check 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
Parking........................................................ 7-4UBKD60E0.book Page 1 Wednesday, November 18, 2020 8:39 AM

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
UBKD60E0.book Page 2 Wednesday, November 18, 2020 8:39 AM

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.
UBKD60E0.book Page 4 Wednesday, November 18, 2020 8:39 AM

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.
UBKD60E0.book Page 5 Wednesday, November 18, 2020 8:39 AM

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.
UBKD60E0.book Page 2 Wednesday, November 18, 2020 8:39 AM

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
UBKD60E0.book Page 3 Wednesday, November 18, 2020 8:39 AM

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)
UBKD60E0.book Page 4 Wednesday, November 18, 2020 8:39 AM

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
UBKD60E0.book Page 1 Wednesday, November 18, 2020 8:39 AM

6-4
6
EBU38000FuelMake sure there is sufficient gasoline in the tank
before starting off. Refuel if necessary. (See page
5-9.)EBU19561Engine oilMake sure that the engine oil is at the specified
level. Add oil as necessary. (See page 9-14.)EBU19632CoolantMake sure that the coolant is at the specified level.
Add coolant as necessary. (See page 9-20.)TIPThe coolant level must be checked on a cold en-
gine since the level varies with engine tempera-
ture. EBU19713Front and rear brakesBrake 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
9-32.) 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 sys-
tem.
Brake fluid level
Check the brake fluid level. Add fluid if necessary.
(See page 9-30.)
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. Specified brake fluid:
DOT 4UBKD60E0.book Page 4 Wednesday, November 18, 2020 8:39 AM

7-1
7
EBU19882
OPERATION
EBU19902Read 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
EWB00632Read 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. EBU29954Starting the engineNOTICEECB00151See the “Engine break-in” section on page 7-4
prior to operating the engine for the first time. 1. Set the parking brake.
2. Turn the key to “ ” (on) and the engine stopswitch to “ ”.
The following warning lights should come on
for a few seconds, then go off. 
Coolant temperature warning light
 Fuel level warning light
 Engine trouble warning light
NOTICEECB00826To avoid possible damage, do not operate the
ATV if a warning light does not work as de-
scribed above. 3. Shift the transmission into neutral. The neutral
indicator light should come on, if it does not
come on, have a Yamaha dealer 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. 4. Completely close the throttle lever and start
the engine by pushing the start switch.
UBKD60E0.book Page 1 Wednesday, November 18, 2020 8:39 AM