Yamaha 2003 YFZ450S User manual

YFZ450S
5TG2-AE1
SERVICE MANUAL

EBS00000
YFZ450S
SERVICE MANUAL
©2003 by Yamaha Motor Co., Ltd.
First Edition, April 2003
All rights reserved.
Any reproduction or unauthorized use
without the written permission of
Yamaha Motor Co., Ltd.
is expressly prohibited.

EBS00002
NOTICE
This manual was produced by the Yamaha Motor Company primarily for use by Yamaha dealers
and their qualified mechanics. It is not possible to include all the knowledge of a mechanic in one
manual, so it is assumed that anyone who uses this book to perform maintenance and repairs on
Yamaha machine has a basic understanding of the mechanical ideas and the procedures of
machine repair. Repairs attempted by anyone without this knowledge are likely to render the
machine unsafe and unfit for use.
Yamaha Motor Company, Ltd. is continually striving to improve all its models. Modifications and sig-
nificant changes in specifications or procedures will be forwarded to all authorized Yamaha dealers
and will appear in future editions of this manual where applicable.
NOTE:
_
Designs and specifications are subject to change without notice.
EBS00003
IMPORTANT INFORMATION
Particularly important information is distinguished in this manual by the following notations.
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 checking or repairing the
machine.
A CAUTION indicates special precautions that must be taken to avoid damage
to the machine.
A NOTE provides key information to make procedures easier or clearer.
WARNING
CAUTION:
NOTE:

EBS00004
HOW TO USE THIS MANUAL
MANUAL ORGANIZATION
This manual consists of chapters for the main categories of subjects. (See “symbols”)
1st title 1: This is the title of the chapter with its symbol in the upper right corner of each page.
2nd title 2: This title indicates the section of the chapter and only appears on the first page of each
section. It is located in the upper left corner of the page.
3rd title 3: This title indicates a sub-section that is followed by step-by-step procedures accompa-
nied by corresponding illustrations.
EXPLODED DIAGRAMS
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 4is provided for removal and disassembly jobs.
2. Numbers 5are 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
6. The meanings of the symbol marks are given on the next page.
4. A job instruction chart 7accompanies the exploded diagram, providing the order of jobs, names
of parts, notes in jobs, etc.
5. For jobs requiring more information, the step-by-step format supplements 8are given in addition
to the exploded diagram and the job instruction chart.

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SYMBOLS
The following symbols are not relevant to
every machine.
Symbols 1to 9indicate the subject of each
chapter.
1General information
2Specifications
3Periodic checks and adjustments
4Engine
5Cooling system
6Carburetor
7Chassis
8Electrical
9Troubleshooting
Symbols 0to Gindicate the following
0Serviceable with engine mounted
AFilling fluid
BLubricant
CSpecial tool
DTorque
EWear limit, clearance
FEngine speed
GElectrical data (Ω, V, A)
Symbols Hto Nin the exploded diagrams
indicate the types of lubricants and lubrication
points.
HApply engine oil
IApply gear oil
JApply molybdenum disulfide oil
KApply wheel bearing grease
LApply lithium-soap-based grease
MApply molybdenum disulfide grease
Symbols Nto Oin the exploded diagrams
indicate where to apply a locking agent Nand
when to install a new part O.
NApply the locking agent (LOCTITE®)
OReplace
12
34
56
78
90
AB
CD
EFG
HIJ
KLM
NO
GEN
INFO SPEC
CHK
ADJ ENG
COOL CARB
CHAS
–+
ELEC
TRBL
SHTG
T
R
.
.
EGM
BLS M
LT
New

EBS00008
TABLE OF CONTENTS
GENERAL INFORMATION GEN
INFO 1
SPECIFICATIONS SPEC 2
PERIODIC CHECKS AND
ADJUSTMENTS CHK
ADJ 3
ENGINE ENG 4
COOLING SYSTEM COOL 5
CARBURETOR CARB 6
CHASSIS CHAS 7
ELECTRICAL ELEC 8
TROUBLESHOOTING TRBL
SHTG
9
–+

GEN
INFO 1

GEN
INFO
CHAPTER 1
GENERAL INFORMATION
MACHINE IDENTIFICATION...........................................................................1-1
VEHICLE IDENTIFICATION NUMBER .....................................................1-1
MODEL LABEL..........................................................................................1-1
IMPORTANT INFORMATION .........................................................................1-2
PREPARATION FOR REMOVAL AND DISASSEMBLY........................... 1-2
REPLACEMENT PARTS...........................................................................1-2
GASKETS, OIL SEALS AND O-RINGS ....................................................1-2
LOCK WASHERS/PLATES AND COTTER PINS .....................................1-3
BEARINGS AND OIL SEALS ....................................................................1-3
CIRCLIPS ..................................................................................................1-3
CHECKING THE CONNECTIONS............................................................1-4
SPECIAL TOOLS ............................................................................................1-5

GEN
INFO

1 - 1
GEN
INFO
MACHINE IDENTIFICATION
EBS00009
GENERAL INFORMATION
MACHINE IDENTIFICATION
EBS00010
VEHICLE IDENTIFICATION NUMBER
The vehicle identification number 1is
stamped into the left side of the frame.
1
EBS00011
MODEL LABEL
The model label 1is affixed to the air filter
case cover. This information will be needed to
order spare parts.
1

1 - 2
GEN
INFO
IMPORTANT INFORMATION
EBS00013
IMPORTANT INFORMATION
PREPARATION FOR REMOVAL AND
DISASSEMBLY
1. Before removal and disassembly remove all
dirt, mud, dust and foreign material.
2. Use only the proper tools and cleaning
equipment.
Refer to “SPECIAL TOOLS”.
3. When disassembling always keep mated
parts together. This includes gears, cylin-
ders, pistons and other parts that have been
“mated” through normal wear. Mated parts
must always be reused or replaced as an
assembly.
4. During disassembly, clean all of the parts
and place them in trays in the order of dis-
assembly. This will speed up assembly and
allow for the correct installation of all parts.
5. Keep all parts away from any source of fire.
EBS00014
REPLACEMENT PARTS
1. Use only genuine Yamaha parts for all
replacements. Use oil and grease recom-
mended by Yamaha for all lubrication jobs.
Other brands may be similar in function and
appearance, but inferior in quality.
EBS00015
GASKETS, OIL SEALS AND O-RINGS
1. When overhauling the engine, replace all
gaskets, seals and O-rings. All gasket sur-
faces, oil seal lips and O-rings must be
cleaned.
2. During reassembly properly oil all mating
parts and bearings, and lubricate the oil
seal lips with grease.

1 - 3
GEN
INFO
IMPORTANT INFORMATION
EBS00016
LOCK WASHERS/PLATES AND COTTER
PINS
After removal, replace all lock washers/plates
1and cotter pins. After the bolt or nut has
been tightened to specification, bend the lock
tabs along a flat of the bolt or nut.
EBS00017
BEARINGS AND OIL SEALS
Install bearings and oil seals so that the manu-
facturer’s marks or numbers are visible. When
installing oil seals, lubricate the oil seal lips
with a light coat of lithium-soap-based grease.
Oil bearings liberally when installing, if appro-
priate.
1Oil seal
CAUTION:
_
Do not spin the bearing with compressed
air because this will damage the bearing
surfaces.
1Bearing
EBS00018
CIRCLIPS
Before reassembly, check all circlips carefully
and replace damaged or distorted circlips.
Always replace piston pin clips after one use.
When installing a circlip 1, make sure the
sharp-edged corner 2is positioned opposite
the thrust 3that the circlip receives.
4Shaft

1 - 4
GEN
INFO
IMPORTANT INFORMATION
EBS00019
CHECKING THE CONNECTIONS
Check the leads, couplers, and connectors for
stains, rust, moisture, etc.
1. Disconnect:
•lead
•coupler
•connector
2. Check:
•lead
•coupler
•connector
Moisture →Dry with an air blower.
Rust/stains →Connect and disconnect sev-
eral times.
3. Check:
•all connections
Loose connection →Connect properly.
NOTE:
_
If the pin 1on the terminal is flattened, bend it
up.
4. Connect:
•lead
•coupler
•connector
NOTE:
_
Make sure all connections are tight.
5. Check:
•continuity (with the pocket tester)
NOTE:
_
•If there is no continuity, clean the terminals.
•When checking the wire harness, perform
steps (1) to (3).
•As a quick remedy, use a contact revitalizer
available at most part stores.
Pocket tester
P/N. YU-03112-C, 90890-03112

1 - 5
GEN
INFO
SPECIAL TOOLS
EBS00021
SPECIAL TOOLS
The following special tools are necessary for complete and accurate tune-up and assembly. Use
only the appropriate special tools; this will help prevent damage caused by the use of inappropriate
tools or improvised techniques. Special tools may differ by shape and part number from country to
country. In such a case, two types are provided.
When placing an order, refer to the list provided below to avoid any mistakes.
For US and CDN
P/N. YM-, YU-, YS-, YK-, ACC-
Except for US and CDN
P/N. 90890-
Tool No. Tool name/Function Illustration
90890-01135
YU-01135-A
Crankcase separating tool
This tool is used to separate the crank-
case.
Pot
90890-01274
Bolt
90890-01275
Crankshaft installer pot
Crankshaft installer bolt
These tools are used to install the crank-
shaft.
YU-90050
Crankshaft installer set
These tools are used to install the crank-
shaft.
Adapter
90890-01278
YM-90063
Spacer
90890-04081
YM-91044
Adapter
Spacer (crankshaft installer)
These tools are used to install the crank-
shaft.
90890-01304
YU-01304
Piston pin puller
This tool is used to remove the piston pin.
90890-01325
YU-24460-01
Radiator cap tester
This tool is used to check the cooling sys-
tem.

1 - 6
GEN
INFO
SPECIAL TOOLS
90890-01352
YU-33984
Radiator cap tester adapter
This tool is used to check the cooling sys-
tem.
90890-01327
YM-01327
Damper rod holder (30 mm)
This tool is needed to loosen and tighten
the steering stem bearing retainer.
90890-01443
YU-33975
Steering nut wrench
This tool is needed to loosen and tighten
the front shock absorber and rear shock
absorber locknuts.
90890-01474
YM-01474
Ball joint remover/installer set
These tools are used to removing or
installing the ball joints.
90890-01480
YM-01480
Ball joint remover/installer attachment set
These tools are used to removing or
installing the ball joints.
90890-01701
YS-01880-A
Sheave holder
This tool is needed to hold the A.C. mag-
neto rotor when loosen or tighten the A.C.
magneto rotor nut.
90890-03112
YU-03112-C
Pocket tester
This instrument is needed for checking the
electrical system.
90890-03141
YM-33277-A
Timing light
This tool is necessary for checking ignition
timing.
Tool No. Tool name/Function Illustration

1 - 7
GEN
INFO
SPECIAL TOOLS
Compressor
90890-04019
YM-04019
Attachment
90890-04114
YM-04114
Valve spring compressor
Valve spring compressor attachment
This tool is needed to remove and install
the valve assemblies.
90890-04086
YM-91042
Universal clutch holder
This tool is needed to hold the clutch car-
rier when removing or installing the carrier
nut.
90890-04097
YM-04097
90890-04116
YM-04116
Valve guide remover (ø5)
Valve guide remover (ø4.5)
This tool is needed to remove and install
the valve guides.
90890-04098
YM-04098
90890-04117
YM-04117
Valve guide installer (ø5)
Valve guide installer (ø4.5)
This tool is needed to install the valve
guides.
90890-04099
YM-04099
90890-04118
YM-04118
Valve guide reamer (ø5)
Valve guide reamer (ø4.5)
This tool is needed to rebore the new
valve guides.
90890-04101
Valve lapper
This tool is needed to remove and install
the valve lifters.
90890-04142
YM-04142
Rotor puller
These tools are needed to remove the
A.C. magneto rotor.
90890-06588
PTT wrench 46
This tool is needed to loosen or tighten the
rear axle nut.
Tool No. Tool name/Function Illustration

1 - 8
GEN
INFO
SPECIAL TOOLS
YM-37134
Axle nut wrench (46 mm)
This tool is needed to loosen or tighten the
rear axle nut.
90890-06754
Ignition checker
This instrument is necessary for checking
the ignition system components.
YM-34487
Dynamic spark tester
This instrument is necessary for checking
the ignition system components.
Bond
90890-85505
Sealant
ACC-11001-05-01
Yamaha bond No. 1215
Sealant (Quick Gasket®)
This sealant (bond) is used on crankcase
mating surfaces, etc.
Tool No. Tool name/Function Illustration