Yamaha TW125 1999 User manual

EAS00000
TW125
SERVICE MANUAL
1998 by Yamaha Motor Co., Ltd.
1st Edition, July 1998
All rights reserved. Any reprinting or
unauthorized use without the written
permission of Yamaha Motor Co., Ltd.
is expressly prohibited.

NOTE:
WARNING
CAUTION:
EAS00002 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 mo-
torcycle has a basic understanding of the mechanical ideas and the procedures of motorcycle repair.
Repairs attempted by anyone without this knowledge are likely to render the motorcycle unsafe and
unfit for use.
YamahaMotorCompany,Ltd.,iscontinuallystrivingtoimproveallitsmodels.Modificationsandsignif-
icant changes in specifications or procedures will be forwarded to all authorized Yamaha dealers and
will appear in future editions of this manual where applicable.
Designs and specifications are subject to change without notice.
EAS00004
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!
FailuretofollowWARNINGinstructionscouldresultinsevereinjuryor
deathtothemotorcycleoperator,abystanderorapersoninspectingor
repairing the motorcycle.
A CAUTION indicates special precautions that must be taken to avoid
damage to the motorcycle.
NOTE: A NOTE provides key information to make procedures easier or clearer.

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2
5
7
6
43
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EAS00007 HOW TO USE THIS MANUAL
This manual is intended as a handy, easy-to-read reference book for the mechanic. Comprehensive
explanationsofallinstallation,removal,disassembly,assembly, repair and inspection proceduresare
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” on the following page.
2Each chapter is divided into sections. The current section title is shown at the top of each page,
except in Chapter 3 (“Periodic Inspections and Adjustments”), where the sub-section title(-s) appear.
(InChapter 3, “Periodic Inspections and Adjustments”, the sub-section title appears atthe topof each
page, instead of the section title.)
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 (see “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.

21
1
3
5
7
9
2
4
8
6
23 24
2220
18 1917
15
1413
11 12
10
GEN
INFO SPEC
ENG
CARB
ELEC
CHAS
CHK
ADJ
TRBL
SHTG
16
EAS00009
SYMBOLS
The following symbols are not relevant to every
vehicle.
Symbols 1to 9indicate the subject of each
chapter.
1General information
2Specifications
3Periodic inspections and adjustments
4Engine
5Carburetor(-s)
6Chassis
7Electrical system
8Troubleshooting
Symbols 9to 16 indicate the following.
9Serviceable with engine mounted
10 Filling fluid
11 Lubricant
12 Special tool
13 Tightening torque
14 Wear limit, clearance
15 Engine speed
16 Electrical data
Symbols 17 to 22 intheexplodeddiagramsindi-
cate the types of lubricants and lubrication
points.
17 Engine oil
18 Gear oil
19 Molybdenum disulfide oil
20 Wheel bearing grease
21 Lithium soap base grease
22 Molybdenum disulfide grease
Symbols 23 to 24 intheexplodeddiagramsindi-
cate the following:
23 Apply locking agent (LOCTITE)
24 Replace the part

GENERAL INFORMATION
SPECIFICATIONS
PERIODIC INSPECTION AND
ADJUSTMENT
ENGINE OVERHAUL
CARBURATION
CHASSIS
ELECTRICAL
TROUBLESHOOTING
GEN
INFO 1
SPEC 2
3
ENG 4
CARB 5
CHAS 6
ELEC 7
TRBL
SHTG 8
CHK
ADJ
INDEX

GEN
INFO
1

CHAPTER 1.
GENERAL INFORMATION
MOTORCYCLE IDENTIFICATION 1–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
VEHICLE IDENTIFICATION NUMBER 1–1. . . . . . . . . . . . . . . . . . . . . . . . .
MODEL CODE 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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1
MOTORCYCLE IDENTIFICATION GEN
INFO
EAS00014
GENERAL INFORMATION
MOTORCYCLE IDENTIFICATION
EAS00017
VEHICLE IDENTIFICATION NUMBER
Thevehicleidentificationnumber 1isstamped
into the right side of the steering head.
EAS00018
MODEL CODE
The model code label 1is affixed to the frame.
This information will be needed to order spare
parts.

1-2
IMPORTANT INFORMATION GEN
INFO
EAS00020
IMPORTANT INFORMATION
PREPARATION FOR REMOVAL AND DIS-
ASSEMBLY
1. Beforeremovalanddisassembly,removeall
dirt, mud, dust and foreign material.
2. Use only the proper tools and cleaning
equipment.
Refer to the “SPECIAL TOOLS” section.
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
mustalwaysbereusedor replacedasanas-
sembly.
4. During disassembly, clean all of the parts
and place them in trays in the order of disas-
sembly. This will speed up assembly and al-
low for the correct installation of all parts.
5. Keep all parts away from any source of fire.
EAS00021
REPLACEMENT PARTS
1. Use only genuine Yamaha parts for all re-
placements. 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.
EAS00022
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 apply grease onto
the oil seal lips.

1-3
IMPORTANT INFORMATION GEN
INFO
OR
CAUTION:
EAS00023
LOCK WASHERS/PLATES AND COTTER
PINS
1. After removal, replace all lock wash-
ers/plates
1andcotterpins.Aftertheboltor
nuthasbeentightenedtospecification,bend
the lock tabs along a flat of the bolt or nut.
EAS00024
BEARINGS AND OIL SEALS
1. Install bearings and oil seals so that the
manufacturer’s marks or numbers are vis-
ible. When installing oil seals, apply a light
coat of lithium soap base grease onto the oil
seal lips. Oil bearings liberally when instal-
ling, if appropriate.
1Oil seal
Donotspin thebearingwithcompressed air
because this will damage the bearing sur-
faces.
1Bearing
EAS00025
CIRCLIPS
1. Beforereassembly,checkallcirclipscareful-
ly and replace damaged or distorted circlips.
Alwaysreplacepistonpinclipsafteroneuse.
When installing a circlip 1, make sure that
the sharp-edged corner 2is positioned op-
posite the thrust 3that the circlip receives.
4Shaft

1-4
CHECKING THE CONNECTIONS GEN
INFO
NOTE:
NOTE:
NOTE:
EAS00026
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.
If the pin 1on the terminal is flattened, bend it
up.
4. Connect:
lead
coupler
connector
Make sure that all connections are tight.
5. Check:
continuity
(with a pocket tester)
Pocket tester
90890-03112
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.

1-5
SPECIAL TOOLS GEN
INFO
EAS00020
SPECIAL TOOLS
The following special tools are necessary for complete and accurate tune-up and assembly. Use only
theappropriatespecialtools;this willhelppreventdamagecausedbytheuseof inappropriate toolsor
improvised techniques.
When placing an order, refer to the list provided below to avoid any mistakes.
Tool No. Tool name/Usage Illustration
90890-01080
90890-04052 Rotor puller Attachment
These tools are used when removing the
generator rotor.
90890-01083
90890-01084 Rocker arm shaft puller bolt Weight
These tools are used when removing or
installing the rocker arm shafts.
90890-01268 Ringnut wrench
This tool is used to loosen and tighten the ex-
haust and steering ringnut.
90890-01294
90890-01326 Damper rod holder T-handle
This tool is used for disassembling or assem-
bling the front fork
90890-01311 Valve adjusting tool
This tool is necessary for adjusting valve
clearance.
90890-01312 Fuel level gauge
This gauge is used to measure the fuel level
in the float chamber.
90890-01367
90890-01368 Fork seal driver weight Fork seal driver attachment (ø33 mm)
This tool is used when installing the fork seal.
90890-01403 Ring nut wrench
This tool is used to loosen and tighten the
steering ring nut.
90890-01701 Sheave holder
This tool is used for holding the generator
rotor

1-6
SPECIAL TOOLS GEN
INFO
Tool No. Tool name/Usage Illustration
90890-03079 Thickness gauge
This tool is used to measure the valve
clearance.
90890-03081
90890-04082 Compression gauge Adaptor
These tools are used to measure the engine
compression.
90890-03112 Pocket tester
These instruments are invaluable for
checking the electrical system.
90890-03113 Engine tachometer
This tool is needed for detecting engine rpm.
90890-03141 Timing light
This tool is necessary for checking ignition
timing.
90890-04019
90890-04108 Valve spring compressor Attachment
These tools are used when removing or
installing the valve and the valve spring.
90890-04064 Valve guide remover 6 mm
This tool is used to remove the valve guide.
90890-04065 Valve guide reamer 6 mm
This tool is used to rebore the valve guide.
90890-04066 Valve guide installer 6 mm
This tool is needed to install the valve guides
properly.
90890-04086 Clutch holding tool
This tool is used for holding the clutch boss.

1-7
SPECIAL TOOLS GEN
INFO
Tool No. Tool name/Usage Illustration
90890-04101 Valve lapper
This tool is used for lapping the valve.
90890-06754 Ignition checker
This instrument is necessary for checking the
ignition system components.
90890-85505 Yamaha bond No.1215
This sealant (bond) is used for crankcase
mating surface, etc.

GEN
INFO

SPEC
2