Yamaha 2003 YZ450FR Application guide

LIT-11626-16-38
YZ450FR
5TA-28199-10
OWNER’S SERVICE MANUAL

EC010000
YZ450FR
OWNER’S SERVICE MANUAL
©2002 by Yamaha Motor Corporation, U.S.A.
1st Edition, June 2002
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-11626-16-38

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.,
●
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
®
)
JUse new one
12
34
56
78
90
AB
CD
EF
GH
IJ
GEN
INFO SPEC
INSP
ADJ ENG
CHAS
–+
ELEC
TUN
T
R
.
.
EM
BM
New

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 ................................... 2-18
DEFINITION OF UNITS ........................... 2-18
LUBRICATION DIAGRAMS ................... 2-19
CABLE ROUTING DIAGRAM ................. 2-21
CHAPTER 3
REGULAR INSPECTION AND
ADJUSTMENTS
MAINTENANCE INTERVALS ................... 3-1
PRE-OPERATION INSPECTION
AND MAINTENANCE ............................... 3-4
ENGINE ..................................................... 3-5
CHASSIS ................................................. 3-24
ELECTRICAL .......................................... 3-45

CHAPTER 4
ENGINE
SEAT, FUEL TANK
AND SIDE COVERS ................................. 4-1
EXHAUST PIPE AND SILENCER ............ 4-3
RADIATOR ................................................ 4-5
CARBURETOR ......................................... 4-8
CAMSHAFTS .......................................... 4-21
CYLINDER HEAD ................................... 4-29
VALVES AND VALVE SPRINGS ........... 4-33
CYLINDER AND PISTON ....................... 4-42
CLUTCH .................................................. 4-48
OIL FILTER, WATER PUMP
AND CRANKCASE COVER (RIGHT) ..... 4-55
BALANCER ............................................. 4-62
OIL PUMP ............................................... 4-65
KICK AXLE AND SHIFT SHAFT ............ 4-69
CDI MAGNETO ....................................... 4-76
ENGINE REMOVAL ................................ 4-80
CRANKCASE AND CRANKSHAFT ....... 4-85
TRANSMISSION, SHIFT CAM
AND SHIFT FORK .................................. 4-94
CHAPTER 5
CHASSIS
FRONT WHEEL AND REAR WHEEL ...... 5-1
FRONT BRAKE AND REAR BRAKE ..... 5-10
FRONT FORK ......................................... 5-26
HANDLEBAR .......................................... 5-39
STEERING .............................................. 5-45
SWINGARM ............................................ 5-50
REAR SHOCK ABSORBER ................... 5-58

CHAPTER 6
ELECTRICAL
ELECTRICAL COMPONENTS
AND WIRING DIAGRAM .......................... 6-1
MAP-CONTROLLED CDI UNIT ................ 6-2
IGNITION SYSTEM ................................... 6-3
TPS (THROTTLE POSITION SENSOR)
SYSTEM .................................................... 6-7
CHAPTER 7
TUNING
ENGINE ..................................................... 7-1
CHASSIS ................................................. 7-10

GEN
INFO
1 - 1
DESCRIPTION
EC100000
GENERAL INFORMATION
EC110000
DESCRIPTION
1 Clutch lever
2 Hot starter lever
3 Front brake lever
4 Throttle grip
5 Radiator cap
6 Fuel tank cap
7 “ENGINE STOP” button
8 Kick starter
9 Fuel tank
0 Radiator
A Coolant drain bolt
B Rear brake pedal
C Valve joint
D Fuel cock
E Cold starter knob
F Drive chain
G Air cleaner
H Shift pedal
I Oil dipstick
J Front fork
NOTE:
●
The machine you have purchased may differ
slightly from those shown in the following.
●
Designs and specifications are subject to
change without notice.
1

1 - 2
GEN
INFO
MACHINE IDENTIFICATION
EC120001
MACHINE IDENTIFICATION
There are two significant reasons for knowing
the serial number of your machine:
1. When ordering parts, you can give the
number to your Yamaha dealer for posi-
tive identification of the model you own.
2. If your machine is stolen, the authorities
will need the number to search for and
identify your machine.
EC121001
VEHICLE IDENTIFICATION NUMBER
The vehicle identification number 1 is
stamped on the right of the steering head pipe.
EC123001
ENGINE SERIAL NUMBER
The engine serial number 1 is stamped into
the elevated part of the right-side of the
engine.
EC124000
MODEL LABEL
The model label 1 is affixed to the frame
under the rider’s seat. This information will be
needed to order spare parts.

1 - 3
GEN
INFO
IMPORTANT INFORMATION
EC130000
IMPORTANT INFORMATION
EC131010
PREPARATION FOR REMOVAL AND
DISASSEMBLY
1. Remove all dirt, mud, dust, and foreign
material before removal and disassem-
bly.
When washing the machine with high
pressured water, cover the parts as fol-
lows.
●
Silencer exhaust port
●
Side cover air intake port
●
Water pump housing hole at the bottom
●
Drain hole on the cylinder head (right
side)
2. Use proper tools and cleaning equip-
ment. Refer to “SPECIAL TOOLS”sec-
tion.
3. When disassembling the machine, keep
mated parts together. They include
gears, cylinders, pistons, and other
mated parts that have been “mated”
through normal wear. Mated parts must
be reused as an assembly or replaced.
4. During the machine disassembly, clean
all parts and place them in trays in the
order of disassembly. This will speed up
assembly time and help assure that all
parts are correctly reinstalled.
5. Keep away from fire.

1 - 4
GEN
INFO
IMPORTANT INFORMATION
EC132000
ALL REPLACEMENT PARTS
1. We recommend to use Yamaha genuine
parts for all replacements. Use oil and/or
grease recommended by Yamaha for
assembly and adjustment.
EC133000
GASKETS, OIL SEALS AND O-RINGS
1. All gaskets, oil seals, and O-rings should
be replaced when an engine is over-
hauled. All gasket surfaces, oil seal lips,
and O-rings must be cleaned.
2. Properly oil all mating parts and bearings
during reassembly. Apply grease to the
oil seal lips.
EC134000
LOCK WASHERS/PLATES AND COTTER
PINS
1. All lock washers/plates 1 and cotter pins
must be replaced when they are
removed. Lock tab(s) should be bent
along the bolt or nut flat(s) after the bolt
or nut has been properly tightened.
EC135001
BEARINGS AND OIL SEALS
1. Install the bearing(s) 1 and oil seal(s) 2
with their manufacturer’s marks or num-
bers facing outward. (In other words, the
stamped letters must be on the side
exposed to view.) When installing oil
seal(s), apply a light coating of light-
weight lithium base grease to the seal
lip(s). Oil the bearings liberally when
installing.
CAUTION:
Do not use compressed air to spin the
bearings dry. This causes damage to the
bearing surfaces.