YAMAHA YFM90 2018 Service Manual

4-9
4
of sparks, open flames, or other sources of
ignition such as the pilot lights of water heat-
ers and clothes dryers.
2. Do not overfill the fuel tank. When refueling, be sure to insert the pump nozzle into the fuel
tank filler hole. Stop filling when the fuel
reaches the bottom of the filler tube. Because
fuel expands when it heats up, heat from the
engine or the sun can cause fuel to spill out of
the fuel tank. For Europe
TIPWhen refueling, check that the gasoline pump
nozzle has same fuel identification mark.
1. Maximum fuel level
2. Fuel tank filler tube
12
Recommended fuel:
Regular unleaded gasoline only
Fuel tank capacity: 6.6 L (1.74 US gal, 1.45 Imp.gal)
Fuel reserve amount: 0.9 L (0.24 US gal, 0.20 Imp.gal)1. EN228 fuel identification mark
E10
1
UBD362E0.book Page 9 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
UBD362E0.book Page 10 Tuesday, January 31, 2017 5:10 PM

4-11
4
With the fuel cock lever in this position, fuel will not
flow. Always turn the fuel cock lever to this posi-
tion when the engine is not running.
ON
With the fuel cock lever in this position, fuel flows
to the carburetor. Turn the fuel cock lever to this
position when starting the engine and riding. RES
This indicates reserve. With the fuel cock lever in
this position, the fuel reserve is made available.
Turn the fuel cock lever to this position if you run
out of fuel while riding. When this occurs, refuel as
soon as possible and be sure to turn the fuel cock
lever back to “ON”!
EBU18852Starter (choke) “ ”Starting a cold engine requires a richer air-fuel
mixture. This mixture is controlled by the starter
(choke) system.
1. Arrow mark positioned over “ON”
1
1. Arrow mark positioned over “RES”
1
UBD362E0.book Page 11 Tuesday, January 31, 2017 5:10 PM

4-12
4To use the starter (choke) and enrich the air-fuel
ratio, move the starter (choke) lever in direction (a).
To decrease the starter (choke) or turn it off, move
the starter (choke) lever in direction (b).
TIPSee page 6-1 for engine starting instructions.
EBU34551SeatTo remove the seat
Push down on the rear of the seat and pull the seat
lock lever upward to release the seat lock. Then
pull up at the rear of the seat to remove it.
1. Starter (choke) lever
1
(a) (b)
1. Seat
2. Seat lock lever
1
2
UBD362E0.book Page 12 Tuesday, January 31, 2017 5:10 PM

4-13
4
To install the seat
Insert the projection on the front of the seat into
the seat holder, and then push down on the seat
at the rear to lock it in place. Make sure that the
seat is securely fitted.
EBU18995Adjusting the front shock absorber as-
sembliesThe spring preload can be adjusted to suit the rid-
er’s weight and the riding conditions.
WARNING
EWB00401Always adjust the shock absorber assemblies
on the left and right side to the same setting.
Uneven adjustment can cause poor handling
and loss of stability, which could lead to an ac-
cident. NOTICEECB01091Never turn the adjusting mechanism beyond
the minimum and maximum settings. Adjust the spring preload as follows.
Turn the spring preload adjusting ring in direction
(a) to increase the spring preload and thereby
harden the suspension, and in direction (b) to de-
crease the spring preload and thereby soften the
suspension.
Align the appropriate notch in the adjusting ring
with the position indicator on the shock absorber.
1. Projection
2. Seat holder
1
2
UBD362E0.book Page 13 Tuesday, January 31, 2017 5:10 PM

4-14
4
TIPA special wrench can be obtained at a Yamaha
dealer to make this adjustment.
EBU19025Adjusting the rear shock absorberThe spring preload can be adjusted to suit the rid-
er’s weight and the riding conditions.
1. Spring preload adjusting ring
2. Position indicator
123 45
2
1(a)
(b)
1. Special wrenchSpring preload setting:
Minimum (soft):1
Standard: 3
Maximum (hard): 5
1
UBD362E0.book Page 14 Tuesday, January 31, 2017 5:10 PM

4-15
4
NOTICEECB01091Never turn the adjusting mechanism beyond
the minimum and maximum settings. Adjust the spring preload as follows.
Turn the spring preload adjusting ring in direction
(a) to increase the spring preload and thereby
harden the suspension, and in direction (b) to de-
crease the spring preload and thereby soften the
suspension.
TIPA special wrench can be obtained at a Yamaha
dealer to make this adjustment.
1. Spring preload adjusting ring
2. Position indicator
123 45
2
1
(a)
(b)
1. Special wrenchSpring preload setting:
Minimum (soft):1
Standard: 2
Maximum (hard): 5
1
UBD362E0.book Page 15 Tuesday, January 31, 2017 5:10 PM

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

5-2
5
Throttle lever• Make sure that operation is smooth. Lubricate cable and lever
housing if necessary.
• Check lever free play, and adjust if necessary. 5-3, 8-20
Control cables • Make sure that operation is smooth. Lubricate if necessary. 8-28
Drive chain • Check chain slack, and adjust if necessary.
• Check chain condition. Lubricate if necessary. 5-3, 8-25, 8-27
Wheels and tires • Check wheel condition, and replace if damaged.
• Check tire condition and tread depth. Replace if necessary.
• Check air pressure. Correct if necessary. 5-3
Brake levers • Make sure that operation is smooth. Lubricate lever pivoting points
if necessary. 8-29
Chassis fasteners • Make sure that all nuts, bolts and screws are properly tightened. 5-6
Instruments and switches • Check operation, and correct if necessary. 5-6
ITEM ROUTINE PAGE
UBD362E0.book Page 2 Tuesday, January 31, 2017 5:10 PM

5-3
5
EBU19542FuelMake sure that there is sufficient fuel in the tank.
(See page 4-8.)EBU19561Engine oilMake sure that the engine oil is at the specified
level. Add oil as necessary. (See page 8-11.)EBU34490Transmission oilMake sure that the transmission oil is at the spec-
ified level. Add oil as necessary. (See page 8-14.)EBU19653Front and rear brakesBrake levers
Check for correct free play in the brake levers. If
the free play is incorrect, adjust it. (See pages
8-22 and 8-24.)
 Check operation of the levers. They should
move smoothly and there should be a firm feel-
ing when the brake is applied. If not, have the
ATV checked by a Yamaha dealer. Brake operation
Test the brakes at slow speed after starting out to
make sure they are working properly. If the brakes
do not provide proper braking performance,
check the brake shoes for wear. (See page 8-21.)
EBU19762Throttle leverCheck the operation of the throttle lever. It must
open smoothly and spring back to the idle position
when released. Have a Yamaha dealer correct if
necessary.EBU19771Drive chainCheck the condition of the drive chain and check
the drive chain slack. Lubricate and adjust the
drive chain as necessary. (See page 8-25.)EBU19797TiresCheck tire pressure regularly to make sure it is at
the recommended specifications. Also check for
wear and damage.
UBD362E0.book Page 3 Tuesday, January 31, 2017 5:10 PM