YAMAHA YFM90R 2009 Owners Manual

8-18
6. 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.
7. Install the sponge material onto the air filter element holder.
8. Place the air filter element in the original position, and then install the screw.
9. Install the air filter case cover by installing the bolts.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 ar-
eas. Each time the air filter element maintenance
is performed, check the air inlet of the air filter casefor obstructions.N O T I C E Make sure that the air filter element is prop-
erly seated in the air filter case.Never operate the engine with the air filter el- ement removed. This will allow unfiltered air
to enter the engine, causing rapid engine
wear and possible engine damage. Addition-
ally, operation without the air filter element
will affect carburetor jetting with subsequent
poor performance and possible engine over-
heating.
8

8-19
Cleaning the spark arrester Be sure the exhaust pipe and muffler are cool be-
fore cleaning the spark arrester.1. Remove the screw and nut. 2. Remove the spark arrester by pulling it out
of the muffler.
3. 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 screw holes.
5. Install the screw and nut, and then tighten the
nut.
1. Spark arrester
2. Screw3. Nut
8
1
2
3

8-20
Adjusting the carburetor The carburetor should be checked and, if neces-
sary, adjusted at the intervals specified in the peri-
odic maintenance and lubrication chart. The
carburetor is an important part of the engine and
requires very sophisticated adjustment. Therefore,
most carburetor adjustments should be left to a
Yamaha dealer, who has the necessary profes-
sional knowledge and experience. The adjustment
described in the following section, however, may
be performed by the owner as part of routine main-
tenance.N O T I C E The 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 ordamage to the engine. Adjusting the engine idling speed The engine idling speed must be checked and, if
necessary, adjusted as follows at the intervals
specified in the periodic maintenance and lubrica-
8
WARNING
Do not start the engine when cleaning the
spark arrester, otherwise it could cause injury
to the eyes, burns, carbon monoxide poison-
ing, possibly leading to death, and start a fire.
Always let the exhaust system cool prior totouching exhaust components.

8-21
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tion chart.TIPA diagnostic tachometer is needed to make thisadjustment.1. Start the engine and warm it up.TIPThe engine is warm when it quickly responds to thethrottle.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 theadjustment. Checking the throttle cable free play The throttle cable free play should be checked at
the intervals specified in the periodic maintenance
and lubrication chart.1. Throttle stop screwEngine idling speed:1600–1800 r/min
1
(b)
(a)

8-22
The throttle cable free play should measure 1.0–
3.0 mm (0.04–0.12 in) at the throttle lever. Period-
ically check the throttle cable free play and, if nec-
essary, have a Yamaha dealer adjust it. Timing chainThe timing chain stretches with use, resulting in im-
proper valve timing and engine noise. To prevent
this from occurring, the timing chain tensioner
must be adjusted by a Yamaha dealer at the inter-
vals specified in the periodic maintenance and lu-
brication chart.
Valve 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.
1. Throttle lever free play
1
BrakesReplacement of brake components requires
professional knowledge.Brake service should be
performed by a Yamaha dealer.
WARNING
Operating with improperly serviced or adjusted
brakes could lead to a loss
in braking ability
and an accident.
8
Checking the front brake shoesThe front brake shoes must be checked for wear at
the intervals specified in the periodic maintenance
and lubrication chart. Front brake is provided with a
wear indicator on front brake lever, which allows you

8
8-23
Adjusting the front brake lever free
playThe brake lever free play must be checked and, if
necessary, adjusted at the intervals specified in
the periodic maintenance and lubrication chart.
1
The brake lever free play should measure 4.0–
6.0 mm (0.16–0.24 in) as shown. If the free play
is incorrect, adjust it as follows.101. 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 free play, and in direction (b) to
decrease it.
1. Brake lever free play
TIPBefore adjusting the brake lever free play, checkthe front brake shoes for wear.
3
3. No more than 12 mm (0.47 in)
1. Upper adjusting bolt
2. Lower adjusting bolt
2 1
to check the brake shoe wear without having to
disassemble the brake. To check the brake shoe
wear, there are two adjusting bolts to indicate brake
shoe wear. If the positions of adjusting bolts reach to
12mm (0.47in), the brake shoes should be replaced
as a set by Yamaha dealer.

4. Tighten the lower locknut.
5. While applying the front brake, turn out the up-per adjusting bolt until the upper and lower ca-
ble lengths are equal. The cable joint will
become vertical.1. Upper locknut
2. Upper adjusting bolt
3. Lower locknut
4. Lower adjusting bolt
12
4
3 (a)(b)
(a)
(b)
11. Cable joint6. Tighten the upper locknut.
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8
WARNING
Operating with improperly serviced or adjust-
ed brakes could cause loss of braking ability,
which could lead to an accident.

8-25
The rear brake pads must be checked for wear at the
intervals specified in the periodic maintenance and
lubrication chart. Each brake pad is provided with
wear indicator grooves, which allow you to check the
brake pad wear without having to disassemble the
brake. If a brake pad has worn to the point that the
wear indicator grooves have almost disappeared,
have a Yamaha dealer replace the brake pads as a
set.Checking the rear brake pads
Insufficient brake fluid may allow air to enter the brake
system, possibly causing it to become ineffective.
Before riding, check that the brake fluid is above the
minimum level mark and replenish if necessary.
A low brake fluid level may indicate worn brake pads
and/or brake system leakage. If the brake fluid level
is low, be sure to check the brake pads for wear and
the brake system for leakage.Checking the brake fluid level 1. Wear indicator groove
8
1
After servicing:Make sure the brakes operate smoothly and
that the free play is correct.Make sure the brakes do not drag.
Replacement of brake components requires
professional knowledge. These proceduresshould be performed by a Yamaha dealer.

Changing the rear brake fluidChecking the rear brake lever free play
The brake lever free play must be checked at the
intervals specified in the periodic maintenance and
lubrication chart. The brake lever free play should
measure 0 – 1.5 mm (0 – 0.06 in) as shown. If
the free play is incorrect, have a Yamaha dealer
check the brake system.
1
LOWER
1
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8
Recommended brake fluid:
DOT4
1. Brake lever free play
1. Minimum level mark
Have a Yamaha dealer change the rear brake fluid
at the intervals specified in the TIP after the periodic
maintenance and lubrication chart. In addition,
have the oil seals of the master cylinders and
calipers as well as the brake hoses replaced at the
intervals listed below or whenever they are damaged
or leaking.
Oil seals: Replace every two years.Brake hoses: Replace every four years.

8-27
Checking and lubricating the cables The 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.
Checking and lubricating the front and
rear brake levers The 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:
Engine oil
8
WARNING
Operating with improperly serviced or adjust-
ed brakes could cause loss of braking ability,
which could lead to an accident.
After servicing:Make sure the brakes operate smoothly and
that the free play is correct.Make sure the brakes do not drag.Make sure the brakes are not spongy. All air
must be bled from the brake system.
Replacement of brake components requires
professional knowledge. These proceduresshould be performed by a Yamaha dealer.
WARNING
Inspect cables frequently and replace if dam-
aged. Corrosion can result when the cable
sheaths become damaged, and cables can
also become frayed or kinked, which could re-
strict the operation of controls and lead to anaccident or injury.