Page 6 of 418
EBU00946
1-INTRODUCTION
Congratulations on your purchase of the Yamaha
YFM400A. It represents the result of many years
of Yamaha experience in the production of fine
sporting, touring, and pacesetting racing ma-
chines. 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 un-
derstanding of the features and operation of this
ATV.
This manual includes important safety in-
formation. It provides information about spe-
cial techniques and skills necessary to ride
your ATV. It also includes basic maintenance and
inspection procedures. If you have any questions
regarding the operation or maintenance of your
ATV, please consult a Yamaha dealer.
U5VH60.book Page 4 Wednesday, August 7, 2002 12:00 PM
Page 17 of 418

Tire wear limit......................................5-33
OPERATION ...........................................6-1
Starting a cold engine ...........................6-3
Starting a warm engine .........................6-9
Warming up...........................................6-9
Drive select lever operation and
reverse driving ..................................6-11
Engine break-in ...................................6-17
Parking ................................................6-19
Parking on a slope ..............................6-21
Accessories and loading .....................6-23
RIDING YOUR ATV..................................7-1
Getting to know your ATV .....................7-3
Ride with care and good judgement .....7-5
Be careful where you ride ...................7-27
Turning your ATV ................................7-39
Climbing uphill.....................................7-45
Riding downhill ....................................7-55
Crossing a slope .................................7-59
Crossing through shallow water ..........7-63
Riding over rough terrain ....................7-69
Sliding and skidding ............................7-71
What to do if ........................................7-75
What to do...........................................7-75
67
PERIODIC MAINTENANCE AND
ADJUSTMENT ........................................ 8-1
Owner’s manual and tool kit ................. 8-3
Periodic maintenance/lubrication.......... 8-7
Panel removal and installation............ 8-15
Engine oil ............................................ 8-29
Final gear oil ....................................... 8-39
Cooling system ................................... 8-45
Changing the coolant.......................... 8-49
Spark plug inspection ......................... 8-57
Air filter element cleaning ................... 8-63
V-belt cooling duct check hose ........... 8-71
Carburetor adjustment ........................ 8-73
Idle speed adjustment ........................ 8-75
Valve clearance adjustment ............... 8-77
Throttle lever adjustment .................... 8-79
Front brake pad check ........................ 8-81
Rear brake shoe inspection ................ 8-81
Brake fluid level check ........................ 8-83
Brake fluid replacement ...................... 8-87
Front brake lever free play.................. 8-89
Rear brake pedal and lever
adjustment ........................................ 8-91
8
U5VH60.book Page 2 Wednesday, August 7, 2002 12:00 PM
Page 18 of 418

Adjusting the rear brake light
switch ............................................... 8-97
Cable inspection and lubrication ........ 8-99
Lubricating the brake levers and
brake pedal .................................... 8-101
Wheel removal ................................. 8-103
Wheel installation ............................. 8-105
Battery .............................................. 8-107
Battery maintenance ........................ 8-111
Fuse replacement............................. 8-113
Replacing a headlight bulb ............... 8-117
Headlight beam adjustment.............. 8-121
Tail/brake light bulb replacement ..... 8-121
Troubleshooting................................ 8-123
Troubleshooting chart....................... 8-125
CLEANING AND STORAGE .................. 9-1
A. Cleaning ........................................... 9-1
B. Storage ............................................ 9-7
SPECIFICATIONS ................................ 10-1
CONVERSION TABLE .......................... 11-1
91011U5VH60.book Page 3 Wednesday, August 7, 2002 12:00 PM
Page 40 of 418
2-5
Always inspect your ATV each time you use it
to make sure it is in safe operating condition.
Always follow the inspection and maintenance
procedures and schedules described in this
manual.
Always keep both hands on the handlebars
and both feet on the footboards of the ATV dur-
ing operation.
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
practiced the skills necessary to control the
ATV on such terrain. Always be especially cau-
tious 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. Do not turn at excessive speed.
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5-4
WARNING
Always inspect your ATV each time you use it to make sure the ATV is in safe operating condition.
Always follow the inspection and maintenance procedures and schedules described in the Own-
er’s Manual. Failure to inspect increases the possibility of an accident or equipment damage.
AVERTISSEMENT
_ Toujours effectuer ces contrôles avant chaque départ afin de s’assurer que le VTT peut être utilisé en toute sécu-
rité. Toujours respecter les procédés et intervalles de contrôle et d’entretien repris dans ce manuel. Omettre ces
contrôles accroît les risques d’accident ou d’endommagement du véhicule. _
ADVERTENCIA
Inspeccionar siempre el ATV cada vez que vaya a utilizarse, para asegurarse de que está en condicio-
nes de funcionar sin peligro. Seguir siempre los procedimientos y programas de inspección y mante-
nimiento descritos en el Manual del Propietario. Si no se inspecciona la máquina, aumenta el riesgo de
accidente o avería. _U5VH60.book Page 4 Wednesday, August 7, 2002 12:00 PM
Page 256 of 418
8-1
EBU00516
PERIODIC MAINTENANCE AND
ADJUSTMENTPeriodic inspection, adjustment and lubrication will
keep your machine in the safest and most efficient
condition possible. Safety is an obligation of the
machine owner. The most important points of ma-
chine inspection, adjustment and lubrication are
explained on the following pages.
WARNING
Never service an engine while it is running.
Moving parts can catch clothing or parts of the
body, causing injury. Electrical components
can cause shocks or can start fires. Turn off
the engine when performing maintenance un-
less otherwise specified. Have a Yamaha deal-
er perform service if you are not familiar with
machine service.
U5VH60.book Page 1 Wednesday, August 7, 2002 12:00 PM
Page 258 of 418

8-3 1. Owner’s manual
2. Owner’s tool kit
3. Low-pressure tire gauge
1. Manuel du propriétaire
2. Trousse à outils
3. Manomètre basse pression pour pneus
1. Manual del propietario
2. Juego de herramientas
3. Manómetro de baja presión
EBU01320
Owner’s manual and tool kit
You are recommended to put this owner’s manual
in the vinyl bag and always carry it on the bottom
of the seat as shown. Put the owner’s tool kit and
low-pressure tire gauge in the storage box.
The service information included in this manual is
intended to provide you, the owner, with the nec-
essary information for completing your own pre-
ventive maintenance and minor repairs. The tools
provided in the Owner’s tool kit are sufficient for
this purpose, except that a torque wrench is also
necessary to properly tighten nuts and bolts.NOTE:_ If you do not have a torque wrench available dur-
ing a service operation requiring one, take your
machine to a Yamaha dealer to check the torque
settings and adjust them as necessary. _
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8-7
EBU00262
PERIODIC MAINTENANCE/LUBRICATION
ITEM ROUTINEINITIAL EVERY
1
month3
months6
months6
months1
year
Valves*•Check valve clearance.
•Adjust if necessary.
Cooling system•Check coolant leakage.
•Repair if necessary.
•Replace coolant every 24 months.Spark plug•Check condition.
•Adjust gap and clean.
•Replace if necessary.Air filter element•Clean.
•Replace if necessary.Every 20–40 hours
(More often in wet or dusty areas.)
Carburetor*•Check and adjust idle speed/starter operation.
•Adjust if necessary.Crankcase breather
system*•Check breather hose for cracks or damage.
•Replace if necessary.Exhaust system*•Check for leakage.
•Tighten if necessary.
•Replace gasket(s) if necessary.Fuel line*•Check fuel hose for cracks or damage.
•Replace if necessary.Engine oil
•Replace. (Warm engine before draining.)Engine oil filter cartridge
•Replace.Engine oil strainer*
•Clean.Final gear oil•Check oil level/oil leakage.
•Replace every 12 months.Front brake*•Check operation/fluid leakage. (See NOTE page 8-8.)
•Correct if necessary.Rear brake•Check operation.
•Adjust if necessary.U5VH60.book Page 7 Wednesday, August 7, 2002 12:00 PM