engine YAMAHA YFZ450R 2021 Owner's Manual

7-4
7
Always use the clutch when changing gears.
The engine, transmission and drive train are
not designed to withstand the shock of
forced shifting and can be damaged by shift-
ing without using the clutch.
EBU20674Engine break-inThere is never a more important period in the life
of your engine than the first 320 km (200 mi) or 20
hours of operation. For this reason, you should fol-
low the engine break-in instructions carefully.
Since the engine is brand new, do not put an ex-
cessive load on it for the first 320 km (200 mi) or
20 hours. During this period the various parts in
the engine wear and polish themselves to the cor-
rect operating clearances. Avoid prolonged full-
throttle operation or any condition that might re-
sult in engine overheating.
0–160 km (0–100 mi) or 0–10 hours
Avoid prolonged operation above 1/2 throttle.
Vary the speed of the ATV regularly. Do not oper-
ate it at one set throttle position. 160–320 km (100–200 mi) or 10–20 hours
Avoid prolonged operation above 3/4 throttle. Rev
the engine through the gears freely, but do not use
full throttle at any time.
320 km (200 mi) or 20 hours and beyond
The ATV can now be operated normally.
NOTICEECB00221If any engine trouble should occur during the
engine break-in period, immediately have a
Yamaha dealer check the ATV. EBU26762ParkingWhen parking the ATV, shift into first gear, stop
the engine, and then apply the parking brake.
UBKD60E0.book Page 4 Wednesday, November 18, 2020 8:39 AM

7-5
7
EBU20907Parking on a slope
WARNING
EWB00852Avoid parking on hills or other inclines. Parking
on a hill or other incline could cause the ATV to
roll out of control, increasing the chance of an
accident. If you must park on an incline, place
the ATV transversely across the incline, shift
into first gear, stop the engine, apply the park-
ing brake, and then block the front and rear
wheels with rocks or other objects.Never park the ATV on hills that are too steep
to walk up easily.
1. Bring the ATV to a stop by applying the
brakes.
2. With the brake pedal applied, shift into first gear and then stop the engine.
3. Apply the parking brake.EBU20911Accessories and loadingEBU20922Genuine Yamaha Accessories
Choosing accessories for your ATV is an impor-
tant decision. Genuine Yamaha Accessories,
which are available only from a Yamaha dealer,
1. Parking brake lever (locked position)UBKD60E0.book Page 5 Wednesday, November 18, 2020 8:39 AM

8-3
8the time to learn the basic techniques well before
attempting more difficult maneuvers. Become fa-
miliar with this ATV at slow speeds first, even if you
are an experienced operator.
Not recommended for children under 16 years
of age.
WARNING
EWB01391A child under 16 should never operate an ATV
with engine size greater than 90 cc. Use by
children of ATVs that are not recommended for
their age can lead to severe injury or death of
the child.
This ATV is designed to carry the operator only
– passengers prohibited.
The long seat is to allow the operator to shift posi-
tion as needed during operation. It is not for carry-
ing passengers.
WARNING! Never carry a
passenger. Carrying a passenger on this ATV
greatly reduces your ability to balance and
control this ATV. You could have an accident,
resulting in severe injury or death to you and/or
your passenger.
[EWB01402]
UBKD60E0.book Page 3 Wednesday, November 18, 2020 8:39 AM

8-5
8Pre-operation checks
Always inspect your ATV each time you use it to
make sure the ATV is in safe operating condition.
Perform the pre-operation checks listed on page
6-1. Always follow the inspection and mainte-
nance procedures and schedules described in the
Owner’s Manual.
WARNING! Failure to inspect
the ATV before riding it or failure to maintain it
properly increases the possibility of an acci-
dent and equipment damage.
[EWB01433]
Speed limiter
For riders less experienced with this model, the
throttle lever housing is equipped with a speed
limiter. 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 decreases the maximum speed of the ATV.
Turning in the adjusting screw decreases top
speed, and turning it out increases top speed.
(See page 5-4.)
Loading and accessories
WARNING
EWB00973Improper loading or towing can increase the
risk of loss of control, an overturn, or other ac-
cident. To reduce the risk of an accident:1. Adjusting screw
2. Locknut
2
1
UBKD60E0.book Page 5 Wednesday, November 18, 2020 8:39 AM

8-7
8Avoid wheelies and jumping.
WARNING! At-
tempting wheelies, jumps, and other stunts in-
creases the chance of an accident, including
an overturn. Never attempt stunts, such as
wheelies or jumps. Don’t try to show off.
[EWB01482]Modifications and accessories
Never modify this ATV through improper installa-
tion or use of accessories or other modification. All
parts and accessories added to this ATV should
be genuine Yamaha or equivalent components
designed for use on this ATV and should be in-
stalled and used according to instructions. If you have questions, consult an authorized ATV dealer.
WARNING! Operating this ATV with improper modifications may cause changes in handling
which in some situations could lead to an acci-
dent.
[EWB01492]
Exhaust system
WARNING
EWB01502 Dry grass or brush or other combustible ma-
terial accumulated around the engine area
could catch fire. Do not operate, idle, or park
the ATV in dry grass or other dry ground cov-
er. Keep the engine area free of dry grass,
brush, or other combustible material.
 Someone touching the exhaust system dur-
ing or after operation could be burned. Do
not touch the hot exhaust system. Do not
park the ATV in a place where others might
be likely to touch it. The muffler and other engine parts become ex-
tremely hot during operation and remain hot after
the engine has stopped. To reduce the risk of fire
during operation or after leaving the ATV, do not
let brush, grass and other materials collect under
the vehicle, near the muffler or exhaust pipe, or
UBKD60E0.book Page 7 Wednesday, November 18, 2020 8:39 AM

8-11
8Select 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.
Set the parking brake and follow the instruction on
page 7-1 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. With the engine idling, pull the
clutch lever to disengage the clutch and shift into
1st gear, and then release the parking brake.
Open the throttle gradually, and at the same time,
release the clutch lever slowly. Once the ATV has
attained adequate speed, release the throttle lever
and at the same time, quickly pull in the clutch le-
ver and shift into 2nd gear. Open the throttle part
way and gradually release the clutch.
WARNING!
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 con- trol.
[EWB02632]

NOTICE: Do not shift gears without
releasing the throttle. Damage to the engine or
drive train may occur.
[ECB01072]
Use this same procedure as you move into the
higher gears. Be sure to coordinate the use of the
throttle and shift pedal properly.
Avoid higher speeds until you are thoroughly fa-
miliar with the operation of your ATV.
When slowing down or stopping, release the
throttle 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 en-
gaging a lower gear. Improper use of the brakes or
shifting can cause the tires to lose traction, reduc-
ing control and increasing the possibility of an ac-
cident.
TURNING YOUR ATV
WARNING
EWB01772Always follow proper procedures for turning as
described in this Owner’s Manual. Practice
turning at low speeds before attempting to turn
at faster speeds. Do not turn at speeds too fast
for your skills or the conditions. ATV could go
out of control, causing a collision or overturn.
UBKD60E0.book Page 11 Wednesday, November 18, 2020 8:39 AM

8-16
8
RIDING DOWNHILL
WARNING
EWB01132Going down a hill improperly could cause over-
turns or loss of control. Always follow proper
procedures for going down hills as described
in this Owner’s Manual.
 Always check the terrain carefully before you
start down any hill. 
Never operate the ATV on hills too steep for
the ATV or for your abilities. The ATV can
overturn more easily on extremely steep hills
than on level surfaces or small hills.
 Shift your weight backward and to the up
side of the hill.
 Never go down a hill at high speed.
 Avoid going down a hill at an angle that
would cause the ATV to lean sharply to one
side. Go straight down the hill where possi-
ble.
 Improper braking can cause the wheels on
the uphill side to come off the ground or
cause loss of traction. Gradually apply only
the rear brake when going downhill.
When riding your ATV downhill, shift your weight
as far to the rear and uphill side of the ATV as pos-
sible. Move back on the seat and sit with your
arms straight. Choose a low gear which will allow
the engine compression to do most of the braking
for you.
Use caution while descending a hill with loose or
slippery surfaces. Braking ability and traction may
be adversely affected by these surfaces. Improper
braking may also cause a loss of traction. Gradu-
ally apply only the rear brake.
UBKD60E0.book Page 16 Wednesday, November 18, 2020 8:39 AM

9-1
9
EBU28789
PERIODIC MAINTENANCE AND ADJUSTMENT
EBU21677Periodic inspection, adjustment, and lubrication
will keep your vehicle in the safest and most effi-
cient condition possible. Safety is an obligation of
the vehicle owner and operator. The most impor-
tant points of vehicle inspection, adjustment, and
lubrication are explained on the following pages.
WARNING
EWB01842Failure to properly maintain the vehicle or per-
forming maintenance activities incorrectly may
increase your risk of injury or death during ser-
vice or while using the vehicle. If you are not fa-
miliar with vehicle service, have a Yamaha
dealer perform the service.
WARNING
EWB02563Turn off the engine when performing mainte-
nance unless otherwise specified.
A running engine has moving parts that can
catch on body parts or clothing and electri-
cal parts that can cause shocks or fires. 
Running the engine while servicing can lead
to eye injury, burns, fire, or carbon monoxide
poisoning - possibly leading to death. See
page 3-6 for more information about carbon
monoxide.

WARNING
EWB02691Brake discs, calipers, drums, and linings can
become very hot during use. To avoid possible
burns, let brake components cool before
touching them. The intervals given in the periodic maintenance
charts should be considered as a general guide
under normal riding conditions. However, DE-
PENDING ON THE WEATHER, TERRAIN, GEO-
GRAPHICAL LOCATION, AND INDIVIDUAL USE,
THE MAINTENANCE INTERVALS MAY NEED TO
BE SHORTENED.
UBKD60E0.book Page 1 Wednesday, November 18, 2020 8:39 AM

9-3
9
EBU21748Periodic maintenance chart: Emission control systemTIPFor ATVs not equipped with an odometer or an hour meter, follow the month maintenance intervals in-
stead.
 For odometer or hour meter-equipped vehicles, follow the month maintenance interval if the ATV isn’t
ridden for the stated mileage or engine operating hours.
 Items marked with an asterisk should be performed by a Yamaha dealer as they require special tools,
data and technical skills. NO. ITEM CHECK OR MAINTENANCE
JOB INITIAL
EVERY
Whichev-
er comes first month136612
km (mi) 320
(200) 1300
(800) 2500
(1600) 2500
(1600) 5000
(3200)
hours 20 80 160 160 320
1 *Fuel line • Check fuel hoses for cracks or other damage, and
replace if necessary. √√√
• Replace. Every 5 years
2 *Spark plug • Check condition and clean, regap, or replace if
necessary. √√√√√
3 *Va l ve s • Check valve clearance and adjust if necessary. √ √√√
4 *Crankcase breath-
er system • Check breather hose for cracks or other damage,
and replace if necessary. √√√
UBKD60E0.book Page 3 Wednesday, November 18, 2020 8:39 AM

9-5
9
EBU2186EPeriodic maintenance chart: General maintenance and lubricationTIPFor ATVs not equipped with an odometer or an hour meter, follow the month maintenance intervals in-
stead.
 For odometer or hour meter-equipped vehicles, follow the month maintenance interval if the ATV isn’t
ridden for the stated mileage or engine operating hours.
 Items marked with an asterisk should be performed by a Yamaha dealer as they require special tools,
data and technical skills. NO. ITEM CHECK OR MAINTENANCE
JOB INITIAL
EVERY
Whichev-
er comes first month136612
km (mi) 320
(200) 1300
(800) 2500
(1600) 2500
(1600) 5000
(3200)
hours 20 80 160 160 320
1 Air filter element • Clean and replace if necessary. Every 20–40 hours (more often in wet or
dusty areas)
2 *Clutch • Check operation and adjust if necessary. √ √√√
3 *Front brake • Check operation and correct if necessary.
• Check fluid level and ATV for fluid leakage, and
correct if necessary. √√√√√
• Replace brake pads. Whenever worn to the limit
4 *Rear brake • Check operation and correct if necessary.
• Check fluid level and ATV for fluid leakage, and
correct if necessary. √√√√√
• Replace brake pads. Whenever worn to the limit
UBKD60E0.book Page 5 Wednesday, November 18, 2020 8:39 AM