engine YAMAHA YFZ450R 2018 Service Manual

8-23
8
8. Wash the sponge material gently but thor-
oughly in solvent. WARNING! Always use
parts cleaning solvent. Never use low-
flash-point solvents or gasoline because
the engine could catch fire or explode.
[EWB01943]
9. Squeeze the excess solvent out of the sponge material and let it dry. NOTICE: Do
not twist the sponge material when
squeezing it.
[ECB00442]
10. Check the sponge material and replace it if damaged.
11. Apply Yamaha foam air filter oil or other qual- ity foam air filter oil to the sponge material.TIPThe sponge material should be wet but not drip-
ping. 12. Pull the sponge material over the air filter ele-ment frame.
13. Apply all-purpose grease to the air filter ele- ment seat.
1. Sponge material
2. Air filter element frame
1
2
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8-24
814. Install the washer onto the air filter element
frame, and then insert the wing bolt into the
hole in the air filter element frame. NOTICE:
Be sure to install the washer with its
curved side facing outward as shown.
[ECB00454]
15. Insert the air filter element into the air filter case, and then tighten the wing bolt.
NOTICE: Make sure that the air filter ele-
ment is properly seated in the air filter
case. Never operate the engine with the air
filter element removed. Doing so would al-
low unfiltered air to enter the engine, caus-
ing rapid engine wear and possible engine
damage. Additionally, the fuel injection
system would be affected resulting in poor
engine performance and possible over-
heating.
[ECB00763]
16. Install the air filter case cover by hooking the holders onto the air filter case.
1. Air filter element seat
1
1. Washer
1
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8
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. EBU30862Cleaning the spark arresterSelect a well-ventilated area free of combustible
materials and make sure the exhaust and muffler
are cool.
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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8
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.
EBU29704Adjusting the throttle lever free playPeriodically check the throttle lever free play and
adjust if necessary.1. Slide the rubber cover back.
2. Loosen the locknut.
Tightening torque:
Tailpipe cover bolt:8 N·m (0.8 kgf·m, 5.9 lb·ft)1. Rubber cover
2. Throttle lever free play adjusting bolt
3. Locknut
4. Throttle lever free playThrottle lever free play: 2.0–4.0 mm (0.08–0.16 in)
32
4
(a)(b)
1
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83. To increase the throttle lever free play, turn
the throttle lever free play adjusting bolt in di-
rection (a). To decrease the throttle lever free
play, turn the adjusting bolt in direction (b).
4. Tighten the locknut.
5. Slide the rubber cover to its original position.
EBU24061Valve clearanceThe valve clearance changes with use, resulting in
improper air-fuel mixture and/or engine noise. To
prevent this from occurring, the valve clearance
must be adjusted by a Yamaha dealer at the inter-
vals specified in the periodic maintenance and lu-
brication chart.EBU29602BrakesReplacement of brake components requires pro-
fessional knowledge. Brake service should be
performed by a Yamaha dealer.
WARNING
EWB02572Operating with improperly serviced or adjust-
ed brakes could lead to a loss in braking ability
and an accident.
EBU24131Checking the front and rear brake padsThe front and rear brake pads must be checked
for wear at the intervals specified in the periodic
maintenance and lubrication chart.EBU29561Front brake pads
Each brake pad is provided with wear indicator
grooves, which allow you to check the brake pad
wear without having to disassemble the brake. To
check the brake pad wear, check the wear indica-
tor grooves. If a brake pad has worn to the point
that the wear indicator grooves have almost dis-
appeared, have a Yamaha dealer replace the
brake pads as a set.
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83. If the drive chain slack is incorrect, adjust it as
follows.
To adjust the drive chain slack 1. Place the ATV on a level surface.
2. Loosen the rear wheel axle pinch bolts.
3. Insert a rod of a diameter of 8 mm (0.3 in) and a length of 10 cm (4 in) into one of the holes in
the drive chain tensioner as shown.
TIPA rod can be obtained at a Yamaha dealer to make
this adjustment. 4. Shift the transmission into neutral.
5. To tighten the drive chain, push the ATVbackward. To loosen the drive chain, push
the ATV forward. NOTICE: Improper drive
chain slack will overload the engine as well
as other vital parts of the ATV and can lead
to drive chain slippage or breakage. To
1. Drive chain slack
1
1. Rear wheel axle pinch bolt
2. Rod
3. Drive chain tensioner
4. Hole
3
4
2 11
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82. Wipe the drive chain dry.
3. Thoroughly lubricate the drive chain with a
special O-ring chain lubricant. NOTICE: Do
not use engine oil or any other lubricants
for the drive chain, as they may contain
substances that could damage the O-
rings.
[ECB00582]
EBU24905
Checking and lubricating the cablesThe operation and the condition of all control ca-
bles should be checked before each ride, and the
cables and cable ends should be lubricated if nec- essary. If a cable is damaged or does not move
smoothly, have a Yamaha dealer check or replace
it.
WARNING
EWB02582
Inspect cables frequently and replace if
damaged. Corrosion can result when the ca-
ble sheaths become damaged, and cables
can also become frayed or kinked, which
could restrict the operation of controls and
lead to an accident or injury.
 Always make sure all control cables work
smoothly before you begin riding in cold
weather. If the control cables are frozen or
do not work smoothly, you could be unable
to control the ATV, which could lead to an
accident or collision.
1. O-rings
1
1
Recommended lubricant:
Yamaha cable lubricant or other suitable cable lubricant
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8
EBU27695Troubleshooting chartsStarting problems or poor engine performance
Check the fuel level in
the fuel tank.1. Fuel
There is enough fuel.There is no fuel.
Check the battery.
Supply fuel.
The engine does not start.
Check the battery.
Operate the electric starter.4. Compression
There is compression.
There is no compression.
The engine does not start.
Have a Yamaha dealer check the ATV.
Remove the spark plug
and check the electrodes.3. Ignition
Wipe off with a dry cloth and correct the
spark plug gap, or replace the spark plug. Have a Yamaha dealer check the ATV.
The engine does not start.
Check the compression.
DryWet
Operate the electric starter.
Have a Yamaha dealer check the ATV.
The engine does not start.
Check the ignition.
Operate the electric starter.2. Battery
The engine turns over
quickly.
The engine turns over
slowly.
The battery is good.Check the battery lead connections,
and have a Yamaha dealer charge
the battery if necessary.
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8-52
8Engine overheating
WARNING
EWB02291Wait for the engine and radiator to cool before removing the radiator cap. You could be burned by
hot fluid and steam blown out under pressure. Always put a thick rag over the cap when opening.
Allow any remaining pressure to escape before completely removing the cap. TIPIf coolant is not available, tap water can be temporarily used instead, provided that it is changed to the
recommended coolant as soon as possible. Wait until the
engine has cooled.
Check the coolant level in the
reservoir and radiator.
The coolant level
is OK.The coolant level is low.
Check the cooling system
for leakage.
Have a Yamaha dealer check
and repair the cooling system.Add coolant. (See TIP.)
Start the engine. If the engine overheats again, have a
Yamaha dealer check and repair the cooling system.
There is
leakage.
There is
no leakage.
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9
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 pla-
ces.
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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