2022 YAMAHA YFM90R Owners Manual

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9
ment removed. This will allow unfiltered air
to enter the engine, causing rapid engine
wear and possible engine damage. Addi-
tionally, operation without the air filter ele-
ment will affect carburetor jetting with
subsequent poor performance and possi-
ble engine overheating.
[ECB00462]
10. 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. When servicing the air filter element,
be sure to check the air inlet of the air filter case
for obstructions.
EBU33942Cleaning the spark arresterBe sure the exhaust pipe and muffler are cool be-
fore cleaning the spark arrester.
1. Remove the tailpipe bolt and nut.
2. Remove the spark arrester by pulling it out of the muffler.1. Spark arrester
2. Tailpipe bolt
3. Nut
1
2
3
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93. Tap the spark arrester lightly, and then use a
wire brush to remove any carbon deposits.
4. Insert the spark arrester into the muffler and align the bolt hole.
5. Install the tailpipe bolt and nut, and then tight- en the nut to the specified torque.
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. EBU23942Adjusting the carburetorThe carburetor should be checked and, if neces-
sary, adjusted at the intervals specified in the pe-
riodic maintenance chart. The carburetor is an
important part of the engine and requires very so-
phisticated adjustment. Therefore, most carbure-
tor adjustments should be left to a Yamaha dealer, who has the necessary professional knowledge
and experience. The adjustment described in the
following section, however, may be performed by
the owner as part of routine maintenance.
NOTICEECB00481The carburetor has been set and extensively
tested at the Yamaha factory. Changing these
settings without sufficient technical knowl-
edge may result in poor performance of or
damage to the engine. EBU24002Adjusting the engine idling speedThe engine idling speed must be checked and, if
necessary, adjusted as follows at the intervals
specified in the periodic maintenance chart.TIPA diagnostic tachometer is needed to make this
adjustment. 1. Start the engine and warm it up.TIPThe engine is warm when it quickly responds to
the throttle.
Tightening torque:
Tailpipe nut:10 N

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9
2. Attach the tachometer to the spark plug lead.
3. Check the engine idling speed and, if neces-
sary, adjust it to specification by turning the
throttle stop screw at the carburetor. To in-
crease the engine idling speed, turn the throt-
tle stop screw in direction (a), and to decrease
it, turn the screw in direction (b).
TIPIf the specified idling speed cannot be obtained as
described above, have a Yamaha dealer make the
adjustment. EBU38470Adjusting the throttle lever free play
1. Throttle stop screwEngine idling speed:1600–1800 r/min
(a)
(b)
1
1. Rubber cover
2. Throttle lever free play adjusting nut
3. Locknut
4. Throttle lever free playThrottle lever free playW1.5

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9Periodically check the throttle lever free play and
adjust if necessary.
TIPThe engine idling speed must be checked and ad-
justed before adjusting the throttle lever free play. 1. Slide the rubber cover away from the locknut.
2. Loosen the locknut.
3. To increase the throttle lever free play, turn
the throttle lever free play adjusting nut in di-
rection (a). To decrease the throttle lever free
play, turn the adjusting nut in direction (b).
4. Tighten the locknut.
5. Slide the rubber cover to its original position.EBU24062Valve 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 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. EBU34512Checking the front and rear brake
shoesThe front and rear brake shoes must be checked
for wear at the intervals specified in the periodic
maintenance chart. Without disassembling the
brake, this can be performed by checking the po-
sition of the brake lever free play adjusting bolts or
nut.
Front brakes
To check front brake shoe wear, check the posi-
tion of the adjusting bolts. If a bolt extends more
than 12 mm (0.47 in) from its locknut, the brake
shoes need to be replaced.
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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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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
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

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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