Yamaha 2004 YP400 User manual

2004
YP400(S)
5RU1-AE1
SERVICE MANUAL

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YP400(S) 2004
SERVICE MANUAL
©2003 by Yamaha Motor Co., Ltd.
First edition, December 2003
All rights reserved.
Any reproduction or unauthorized use
without the written permission of
Yamaha Motor Co., Ltd.
is expressly prohibited.

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NOTICE
This manual was produced by the Yamaha Motor Company, Ltd. primarily for use by Yamaha deal-
ers and their qualified mechanics. It is not possible to include all the knowledge of a mechanic in
one manual. Therefore, anyone who uses this book to perform maintenance and repairs on Yamaha
vehicles should have a basic understanding of mechanics and the techniques to repair these types
of vehicles. Repair and maintenance work attempted by anyone without this knowledge is likely to
render the vehicle unsafe and unfit for use.
Yamaha Motor Company, Ltd. is continually striving to improve all of its models. Modifications and
significant changes in specifications or procedures will be forwarded to all authorized Yamaha deal-
ers and will appear in future editions of this manual where applicable.
NOTE:
_
Designs and specifications are subject to change without notice.
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IMPORTANT MANUAL INFORMATION
Particularly important information is distinguished in this manual by the following.
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 scooter operator, a bystander or a person checking or repairing the scooter.
A CAUTION indicates special precautions that must be taken to avoid damage
to the scooter.
A NOTE provides key information to make procedures easier or clearer.
WARNING
CAUTION:
NOTE:

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HOW TO USE THIS MANUAL
This manual is intended as a handy, easy-to-read reference book for the mechanic. Comprehensive
explanations of all installation, removal, disassembly, assembly, repair and check procedures are
laid out with the individual steps in sequential order.
1The manual is divided into chapters. An abbreviation and symbol in the upper right corner of
each page indicate the current chapter.
Refer to “SYMBOLS”.
2Each chapter is divided into sections. The current section title is shown at the top of each page,
except in Chapter 3 (“PERIODIC CHECKS AND ADJUSTMENTS”), where the sub-section
title(s) appears.
3Sub-section titles appear in smaller print than the section title.
4To help identify parts and clarify procedure steps, there are exploded diagrams at the start of
each removal and disassembly section.
5Numbers are given in the order of the jobs in the exploded diagram. A circled number indicates a
disassembly step.
6Symbols indicate parts to be lubricated or replaced.
Refer to “SYMBOLS”.
7A job instruction chart accompanies the exploded diagram, providing the order of jobs, names of
parts, notes in jobs, etc.
8Jobs requiring more information (such as special tools and technical data) are described sequen-
tially.

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SYMBOLS
The following symbols are not relevant to
every vehicle.
Symbols 1to 9indicate the subject of each
chapter.
1General information
2Specifications
3Periodic checks and adjustments
4Chassis
5Engine
6Cooling system
7Fuel injection system
8Electrical system
9Troubleshooting
Symbols 0to Gindicate the following.
0Serviceable with engine mounted
AFilling fluid
BLubricant
CSpecial tool
DTightening torque
EWear limit, clearance
FEngine speed
GElectrical data
Symbols Hto Min the exploded diagrams
indicate the types of lubricants and lubrication
points.
HEngine oil
IGear oil
JMolybdenum-disulfide oil
KWheel-bearing grease
LLithium-soap- based grease
MMolybdenum-disulfide grease
Symbols Nto Oin the exploded diagrams
indicate the following.
NApply locking agent (LOCTITE®)
OReplace the part
12
34
56
78
90
AB
CD
EFG
HIJ
KLM
NO
GEN
INFO
SPEC
CHK
ADJ
CHAS
ENG
COOL
FI –+
ELEC
TRBL
SHTG
T
R
.
.
EGM
BLS M
LT
New

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

GEN
INFO 1

GEN
INFO
CHAPTER 1
GENERAL INFORMATION
SCOOTER IDENTIFICATION..........................................................................1-1
VEHICLE IDENTIFICATION NUMBER .....................................................1-1
MODEL LABEL..........................................................................................1-1
FEATURES......................................................................................................1-2
OUTLINE OF FI SYSTEM .........................................................................1-2
FI SYSTEM................................................................................................1-3
INSTRUMENT FUNCTION .......................................................................1-4
IMPORTANT INFORMATION .......................................................................1-10
PREPARATION FOR REMOVAL AND DISASSEMBLY.........................1-10
REPLACEMENT PARTS.........................................................................1-10
GASKETS, OIL SEALS AND O-RINGS ..................................................1-10
LOCK WASHERS/PLATES AND COTTER PINS ...................................1-11
BEARINGS AND OIL SEALS ..................................................................1-11
CIRCLIPS ................................................................................................1-11
CHECKING THE CONNECTIONS ................................................................1-12
SPECIAL TOOLS ..........................................................................................1-13