2018 YAMAHA YFM90 maintenance

EBU17171
INTRODUCTION
EBU34060Congratulations on your purchase of the Yamaha YFM09RYXJ. This ATV represents the result of many
years of Yamaha experience in the production of fine sporting, touring, and pacesetting racing machines.
With the purchase of this Yamaha, you can now appreciate the high degree of craftsmanship and reliability
that have made Yamaha a leader in these fields.
This manual will provide you with a good basic understanding of the features and operation of this ATV.
This manual includes important safety information. It provides information about special techni-
ques and skills necessary to ride the ATV. It also includes basic maintenance and inspection proce-
dures. If you have any questions regarding the operation or maintenance of your ATV, please consult a
Yamaha dealer.
AN IMPORTANT SAFETY MESSAGE:
 Read this manual completely before operating your ATV. Make sure you understand all instructions.
 Pay close attention to the warning and notice labels on the ATV.
 This ATV should not be operated by a child under 10 years of age.
AN IMPORTANT NOTE TO PARENTS:
This ATV is not a toy. Before you let your child ride this ATV, you should understand the instructions and
warnings in this Owner’s Manual. Then be sure your child understands and will follow them. Children differ
in skills, physical abilities and judgment. Some children may not be able to operate an ATV safely. Parents
should supervise their child’s use of the ATV at all times. Parents should permit continued use only if they
determine that the child has the ability to operate the ATV safely.UBD362E0.book Page 1 Tuesday, January 31, 2017 5:10 PM

Parking ........................................................ 6-5
Parking on a slope ...................................... 6-5
Accessories and loading ............................. 6-6
RIDING YOUR ATV ........................................ 7-1 GETTING TO KNOW YOUR ATV ................ 7-2
RIDE WITH CARE AND GOOD JUDGMENT .............................................. 7-2
BE CAREFUL WHERE YOU RIDE ............... 7-9
TURNING YOUR ATV................................ 7-12
CLIMBING UPHILL ................................... 7-13
RIDING DOWNHILL .................................. 7-16
CROSSING A SLOPE................................ 7-17
CROSSING THROUGH SHALLOW WATER .................................................... 7-18
RIDING OVER ROUGH TERRAIN ............. 7-20
SLIDING AND SKIDDING .......................... 7-20
WHAT TO DO IF... ..................................... 7-21
WHAT TO DO... ......................................... 7-22
PERIODIC MAINTENANCE AND
ADJUSTMENT................................................ 8-1 Owner’s manual and tool kit ....................... 8-2
Periodic maintenance chart for the emission control system ........................... 8-3
General maintenance and lubrication chart .......................................................... 8-5 Checking the spark plug............................. 8-9
Engine oil .................................................. 8-11
Transmission oil ........................................ 8-14
Cleaning the air filter element ................... 8-15
Cleaning the spark arrester ...................... 8-18
Adjusting the carburetor ........................... 8-19
Adjusting the engine idling speed ............ 8-19
Adjusting the throttle lever free play ......... 8-20
Valve clearance......................................... 8-21
Brakes....................................................... 8-21
Checking the front and rear brake
shoes ...................................................... 8-21
Adjusting the front brake lever free play... 8-22
Adjusting the rear brake lever free play .... 8-24
Drive chain slack....................................... 8-25
Lubricating the drive chain ....................... 8-27
Checking and lubricating the cables ........ 8-28
Checking and lubricating the front and rear brake levers ..................................... 8-29
Checking the wheel hub bearings ............ 8-29
Lubricating the front knuckle pivots ......... 8-30
Lubricating the steering shaft ................... 8-30
Battery ...................................................... 8-31
Replacing the fuse .................................... 8-34
Removing a wheel .................................... 8-34
Installing a wheel ...................................... 8-35
Troubleshooting........................................ 8-36
UBD362E0.book Page 2 Tuesday, January 31, 2017 5:10 PM

2-2
2

Never operate at speeds too fast for your skills
or the riding conditions. Always go at a speed
that is proper for the terrain, visibility, operating
conditions, and your experience.
 Never attempt wheelies, jumps, or other stunts.
 Always inspect your ATV each time you use it to
make sure it is in safe operating condition. Al-
ways follow the inspection and maintenance
procedures and schedules described in this
manual.
 Always keep both hands on the handlebars and
both feet on the footrests of the ATV during op-
eration.
 Always go slowly and be extra careful when op-
erating on unfamiliar terrain. Always be alert to
changing terrain conditions when operating the
ATV.
 Never operate on excessively rough, slippery or
loose terrain until you have learned and prac-
ticed the skills necessary to control the ATV on
such terrain. Always be especially cautious on
these kinds of terrain.
 Always follow proper procedures for turning as
described in this manual. Practice turning at low
speeds before attempting to turn at faster
speeds and never turn at excessive speeds. 
Never operate the ATV on hills too steep for the
ATV or for your abilities. Practice on smaller hills
before attempting larger hills.
 Always follow proper procedures for climbing
hills as described in this manual. Check the ter-
rain carefully before you start up any hill. Never
climb hills with excessively slippery or loose
surfaces. Shift your weight forward. Never open
the throttle suddenly or make sudden gear
changes. Never go over the top of a hill at high
speed.
 Always follow proper procedures for going
down hills and for braking on hills as described
in this manual. Check the terrain carefully before
you start down any hill. Shift your weight back-
ward. Never go down a hill at high speed. Avoid
going down a hill at an angle that would cause
the vehicle to lean sharply to one side. Go
straight down the hill where possible.
 Always follow proper procedures for crossing
the side of a hill as described in this manual.
Avoid hills with excessively slippery or loose
surfaces. Shift your weight to the uphill side of
the ATV. Never attempt to turn the ATV around
on any hill until you have mastered the turning
UBD362E0.book Page 2 Tuesday, January 31, 2017 5:10 PM

2-4
2

Never maintain an ATV without proper knowl-
edge. Contact an authorized ATV dealer to in-
form you on basic ATV maintenance. Certain
maintenance can only be carried out by certified
staff.
In the event of an accident 1. If serious injuries are incurred, you may be safer staying next to your vehicle; it may
shield you from oncoming riders. Depending
on your injuries and position in the trail; you
must make a judgment call as to whether you
should move to a position off the trail. If you
have sustained head, neck, or back injuries,
or cannot feel your limbs, you should not
move. Keep your helmet on and remain mo-
tionless. Lie down next to your vehicle and
wait for help.
2. If less serious injuries are incurred and you can walk, then move to a position off the trail.
Check yourself for injuries and apply first aid
as needed.
3. If your injuries are light, when safe to do so, move your vehicle off the trail to avoid colli-
sions with oncoming riders. Check for injuries
and apply first aid as necessary. If you can
physically operate your vehicle, inspect your vehicle. If the vehicle is in safe operating con-
dition and you can safely operate it, restart it
and ride gently back to camp or other known
location where you can receive medical at-
tention. If necessary, contact your riding party
or local authorities to let them know where
you are and what has happened.
In the event of a breakdown 1. If your vehicle will not restart or is not in safe operating condition, turn off the main switch
and engine stop switch. If the breakdown oc-
curs at twilight or night, leave the main switch
on so that your lights may warn other riders of
your stopped vehicle.
2. Get out of danger. Check for oncoming vehi- cles and when safe, push your vehicle to the
side of the trail or even off the main trail to
avoid any possible collisions with oncoming
riders. If you cannot move your vehicle by
yourself, when safe, walk to the nearest van-
tage point and signal an oncoming rider to
help you push your vehicle to a safe place off
the trail.
3. Inspect your vehicle for any immediate haz- ardous conditions. The most obvious hazard-
ous conditions are leaking fuel and
UBD362E0.book Page 4 Tuesday, January 31, 2017 5:10 PM

4-10
43. Wipe up any spilled fuel immediately.
NOTICE: Immediately wipe off spilled fuel
with a clean, dry, soft cloth, since fuel may
deteriorate painted surfaces or plastic
parts.
[ECB00982]
4. Turn the fuel tank cap fully clockwise to make sure it is securely closed.
WARNING
EWB02532Gasoline is poisonous and can cause injury or
death. Handle gasoline with care. Never siphon
gasoline by mouth. If you should swallow some
gasoline or inhale a lot of gasoline vapor, or get
some gasoline in your eyes, see your doctor
immediately. If gasoline spills on your skin,
wash with soap and water. If gasoline spills on
your clothing, change your clothes. NOTICEECB00071Use only unleaded gasoline. The use of leaded
gasoline will cause severe damage to internal
engine parts, such as the valves and piston
rings, as well as to the exhaust system.
Your Yamaha engine has been designed to use
regular unleaded gasoline with a research octane
number of 91 or higher (95 or higher for Europe). If
knocking (or pinging) occurs, use a gasoline of a
different brand. Use of unleaded fuel will extend
spark plug life and reduce maintenance costs.EBU18821Fuel cockThe fuel cock supplies fuel from the tank to the
carburetor while also filtering it.
The fuel cock lever positions are explained as fol-
lows and shown in the illustrations.
OFF1. Arrow mark positioned over “OFF”
1
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5-1
5
EBU19203
PRE-OPERATION CHECKS
EBU19226Inspect your vehicle each time you use it to make sure the vehicle is in safe operating condition. Always
follow the inspection and maintenance procedures and schedules described in the Owner’s Manual.
WARNING
EWB00482Failure to inspect or maintain the vehicle properly increases the possibility of an accident or equip-
ment damage. Do not operate the vehicle if you find any problem. If a problem cannot be corrected
by the procedures provided in this manual, have the vehicle inspected by a Yamaha dealer. Before using this vehicle, check the following points:
ITEMROUTINE PAGE
Fuel • Check fuel level in fuel tank,
and add recommended fuel if neces-
sary.
• Check fuel line for leakage. Correct if necessary. 4-8, 5-3
Engine oil • Check oil level in engine, and add recommended oil to specified
level if necessary.
• Check ATV for oil leakage. Correct if necessary. 5-3, 8-11
Transmission oil • Check ATV for oil leakage. Correct if necessary. 5-3, 8-14
Front brake • Check operation, and correct if necessary.
• Lubricate cable if necessary.
• Check lever free play, and adjust if necessary. 5-3, 8-21, 8-22
Rear brake • Check operation, and correct if necessary.
• Lubricate cable if necessary.
• Check lever free play, and adjust if necessary. 5-3, 8-21, 8-24
UBD362E0.book Page 1 Tuesday, January 31, 2017 5:10 PM

7-5
7Pre-operation checks
Always inspect your ATV before use to make sure
that it is safe operating condition. Perform the pre-
operation checks listed on page 5-1. Follow the
maintenance schedules and procedures as de-
scribed in the “Periodic Maintenance and Adjust-
ment” section of this manual.
WARNING! Failure
to inspect the ATV before riding it or failure to
maintain it properly increases the possibility of
an accident and equipment damage.
[EWB01433]
Speed limiter
For beginning riders, riders less experienced with
this model, or whenever limited speed is desir-
able, the throttle lever housing is equipped with a vehicle speed limiter. The speed limiter keeps the
throttle from fully opening, even when the throttle
lever is pushed to the maximum. Turning in the
adjusting screw limits the maximum engine power
available and decreases the maximum speed of
the ATV. Turning in the adjusting screw decreases
top speed, and turning it out increases top speed.
(See page 4-3.)
This model also has an engine speed limiter plate
to limit the amount of engine power available.
Yamaha recommends that all beginning riders start off with the engine speed limiter plate in-
stalled and the vehicle speed limiter adjusting
screw turned in to limit the amount of speed avail-
able while they learn. The vehicle speed limiter
may be gradually adjusted to increase maximum
speed as the beginner becomes more familiar with
operating the ATV. Parents should decide when to
adjust the ATV for more power as their young-
ster’s riding skills improve. Once the ATV rider can
operate with skill at the top speed permitted by
adjusting the vehicle speed limiter alone, the en-
gine speed limiter plate can be removed. Since re-
moval of this plate will result in a significant
increase in power, turn the vehicle speed limiter
adjusting screw back in again and adjust it out inUBD362E0.book Page 5 Tuesday, January 31, 2017 5:10 PM

8-1
8
EBU28788
PERIODIC MAINTENANCE AND ADJUSTMENT
EBU21675Periodic inspection, adjustment, and lubrication
will keep your vehicle in the safest and most effi-
cient condition possible. Safety is an obligation of
the vehicle owner/operator. The most important
points of vehicle inspection, adjustment, and lu-
brication are explained on the following pages.
WARNING
EWB01842Failure to properly maintain the vehicle or per-
forming maintenance activities incorrectly may
increase your risk of injury or death during ser-
vice or while using the vehicle. If you are not fa-
miliar with vehicle service, have a Yamaha
dealer perform the service.
WARNING
EWB02563Turn off the engine when performing mainte-
nance unless otherwise specified.
A running engine has moving parts that can
catch on body parts or clothing and electri-
cal parts that can cause shocks or fires. 
Running the engine while servicing can lead
to eye injury, burns, fire, or carbon monoxide
poisoning - possibly leading to death. See
page 2-6 for more information about carbon
monoxide.

WARNING
EWB02691Brake discs, calipers, drums, and linings can
become very hot during use. To avoid possible
burns, let brake components cool before
touching them. The intervals given in the periodic maintenance
charts should be considered as a general guide
under normal riding conditions. However, DE-
PENDING ON THE WEATHER, TERRAIN, GEO-
GRAPHICAL LOCATION, AND INDIVIDUAL USE,
THE MAINTENANCE INTERVALS MAY NEED TO
BE SHORTENED.
UBD362E0.book Page 1 Tuesday, January 31, 2017 5:10 PM