Yamaha SR125 98 Manual

FOREWORD
This Supplementary Service Manual has been prepared to introduce new service and data for the
SR125’98.Forcompleteinformationonserviceprocedures,itisnecessarytousethisSupplementary
Service Manual together with following manual:
SR125 ’97 SERVICE MANUAL: 3MW-AE1
SR125 ’98
SUPPLEMENTARY
SERVICE MANUAL
1997 by Yamaha Motor Co., Ltd.
1st Edition July 1997
All rights reserved. Any reprinting 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-
torcycleshas abasic understandingof themechanical ideasand theprocedures ofmotorcycle repair.
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!
FailuretofollowWARNINGinstructionscouldresultinsevereinjuryor deathto
the motorcycle operator, a bystander or a person inspecting or repairing the
motorcycle.
ACAUTION indicatesspecial precautionsthatmustbetaken toavoid damage
to the motorcycle.
NOTE: A NOTE provides key information to make procedures easier or clearer.

1
2
6
7
6
43
8
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HOW TO USE THIS MANUAL
CONSTRUCTION OF THIS MANUAL
This manual consists of chapters for the main categories of subjects. (See “Illustrated symbols”)
1st title 1: This is a chapter with its symbol on the upper right of each page.
2nd title 2: This title appears on the upper of each page on the left of the chapter symbol.
(For the chapter “Periodic inspection and adjustment” the 3rd title appears.)
3rd title 3: This is a final title.
MANUAL FORMAT
Alloftheproceduresinthismanualareorganizedinasequential,step-by-stepformat.Theinformation
has been compiled to provide the mechanic with an easy to read, handy reference that contains com-
prehensive explanations of all disassembly, repair, assemblyand inspections. A set of particularlyim-
portant procedure ( 4) is placed between aline of asterisks (*); with each procedure preceded by ().
IMPORTANT FEATURES
Data and a special tool are framed in a box preceded by a relevant symbol (5).
Anencirclednumeral( 6)indicatesapartname,andanencircledalphabeticalletterdataoranalign-
ment mark (7), the others being indicated by an alphabetical letter in a box (8).
A condition of a faulty component will precede an arrow symbol and course of action required the
symbol ( 9).
EXPLODED DIAGRAM
Eachchapterprovidesexplodeddiagramsbeforeeachdisassemblysectionforeaseinidentifyingcor-
rect disassembly and assembly procedures.

21
1
3
5
7
9
2
4
8
6
23 24
2220
18 1917
1615
1413
11 12
10
GEN
INFO SPEC
ENG
CARB
ELEC
CHAS
INSP
ADJ
TRBL
SHTG
EB003000
ILLUSTRATED SYMBOLS
Illustrated symbols 1to 8are designed as
thumb tabs to indicate the chapter’s number
and content.
1General information
2Specifications
3Periodic inspection and adjustment
4Engine
5Carburation
6Chassis
7Electrical
8Troubleshooting
Illustrated symbols 9to 16 are used to identify
the specifications appearing in the text.
9Possible to maintain with engine mounted
10 Filling fluid
11 Lubricant
12 Special tool
13 Tightening
14 Wear limit, clearance
15 Engine speed
16 Ω, V, A
Illustratedsymbols 17 to 22 in theexplodeddia-
grams indicate the types of lubricants and lu-
brication points.
17 Apply engine oil
18 Apply gear oil
19 Apply molybdenum disulfide oil
20 Apply wheel bearing grease
21 Apply lightweight lithium-soap base grease
22 Apply molybdenum disulfide grease
Illustratedsymbols 23 to 24 in theexplodeddia-
gramsindicatethewheretoapplylockingagent
23 and when to install new parts 24 .
23 Apply locking agent (LOCTITE)
24 Use new one

CONTENTS
GENERAL INFORMATION 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MOTORCYCLE IDENTIFICATION 1. . . . . . . . . . . . . . . . . . . . . . . . . . . .
FRAME SERIAL NUMBER 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ENGINE SERIAL NUMBER 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MODEL LABEL 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SPECIFICATIONS 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GENERAL SPECIFICATIONS 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MAINTENANCE SPECIFICATIONS 2. . . . . . . . . . . . . . . . . . . . . . . . . . .
CHASSIS 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ELECTRICAL 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PERIODIC INSPECTIONS AND ADJUSTMENT 3. . . . . . . . . . . . . . . . . . .
INTRODUCTION 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PERIODIC MAINTENANCE/LUBRICATION INTERVALS 3. . . . . . . .

–1–
MOTORCYCLE IDENTIFICATION GEN
INFO
NOTE:
YP100000
GENERAL INFORMATION
MOTORCYCLE IDENTIFICATION
SR100020
FRAME SERIAL NUMBER
The frame serial number 1is stamped into the
right side of the frame.
EB100030
ENGINE SERIAL NUMBER
Theengineserialnumber 1isstampedintothe
crankcase.
Designs and specifications are subject to
change without notice.
MODEL LABEL
The model label 1is affixed under the seat.
This information will be needed to order spare
parts.

–2–
GENERAL SPECIFICATIONS/
MAINTENANCE SPECIFICATIONS SPEC
SPECIFICATIONS
GENERAL SPECIFICATIONS
Model SR125
Model code: 3MW7
Dimensions:
Overall length
Wheelbase 2,020 mm
1,285 mm
Chassis:
Caster angle
Trail 27
95 mm
Electrical:
Generator system C.D.I. magneto
Bulb wattage quantity:
Headlight 12 V 35 W/35 W 1
MAINTENANCE SPECIFICATIONS
CHASSIS Item Standard Limit
Front suspension:
Oil capacity
Oil level 0.184 L (184 cm3)
140 mm (Full stroke) 

ELECTRICAL
Item Standard Limit
Ignition coil:
Primary winding resistance
Secondary winding resistance 0.184 0.276 Ωat 20C
5.68 8.52 kΩat 20C

Charging system:
Type C.D.I. magneto 
Electric starter system:
Armature coil resistance
Brash spring pressure 0.0017 0.0027 Ωat 20C
8.33 N 

Starter relay:
Model/manufacturer MS5E-661/JIDECO 
Flasher relay:
Model/manufacturer
Flasher frequency FZ264BH/DENSO
76.5 93.5 cycle/min 


–3–
INTRODUCTION/PERIODIC
MAINTENANCE/LUBRICATION INTERVALS INSP
ADJ
10.
11.
12.
13.
14.
EB300000 PERIODIC INSPECTIONS AND ADJUSTMENTS
INTRODUCTION
This chapter includes all information necessary to perform recommended inspections and adjust-
ments.Thesepreventivemaintenanceprocedures,itfollowed,willensuremorereliablevehicleopera-
tion and a longer service life. The need for costly overhaul work will be greatly reduced. This informa-
tionappliestovehiclesalreadyinserviceaswellastonewvehiclesthatarebeingpreparedforsale.All
service technicians should be familiar with this entire chapter.
YP301000
PERIODIC MAINTENANCE/LUBRICATION INTERVALS
EVERY
NO. ITEM ROUTINE BRAKE-IN
1,000 KM 6,000 km
or
6 months
12,000 km
or
12 months
1. *Fuel line Check fuel hoses for cracks or damage.
Replace if necessary.  
2. Spark plug Check condition.
Clean, regap or replace if necessary.   
3. * Valves Check valve clearance.
Adjust if necessary.   
4. * Cam chain Check chain tension.
Adjust if necessary.   
5. * Air filter Clean or replace if necessary.  
6. * Battery
Check electrolyte level and specific gravity.
Correct or recharge if necessary.
Make sure that the breather hose is properly
routed.
 
7. Clutch Check operation.
Adjust or replace cable.  
8. * Front brake Check operation, fluid level and fluid leakage.
Correct accordingly.
Replace brake pads if necessary.  
9. * Rear brake Check operation.
Adjust cable and replace brake shoes if
necessary. Rebalance or replace if necessary.  
* Wheels
Check balance, runout, spoke tightness and for
damage.
Tighten spokes and rebalance, replace if
necessary.
 
* Tires Check tread depth and for damage.
Replace if necessary. Check air pressure.
Correct if necessary.  
* Wheel bearings Check bearing for looseness or damage.
Replace if necessary.  
*Swingarm Check swingarm pivoting point for play.
Correct if necessary.  
Drive chain Check chain slack. Adjust if necessary.
Make sure that the rear wheel is properly
aligned. Clean and lubricate. Every 500 km
*: It is recommended that these items be serviced by a Yamaha dealer.

–4–
PERIODIC MAINTENANCE/LUBRICATION INTERVALS INSP
ADJ
18.
19.
20.
21.
15.
16.
17.
22.
23.
NOTE:
EVERY
NO. ITEM ROUTINE BRAKE-IN
1,000 KM 6,000 km
or
6 months
12,000 km
or
12 months
*Steering bearings
Check bearing play and steering for roughness.
Correct accordingly.
Lubricate with lithium soap base grease every
24,000 km or 24 months (whichever comes first).
 
*Chassis
fasteners Make sure that all nuts, bolts and screws are properly tightened. Tighten if necessary.   
Sidestand/
centerstand Check operation. Lubricate and repair if necessary.   
*Sidestand switch Check operation. Replace if necessary.
Check operation and for oil leakage.   
*Front fork Correct accordingly.
Replace shock absorber assembly if necessary.  
*Rear shock
absorber
assemblies
Check operation and shock absorbers for oil
leakage
Replace shock absorber assembly if necessary.  
* Carburetor Check engine idling speed and starter
operation. Adjust if necessary.
Check oil level and oil leakage.   
Engine oil Correct if necessary.
Change. (Warm engine before draining.)   
Engine oil
filter element Clean or replace if necessary.  
*: It is recommended that these items be serviced by a Yamaha dealer.
Brake fluid replacement:
1. Whendisassemblingthemastercylinderorcalipercylinder,replacethebrakefluid.Normallycheck
the brake fluid level and fill the fluid as required.
2. On the inner parts of the master cylinder and caliper cylinder, replace the oil seals every two years.
3. Replace the brake hoses every four years, or if cracked or damaged.