YZ250FN

5NL-28199-10

LIT-11626-14-46

OWNER’S SERVICE MANUAL

YZ250FN

OWNER’S SERVICE MANUAL

©2000 by Yamaha Motor Corporation, U.S.A.

1st Edition, September 2000

All rights reserved.

Any reprinting or unauthorized use

without the written permission of

Yamaha Motor Corporation U.S.A.

is expressly prohibited.

Printed in Japan

P/N. LIT-11626-14-46

EC020000

INTRODUCTION

Congratulations on your purchase of a

Yamaha YZ series. This model is the culmina-

tion of Yamaha’s vast experience in the pro-

duction of pacesetting racing machines. It

represents the highest grade of craftsmanship

and reliability that have made Yamaha a

leader.

This manual explains operation, inspection,

basic maintenance and tuning of your

machine. If you have any questions about this

manual or your machine, please contact your

Yamaha dealer.

NOTE:

As improvements are made on this model,

some data in this manual may become out-

dated. If you have any questions, please con-

sult your Yamaha dealer.

WARNING

PLEASE READ THIS MANUAL CAREFULLY

AND COMPLETELY BEFORE OPERATING

THIS MACHINE. DO NOT ATTEMPT TO

OPERATE THIS MACHINE UNTIL YOU

HAVE

ATTAINED

A

SATISFACTORY

KNOWLEDGE OF ITS CONTROLS AND

OPERATING FEATURES AND UNTIL YOU

HAVE BEEN TRAINED IN SAFE AND

PROPER RIDING TECHNIQUES. REGULAR

INSPECTIONS AND CAREFUL MAINTE-

NANCE, ALONG WITH GOOD RIDING

SKILLS, WILL ENSURE THAT YOU SAFETY

ENJOY THE CAPABILITIES AND THE RELI-

ABILITY OF THIS MACHINE.

IMPORTANT NOTICE

THIS MACHINE IS DESIGNED STRICTLY

FOR COMPETITION USE, ONLY ON A

CLOSED COURSE. It is illegal for this

machine to be operated on any public street,

road, or highway. Off-road use on public lands

may also be illegal. Please check local regula-

tions before riding.

1. THIS MACHINE IS TO BE OPERATED

BY AN EXPERIENCED RIDER ONLY.

Do not attempt to operate this

machine at maximum power until you

are totally familiar with its character-

istics.

2. THIS MACHINE IS DESIGNED TO BE

RIDDEN BY THE OPERATOR ONLY.

Do not carry passengers on this

machine.

3. ALWAYS WEAR PROTECTIVE

APPAREL.

When operating this machine, always

wear an approved helmet with gog-

gles or a face shield. Also wear heavy

boots, gloves, and protective cloth-

ing. Always wear proper fitting cloth-

ing that will not be caught in any of

the moving parts or controls of the

machine.

4. ALWAYS MAINTAIN YOUR MACHINE

IN PROPER WORKING ORDER.

For safety and reliability, the machine

must be properly maintained. Always

perform the pre-operation checks

indicated in this manual. Correcting a

mechanical problem before you ride

may prevent an accident.

5. GASOLINE IS HIGHLY FLAMMABLE.

Always turn off the engine while refu-

eling. Take care to not spill any gaso-

line on the engine or exhaust system.

Never refuel in the vicinity of an open

flame, or while smoking.

SAFETY INFORMATION

6. GASOLINE CAN CAUSE INJURY.

If you should swallow some gasoline,

inhale excess gasoline vapors, or

allow any gasoline to get into your

eyes, contact a doctor immediately. If

any gasoline spills onto your skin or

clothing, immediately wash skin areas

with soap and water, and change your

clothes.

7. ONLY OPERATE THE MACHINE IN AN

AREA WITH ADEQUATE VENTILA-

TION.

Never start the engine or let it run for

any length of time in an enclosed area.

Exhaust fumes are poisonous. These

fumes

contain

carbon

monoxide,

which by itself is odorless and color-

less. Carbon monoxide is a dangerous

gas which can cause unconscious-

ness or can be lethal.

8. PARK THE MACHINE CAREFULLY;

TURN OFF THE ENGINE.

Always turn off the engine if you are

going to leave the machine. Do not

park the machine on a slope or soft

ground as it may fall over.

9. THE ENGINE EXHAUST PIPE, MUF-

FLER, AND OIL TANK WILL BE VERY

HOT AFTER THE ENGINE HAS BEEN

RUN.

Be careful not to touch them or to

allow any clothing item to contact

them during inspection or repair.

10. PROPERLY SECURE THE MACHINE

BEFORE TRANSPORTING IT.

When transporting the machine in

another vehicle, always be sure it is

properly secured and in an upright

position and that the fuel cock is in

the “OFF” position. Otherwise, fuel

may leak out of the carburetor or fuel

tank.

EC050000

TO THE NEW OWNER

This manual will provide you with a good basic

understanding of features, operation, and

basic maintenance and inspection items of this

machine. Please read this manual carefully

and completely before operating your new

machine. If you have any questions regarding

the operation or maintenance of your machine,

please consult your Yamaha dealer.

NOTE:

This manual should be considered a perma-

nent part of this machine and should remain

with it even if the machine is subsequently

sold.

EC060000

NOTICE

Some data in this manual may become out-

dated due to improvements made to this

model in the future. If there is any question

you have regarding this manual or your

machine, please consult your Yamaha

dealer.

EC070001

F.I.M. MACHINE WEIGHTS:

Weights of machines without fuel

The

minimum

weights

for

motocross

machines are:

for the class 125 cc.......................minimum

88 kg (194 lb)

for the class 250 cc.......................minimum

98 kg (216 lb)

for the class 500 cc.......................minimum

102 kg (225 lb)

In modifying your machine (e.g., for weight

reduction), take note of the above limits of

weight.

EC080000

HOW TO USE

THIS MANUAL

EC081000

PARTICULARLY IMPORTANT

INFORMATION

The Safety Alert Symbol means ATTENTION!

BECOME

ALERT!

YOUR

SAFETY

IS

INVOLVED!

Failure to follow WARNING instructions could

result in severe injury or death to the machine

operator, a bystander, or a person inspecting

or repairing the machine.

A CAUTION indicates special precautions that

must be taken to avoid damage to the

machine.

NOTE:

A NOTE provides key information to make pro-

cedures easier or clearer.

WARNING

CAUTION:

EC082000

FINDING THE REQUIRED PAGE

1. This manual consists of seven chapters;

“General information”, “Specifications”,

“Regular inspection and adjustments”,

“Engine”,

“Chassis”,

“Electrical”

and

“Tuning”.

2. The table of contents is at the beginning

of the manual. Look over the general lay-

out of the book before finding then

required chapter and item.

Bend the book at its edge, as shown, to

find the required fore edge symbol mark

and go to a page for required item and

description.

EC083000

MANUAL FORMAT

All of the procedures in this manual are organized in a sequential, step-by-step format. The informa-

tion has been complied to provide the mechanic with an easy to read, handy reference that contains

comprehensive explanations of all disassembly, repair, assembly, and inspection operations.

In this revised format, the condition of a faulty component will precede an arrow symbol and the

course of action required will follow the symbol, e.g.,

G Bearings

Pitting/damage → Replace.

EC084002

HOW TO READ DESCRIPTIONS

To help identify parts and clarify procedure steps, there are exploded diagrams at the start of each

removal and disassembly section.

1. An easy-to-see exploded diagram 1 is provided for removal and disassembly jobs.

2. Numbers 2 are given in the order of the jobs in the exploded diagram. A number that is

enclosed by a circle indicates a disassembly step.

3. An explanation of jobs and notes is presented in an easy-to-read way by the use of symbol

marks 3. The meanings of the symbol marks are given on the next page.

4. A job instruction chart 4 accompanies the exploded diagram, providing the order of jobs,

names of parts, notes in jobs, etc.

5. Extent of removal 5 is provided in the job instruction chart to save the trouble of an unneces-

sary removal job.

6. For jobs requiring more information, the step-by-step format supplements 6 are given in addi-

tion to the exploded diagram and job instruction chart.

ILLUSTRATED SYMBOLS

(Refer to the illustration)

Illustrated symbols 1 to 7 are designed as

thumb tabs to indicate the chapter’s number

and content.

1 General information

2 Specifications

3 Regular inspection and adjustments

4 Engine

5 Chassis

6 Electrical

7 Tuning

Illustrated symbols 8 to D are used to identify

the specifications appearing in the text.

8 With engine mounted

9 Special tool

0 Filling fluid

A Lubricant

B Tightening

C Specified value, Service limit

D Resistance (Ω), Voltage (V), Electric current (A)

Illustrated symbols E to H in the exploded

diagrams indicate grade of lubricant and loca-

tion of lubrication point.

E Apply engine oil

F Apply molybdenum disulfide oil

G Apply lightweight lithium-soap base grease

H Apply molybdenum disulfide grease

Illustrated symbols I to J in the exploded

diagrams indicate where to apply a locking

agent and where to install new parts.

I Apply locking agent (LOCTITE^®)

J Use new one

1

2

3

4

5

6

7

8

9

0

A

B

C

D

E

F

G

H

I

J

GEN

INFO

SPEC

INSP

ADJ

ENG

CHAS

–

+

ELEC

TUN

T R

.

.

E

M

B

M

MEMO

EC090000

INDEX

GENERAL INFORMATION

1

SPECIFICATIONS

SPEC 2

REGULAR INSPECTION AND ADJUSTMENTS

3

ENGINE

ENG 4

CHASSIS

CHAS 5

ELECTRICAL

ELEC 6

TUNING

TUN 7

GEN

INFO

INSP

ADJ

–

+

EC0A0000

CONTENTS

CHAPTER 1

GENERAL INFORMATION

DESCRIPTION ..........................................1-1

MACHINE IDENTIFICATION ....................1-2

IMPORTANT INFORMATION ...................1-3

CHECKING OF CONNECTION .................1-6

SPECIAL TOOLS ......................................1-7

CONTROL FUNCTIONS .........................1-10

FUEL .......................................................1-13

STARTING AND BREAK-IN ...................1-14

TORQUE-CHECK POINTS .....................1-18

CLEANING AND STORAGE ...................1-19

CHAPTER 2

SPECIFICATIONS

GENERAL SPECIFICATIONS ..................2-1

MAINTENANCE SPECIFICATIONS .........2-4

GENERAL TORQUE

SPECIFICATIONS ...................................2-17

DEFINITION OF UNITS ...........................2-17

CABLE ROUTING DIAGRAM .................2-18

CHAPTER 3

REGULAR INSPECTION AND

ADJUSTMENTS

MAINTENANCE INTERVALS ...................3-1

PRE-OPERATION INSPECTION AND

MAINTENANCE ........................................3-4

ENGINE .....................................................3-5

CHASSIS .................................................3-25

ELECTRICAL ..........................................3-46

CHAPTER 4

ENGINE

SEAT, FUEL TANK

AND SIDE COVERS .................................4-1

EXHAUST PIPE AND SILENCER ............4-2

RADIATOR ................................................4-4

CARBURETOR .........................................4-7

CAMSHAFTS ..........................................4-19

CYLINDER HEAD ...................................4-28

VALVES AND VALVE SPRINGS ...........4-32

CYLINDER AND PISTON .......................4-41

CLUTCH ..................................................4-48

OIL FILTER ELEMENT,

WATER PUMP AND RIGHT

CRANKCASE COVER ............................4-55

BALANCER .............................................4-62

OIL PUMP ...............................................4-65

KICK SHAFT AND SHIFT SHAFT ..........4-70

CDI MAGNETO .......................................4-77

ENGINE REMOVAL ................................4-81

CRANKCASE AND CRANKSHAFT .......4-86

TRANSMISSION, SHIFT CAM

AND SHIFT FORK ..................................4-95

CHAPTER 5

CHASSIS

FRONT WHEEL AND REAR WHEEL .......5-1

FRONT BRAKE AND REAR BRAKE .....5-10

FRONT FORK .........................................5-27

HANDLEBAR ..........................................5-40

STEERING ..............................................5-45

SWINGARM ............................................5-50

REAR SHOCK ABSORBER ...................5-57