YAMAHA YFM90R 2021 Owners Manual

9-22
9
Rear brake
To check rear brake shoe wear, check the position
of the adjusting nut. If the nut is more than 18 mm
(0.71 in) from the end of the bolt, the brake shoes
need to be replaced.
1. Upper adjusting bolt
2. Lower adjusting bolt
3. No more than 12 mm (0.47 in)
3
2 1
1. Rear brake lever free play adjusting nut
2. Bolt
3. No more than 18 mm (0.71 in)
12
3
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9
EBU24334Adjusting the front brake lever free
playPeriodically check the front brake lever free play
and adjust if necessary.1. Loosen the upper locknut and fully turn in the upper adjusting bolt.
2. Loosen the lower locknut.
3. Turn the lower adjusting bolt in direction (a) to increase the lever free play, and in direction
(b) to decrease it. 4. Tighten the lower locknut.
5. While applying the front brake, turn out the
upper adjusting bolt until the upper and lower
cable lengths are equal. The cable joint will
become vertical.1. Front brake lever free playFront brake lever free play:20.0–25.0 mm (0.79–0.98 in)
1
1. Upper locknut
2. Upper adjusting bolt
3. Lower locknut
4. Lower adjusting bolt
1 2
4
3 (a)
(b)
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9-24
9
6. Tighten the upper locknut.
TIPAfter adjusting the brake lever free play, check the
front brake shoes for wear.
EBU33784Adjusting the rear brake lever free playPeriodically check the rear brake lever free play
and adjust if necessary.
Turn the adjusting nut in direction (a) to increase
the brake lever free play, and in direction (b) to de-
crease it.
1. Cable joint1
aa´
a=a´
1. Rear brake lever free playRear brake lever free playW
30.0

9-25
9
TIPAfter adjusting the brake lever free play, check the
rear brake shoes for wear. EBU34014Drive chain slackThe drive chain slack should be checked before
each ride and adjusted if necessary.TIPWhen checking and adjusting the drive chain
slack, there should be no weight on the ATV and
all tires must be touching the ground.
To check the drive chain slack1. Place the ATV on a level surface.
2. Move the ATV back and forth to locate the tightest portion of the drive chain, and then
measure the drive chain slack as shown.
3. If the drive chain slack is incorrect, adjust it as follows.
To adjust the drive chain slack 1. Loosen the bolts and nuts.
1. Rear brake lever free play adjusting nut
1
(a)
(b)
Drive chain slack: 24.0

9-26
9
2. Loosen the rear brake lever free play adjust- ing nut. 3. Loosen the locknut.
1. Bolt
1. Nut
1
1
1. Rear brake lever free play adjusting nut
1. Drive chain slack adjusting nut
2. Locknut
1
1
2
(a)
(b)
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9-27
94. To tighten the drive chain, turn the drive chain
slack adjusting nut in direction (a). To loosen
the drive chain, turn the adjusting nut in direc-
tion (b) and push the rear wheels 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 prevent
this from occurring, keep the drive chain
slack within the specified limits.
[ECB00543]
5. Tighten the locknut, and then the bolts and nuts to their specified torques.
6. Adjust the rear brake lever free play. (See page 9-24.)
EBU24885Lubricating the drive chainThe drive chain must be cleaned and lubricated at
the intervals specified in the periodic maintenance
chart, otherwise it will quickly wear out, especially
when riding in dusty or wet areas. Service the
drive chain as follows.NOTICEECB00562The drive chain must be lubricated after wash-
ing the ATV or riding in the rain or wet areas.
Tightening torques:Locknut:22 N·m (2.2 kgf·m, 16 lb·ft)
Bolt: 45 N·m (4.5 kgf·m, 33 lb·ft)
Nut: 54 N·m (5.4 kgf·m, 40 lb·ft)
1. O-ring
1
1
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9-28
9
1. Clean the drive chain with kerosene and a
small soft brush. NOTICE: To prevent dam-
aging the O-rings, do not clean the drive
chain with steam cleaners, high-pressure
washers or inappropriate solvents.
[ECB00572]
2. 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. EBU28703Checking and lubricating the front and
rear brake leversThe operation of the front and rear brake levers
should be checked before each ride, and the lever
pivots should be lubricated if necessary.
Recommended lubricant: Yamaha cable lubricant or other suitable cable lubricantRecommended lubricant: Lithium-soap-based grease
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9-29
9Front brake lever
Rear brake lever
EBU24965Checking the wheel hub bearingsThe front and rear wheel hub bearings must be
checked at the intervals specified in the periodic
maintenance chart. If there is play in a wheel hub
or if a wheel does not turn smoothly, have a
Yamaha dealer check the wheel hub bearings.EBU36392Lubricating the front arm pivotsThe front arm pivots must be lubricated at the in-
tervals specified in the periodic maintenance
chart.Recommended lubricant: Lithium-soap-based grease
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9
TIPFor parts equipped with a grease nipple, use a
grease gun. EBU28826Lubricating the front knuckle pivotsThe front knuckle pivots must be lubricated at the
intervals specified in the periodic maintenance
chart.
TIPFor parts equipped with a grease nipple, use a
grease gun. EBU25096Lubricating the steering shaftThe steering shaft must be lubricated by a
Yamaha dealer at the intervals specified in the pe- riodic maintenance chart.
1. Grease nippleRecommended lubricant: Lithium-soap-based grease
1
1
1. Grease nippleRecommended lubricant:Lithium-soap-based grease
1
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9
TIPFor parts equipped with a grease nipple, use a
grease gun. EBU34022BatteryThis model is equipped with a 12-volt VRLA
(valve-regulated lead-acid) battery. There is no
need to check the electrolyte or to add distilled
water. However, the battery lead connections
need to be checked and tightened, and the bat-
tery terminals cleaned if corroded. If the battery
seems to have discharged, recharge it as soon as
possible.TIPWear gloves and eye protection in a ventilated
area away from sparks and open flames. Wash
hands after handling.
 It is recommended to have the battery serviced
by a Yamaha dealer.
WARNING
EWB02161Battery electrolyte is poisonous and danger-
ous, as it contains sulfuric acid, which can cau-
se severe burns. Avoid contact with skin, eyes
or clothing. Always shield your eyes when
working near batteries.
Antidote:
EXTERNAL: Flush with water.
INTERNAL: Drink large quantities of water or
milk. Follow with milk of magnesia, beaten egg
or vegetable oil. Call a physician immediately.
EYES: Flush with water for 15 minutes and get
prompt medical attention.
Batteries produce explosive gases. Keep
sparks, flame, cigarettes or other sources of
ignition away. Ventilate when charging or using
in an enclosed space.
KEEP OUT OF REACH OF CHILDREN. To remove the battery
1. Remove the seat. (See page 5-13.)
2. Unhook the battery band.
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