exhaust YAMAHA YFZ450R 2021 Owners Manual

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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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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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
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8-8
8
next to other hot parts. Check under the vehicle
after operating in areas where combustible mate-
rials may have collected. Do not idle or park the
vehicle in long dry grass or other dry ground cov-
er.
To prevent burns, avoid touching the exhaust sys-
tem. Park the ATV in a place where pedestrians or
children are not likely to touch it.
BE CAREFUL WHERE YOU RIDE
This ATV is designed for use on unpaved surfaces
only.
WARNING! Paved surfaces may seriously
affect handling and control of the ATV, and
may cause the ATV to go out of control. Always
avoid paved surfaces, including sidewalks,
driveways, parking lots and streets.
[EWB01512]
While riding on unpaved public streets or roads
may be legal in your area, such operation can in-
crease the risk of collision with other vehicles.
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9-4
9
5*Exhaust system • Check for leakage and replace gasket(s) if neces-
sary.
• Check for looseness and tighten all screw clamps and joints if necessary. √√√
6Spark arrester • Clean. √√√
7 *Air induction sys-
tem • Check the air cut-off valve, reed valve, and hose
for damage.
• Replace any damaged parts if necessary. √√√√√
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
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9-19
911. Install the crankcase engine oil drain bolt, the
engine oil tank drain bolt and their new gas-
ket, and then tighten the bolts to their speci-
fied torques.
12. Refill with the specified amount of the recom- mended engine oil through the engine oil tank
filler hole.
TIPBe sure to wipe off spilled oil on any parts after the
engine and exhaust system have cooled down.
NOTICEECB00301In order to prevent clutch slippage (since the
engine oil also lubricates the clutch), do not
mix any chemical additives. Do not use oils
with a diesel specification of “CD” or oils of
a higher quality than specified. In addition,
do not use oils labeled “ENERGY CONSERV-
ING II” or higher.
 Make sure that no foreign material enters the
crankcase. 13. Check the engine oil tank filler cap O-ring for
damage, and replace it if necessary.
14. Install and tighten the engine oil tank filler cap.
15. Start the engine, and then let it idle for several minutes while checking it for oil leakage. If oil
is leaking, immediately turn the engine off and
check for the cause.
16. Turn the engine off, and then check the oil level and correct it if necessary.
17. Install the engine guard by installing the bolts, and then tighten them to the specified torque.
NOTICE: Be sure to apply LOCTITE
® to the
engine guard bolts before installing them.
[ECB00372]
Tightening torques: Crankcase engine oil drain bolt:20 N·m (2.0 kgf·m, 15 lb·ft)
Engine oil tank drain bolt: 20 N·m (2.0 kgf·m, 15 lb·ft)
Recommended oil: See page 11-1.
Oil quantity: Without oil filter element replacement:1.40 L (1.48 US qt, 1.23 Imp.qt)
With oil filter element replacement: 1.45 L (1.53 US qt, 1.28 Imp.qt)
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9-26
9
17. Install the seat.
TIPThe air filter element should be cleaned every 20–
40 hours. It should be cleaned and lubricated
more often if the ATV is operated in extremely
dusty areas. Each time the air filter element main-
tenance is performed, check the air inlet of the air
filter case for obstructions. Check the air filter
case rubber joint to the throttle body and the rub-
ber joint manifold fittings for an air-tight seal.
Tighten all fittings securely to avoid the possibility
of unfiltered air entering the engine. EBU30863Cleaning the spark arresterSelect a well-ventilated area free of combustible
materials and make sure the exhaust and muffler
are cool.
WARNING
EWB02342Always let the exhaust system cool prior to
touching exhaust components.
Do not start the engine with the spark arrester
removed. Sparks or exhaust particulate can
cause eye injury, burns, or start a fire.
1. Remove the tailpipe cover by removing the
bolts.
2. Remove the retainer by removing the bolts, and then remove the tailpipe and gasket from
the muffler.1. Tailpipe cover
2. Bolt2
1 2
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10-1
10
EBU25861
CLEANING AND STORAGE
EBU25903CleaningFrequent, thorough cleaning of your ATV will not
only enhance its appearance but will improve its
general performance and extend the useful life of
many components.1. Before cleaning the ATV: a. Block off the end of the exhaust pipe toprevent water entry. A plastic bag and
strong rubber band may be used.
b. Make sure the spark plug and all filler caps are properly installed.
2. If the engine case is excessively greasy, apply degreaser with a paint brush. Do not apply
degreaser to the chain, sprockets or wheel
axles.
3. Rinse the dirt and degreaser off with a garden hose. Use only enough pressure to do the
job. WARNING! Wet brakes may have re-
duced stopping ability, increasing the
chance of an accident. Test the brakes af-
ter washing. Apply the brakes several
times at slow speeds to let friction dry out
the linings.
[EWB02312]
NOTICE: Excessive wa- ter pressure may cause water seepage
and deterioration of wheel bearings,
brakes, transmission seals and electrical
devices. Many expensive repair bills have
resulted from improper high-pressure de-
tergent applications such as those avail-
able in coin-operated car washers.
[ECB00712]
4. Once most of the dirt has been hosed off,
wash all surfaces with warm water and mild,
detergent-type soap. An old toothbrush or
bottle brush is handy for hard-to-reach plac-
es.
5. Rinse the ATV off immediately with clean wa- ter and dry all surfaces with a chamois, clean
towel or soft absorbing cloth.
6. Dry the chain and lubricate it to prevent it from rusting.
7. Clean the seat with a vinyl upholstery cleaner to keep the cover pliable and glossy.
8. Automotive type wax may be applied to all painted and chrome plated surfaces. Avoid
combination cleaner-waxes. Many contain
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