2009 YAMAHA YFM90R check engine

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
8
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

8-27
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.

8-35
Troubleshooting chart
Check the fuel level in
the fuel tank.1. Fuel
There is enough fuel.There is no fuel.
Check the compression.
Supply fuel.
The engine does not start.
Check the compression.
Operate the electric starter.2. Compression
There is compression.
There is no compression.
Check the ignition. 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.
Have a Yamaha dealer
check the ATV.
The engine does not start.
Check the battery.
Operate the electric starter.4. Battery
The engine turns over
quickly.
The engine turns over
slowly.
The battery is good.Check the battery lead connections, and
charge the battery if necessary.
DryWet
Open the throttle halfway and operate
the electric starter.
8

9-3
plug, and then place the spark plug on the
cylinder head so that the electrodes are
grounded. (This will limit sparking during
the next step.)
d. Turn the engine over several times with the starter. (This will coat the cylinder wall
with oil.)
e. Remove the spark plug cap from the spark plug, and then install the spark plug and
the spark plug cap.
6. Lubricate all control cables and the pivoting points of all levers and pedals.
7. Check and, if necessary, correct the tire air pressure, and then block up the ATV so that
all of its wheels are off the ground. Alternative-
ly, turn the wheels a little every month in order
to prevent the tires from becoming degraded
in one spot.
8. Cover the muffler outlet with a plastic bag to prevent moisture from entering it.
9. Remove the battery and fully charge it. Store it in a cool, dry place and charge it once a
month. Do not store the battery in an exces-
sively cold or warm place [less than 0 °C (30
°F) or more than 30 °C (90 °F)]. For more infor-
mation on storing the battery, see page 8-26.
TIPMake any necessary repairs before storing theATV.
9

INDEX
AAccessories and loading ................................................ 6-6
Air filter element, cleaning ............................................ 8-15BBattery ........................................................................\
...8-28
Brake lever, front.............................................................4-6Brake lever, rear............................................................4-6
Brake lever free play, checking the rear........................8-26
Brake levers, checking and lubricating .............. .......... 8-27
Brakes, front and rear....................................................5-3
Brake pads, checking the rear.......................................8-25
Brake fluid level, checking the rear...............................8-25
Brake fluid level, changing the rear..............................8-26 Brake lever free play, adjusting the front......................8-23CCables, checking and lubricating ................................. 8-27
Carburetor, adjusting.................................................... 8-20
Chassis fasteners........................................................... 5-7
Cleaning..........................................................................9-1EEngine break-in .............................................................. 6-4
Engine, cold start...........................................................6-1
Engine idling speed ...................................................... 8-20 Engine oil............................................................5-3, 8-11
Engine, starting a warm................................................6-3
Engine stop switch.......................................................4-2
Fuel........................................................................4-8, 5-3
Fuel cock......................................................................4-10
Fuel tank cap..................................................................4-8
Fuse, replacing.............................................................8-30
F
KKey identification number ............................................. 11-1LLabel locations...............................................................2-1HHandlebar switches ........................................................ 4-2IIdentification numbers .................................................. 11-1
Instruments and switches.............................................5-7MMain switch .................................................................... 4-1
Maintenance and lubrication chart.................................8-5
Maintenance chart, emission control system.................8-3
Model label...................................................................11-2
Choke ............................................................................ 4-11 Brake shoes, checking the front .................................. 8-22
Final transmission oil ........................................... 5-3, 8-14
Engine speed limiter plate............................................ 4-5
Kick starter ................................................................. 4-12