Yamaha SR125'99 3MW-AE3 User manual

FOREWORD
This Supplementary Service Manual has been prepared to introduce new service and data for the
SR125 ’99. For complete service information procedures it is necessary to use this Supplementary
Service Manual together with the following manual.
SR125 SERVICE MANUAL: 3MW-AE1
SR125 SUPPLEMENTARY SERVICE MANUAL: 3MW-AE2
SR125 ’99
SUPPLEMENTARY
SERVICE MANUAL
1998 by Yamaha Motor Co., Ltd.
First Edition, October 1998
Any reproduction or unauthorized use
without the written permission of
Yamaha Motor Co., Ltd. is expressly
prohibited.

NOTE:
CAUTION:
EB001000
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-
torcycleshasabasicunderstandingofthemechanicalideasandtheproceduresofmotorcyclerepair.
Repairs attempted by anyone without this knowledge are likely to render the motorcycle unsafe and
unfit for use.
YamahaMotorCompany,Ltd.iscontinuallystrivingtoimproveallitsmodels.Modificationsandsignifi-
cant 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.
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!
Failuretofollow WARNINGinstructionscouldresult insevereinjuryordeathto
thescooteroperator,abystanderoraperson inspecting orrepairingthescoot-
er.
ACAUTIONindicatesspecialprecautionsthatmustbe taken to avoid damage
to the scooter.
NOTE: A NOTE provides key information to make procedures easier or clearer.

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YP002000 HOW TO USE THIS MANUAL
MANUAL ORGANIZATION
This manual consists of chapters for the main categories of subjects. (See “Illustrated symbols”)
1st title 1: This is the title of the chapter with its symbol on 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
Tohepsidentifypartsandclarifyproceduresteps,thereareexplodeddiagramsatstartofeachremov-
al and disassembly section.
1. An easy-to-see exploded diagram 4is provided for disassembly and assembly jobs.
2. Numbers 5are given in the order of 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. Ajob instructionchart 7accompaniestheexplodeddiagram,providingthe orderofjobs,namesof
parts, notes in jobs, etc.
5. Forjobsrequiring more information, the step-by-step formatsupplements8 are given in addition to
the exploded diagram and the job instruction chart.

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24 25
2321
19 2018
16 1715
1413
11 12
10
GEN
INFO SPEC
ENG
CARB
ELECCHAS
COOL
INSP
ADJ
TRBL
SHTG
EB003000
ILLUSTRATED SYMBOLS
Illustrated symbols 1to 9are designed as
thumb tabs to indicate the chapter’s number
and content.
1General information
2Specifications
3Periodic inspection and adjustment
4Engine
5Cooling system
6Carburetion
7Chassis
8Electrical
9Troubleshooting
Illustrated symbols 10 to 17 are used to identify the
specifications appearing in the text.
10 Possible to maintain with engine mounted
11 Filling fluid
12 Lubricant
13 Special tool
14 Tightening
15 Wear limit, clearance
16 Engine speed
17 Ω, V, A
Illustratedsymbols 18 to 23 intheexplodeddia-
grams indicate the types of lubricants and lu-
brication points.
18 Apply engine oil
19 Apply gear oil
20 Apply molybdenum disulfide oil
21 Apply wheel bearing grease
22 Apply lightweight lithium-soap base grease
23 Apply molybdenum disulfide grease
Illustratedsymbols 24 to 25 intheexplodeddia-
gramsindicatethewheretoapplylockingagent
24 and when to install new parts 25 .
24 Apply locking agent (LOCTITE)
25 Use new one

CONTENTS
GENERAL SPECIFICATIONS
GENERAL SPECIFICATIONS 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MAINTENANCE SPECIFICATIONS 2. . . . . . . . . . . . . . . . . . . . . . . . . . .
ENGINE 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CHASSIS 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ELECTRICAL 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TIGHTENING TORQUES 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ENGINE 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CHASSIS 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CABLE ROUTING 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PERIODIC INSPECTIONS AND ADJUSTMENTS
CHECKING AND ADJUSTING THE STEERING HEAD 9. . . . . . . . . . . . .
CHECKING AND ADJUSTING THE STEERING HEAD 9. . . . . . . . .
ENGINE OVERHAUL
CYLINDER HEAD 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CYLINDER HEAD 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CHECKING THE TIMING CHAIN TENSIONER 12. . . . . . . . . . . . . . . .
CYLINDER HEAD INSTALLATION 12. . . . . . . . . . . . . . . . . . . . . . . . . . .
CHASSIS
STEERING 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
UNDER BRACKET 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
’99 SR125 WIRING DIAGRAM

–1–
GENERAL SPECIFICATIONS SPEC
SPECIFICATIONS
GENERAL SPECIFICATIONS
Model SR125
Model code: 3MW8
Dimensions:
Overall height 1,100 mm
Chassis:
Caster angle
Trail 26.75
90 mm
Wheel travel:
Rear wheel travel 76 mm
Bulb wattage quantity:
Headlight
Auxiliary light
Tail/brake light
Flasher light
Meter light
High beam indicator
Neutral indicator
Turn indicator
12 V 60 W/55 W 1
12 V 4 W 1
12 V 5 W/21 W 1
12 V 21 W 4
14 V 3 W 1
12 V 1.7 W 1
12 V 1.7 W 1
12 V 1.7 W 1

–2–
MAINTENANCE SPECIFICATIONS SPEC
MAINTENANCE SPECIFICATIONS
ENGINE
Item Standard Limit
Cam chain:
Cam chain type/No. of links
Cam chain adjustment DID 25SH/104 ENDLESS
Automatic
SSS
SSS
Carburetor:
Engine idle speed 1,300 – 1,400 rpm SSS
CHASSIS
Item Standard Limit
Steering system:
Steering bearing type Angular bearing SSS
Front suspension:
Fork spring free length
Fitting length
Oil capacity
Oil level
Oil grade
353.4 mm
338.4 mm
0.187 L (187 cm3)
138 mm
Fork oil 10 W or equivalent
321 mm
SSS
SSS
SSS
SSS
ELECTRICAL
Item Standard Limit
Ignition coil:
Primary winding resistance
Secondary winding resistance 0.184 – 0.276 Ωat 20_C
6.32 – 9.48 kΩat 20_C
SSS
SSS
Flasher relay:
Type
Model/manufacturer
Flasher frequency
Full transistor type
FE246BH/DENSO
75 – 95 cycle/min
SSS
SSS
SSS