any possible collisions with oncoming
riders. If you cannot move your vehicle by
yourself, when safe, walk to the nearest van-
tage point and signal an oncoming rider to
help you push your vehicle to a safe place off
the trail.
3. Inspect your vehicle for any immediate haz- ardous conditions. The most obvious hazard-
ous conditions are leaking fuel and
ungrounded or broken wiring. Visually check
for broken wiring and leaking fuel. Leaking
fuel can be confirmed by the odor of gasoline.
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3-5
3
4. Once immediate safety hazards are con-
firmed not to exist, you may remove your hel-
met to more closely inspect your vehicle.
Check for external signs of wear, broken
parts, fluid leaks, cracks in the frame, sus-
pension damage, wheel damage, and so on.
Fuel, oil, and coolant usually give off a notice-
able odor.
5. If your vehicle will not restart or if it is unsafe to ride, then turn off all vehicle systems (en-
gine stop switch, main switch, and fuel cock),
and then signal or go for help.
Aftermarket Parts, Accessories, and Modifica-
tions
While you may find aftermarket products similar in
design and quality to genuine Yamaha accesso-
ries, recognize that some aftermarket accessories
or modifications are not suitable because of po-
tential safety hazards to you or others. Installing
aftermarket products or having other modifica-
tions performed to your vehicle that change any of
the vehicle’s design or operation characteristics
can put you and others at greater risk of serious
injury or death. You are responsible for injuries re-
lated to changes in the vehicle. Keep the following guidelines in mind, as well as those found in the
Loading section (page 7-6) when mounting acces-
sories.

Never install accessories that would impair the
performance of your ATV. Carefully inspect the
accessory before using it to make sure that it
does not in any way reduce ground clearance,
limit suspension travel, steering travel or control
operation.
 Accessories fitted to the ATV can create insta-
bility due to improper weight distribution.
 Bulky or large accessories may seriously affect
the stability of the ATV.
 Certain accessories can displace the operator
from his or her normal riding position. This im-
proper position limits the freedom of movement
of the operator and may limit control ability,
therefore, such accessories are not recom-
mended.
 Use caution when adding electrical accesso-
ries. If electrical accessories exceed the capac-
ity of the ATV’s electrical system, an electric
failure could result, which could cause a dan-
gerous loss of lights or engine power. Also, the
battery tends to discharge more quickly if elec-
trical accessories are added.
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3-6
3
WARNING
EWB00073Avoid Carbon Monoxide Poisoning
All engine exhaust contains carbon monoxide,
a deadly gas. Breathing carbon monoxide can
cause headaches, dizziness, drowsiness, nau-
sea, confusion, and eventually death.
Carbon Monoxide is a colorless, odorless,
tasteless gas which may be present even if you
do not see or smell any engine exhaust. Deadly
levels of carbon monoxide can collect rapidly
and you can quickly be overcome and unable
to save yourself. Also, deadly levels of carbon
monoxide can linger for hours or days in en-
closed or poorly ventilated areas. If you experi-
ence any symptoms of carbon monoxide
poisoning, leave the area immediately, get
fresh air, and SEEK MEDICAL TREATMENT.
Do not run engine indoors. Even if you try to
ventilate engine exhaust with fans or open
windows and doors, carbon monoxide can
rapidly reach dangerous levels.
 Do not run engine in poorly ventilated or par-
tially enclosed areas such as barns, garages,
or carports. 
Do not run engine outdoors where engine
exhaust can be drawn into a building through
openings such as windows and doors.

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4-1
4
EBU17681
DESCRIPTION
EBU17691Left view
EBU17701Right view
1. Front shock absorber
2. Engine oil tank filler cap
3. Rear brake fluid reservoir
4. Battery
5. Shift pedal
6. Coolant reservoir
563
1
4
2
1. Spark arrester
2. Fuse
3. Fuel tank cap
4. Oil filter element
5. Brake pedal
6. Rear brake light switch
7. Rear shock absorber
456
2
1
7
3
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5-1
5
EBU17739
INSTRUMENT AND CONTROL FUNCTIONS
EBU29913Main switch“” (on)
All electrical systems are supplied with power. The
engine can be started. The key cannot be re-
moved.
“ ” (off)
All electrical systems are off. The key can be re-
moved.
EBU29383Indicator light and warning lightsEBU17861Neutral indicator light “ ”
This indicator light comes on when the transmis-
sion is in the neutral position.
1. Main switch
OFF
ON
1
1. Fuel level warning light Ž
2. Engine trouble warning light Ž
3. Coolant temperature warning light Ž
4.
12 34
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5-2
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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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5-3
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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