Read this manual carefully before operating this vehicle. This manual should stay with this vehicle if it is sold.

Il convient de lire attentivement ce manuel avant la première utilisation du véhicule. Le manuel doit être remis

avec le véhicule en cas de vente de ce dernier.

Bitte lesen Sie diese Bedienungsanleitung sorgfältig durch, bevor Sie das Fahrzeug in Betrieb nehmen. Diese

Bedienungsanleitung muss, wenn das Fahrzeug verkauft wird, beim Fahrzeug verbleiben.

Leggere attentamente questo manuale prima di utilizzare il veicolo. Questo manuale dovrebbe accompa-

gnare il veicolo se viene venduto.

YZ125G2

2015

2016

YZ125

1SR-28199-34-E0

OWNER’S SERVICE MANUAL

OWNER’S SERVICE MANUAL

Read this manual carefully before operating this vehicle.

Read this manual carefully before operating this vehicle.

YZ125

YZ125G2

OWNER'S SERVICE MANUAL

©2015 by Yamaha Motor Co., Ltd.

1st Edition, May 2015

All rights reserved.Any reprinting or

unauthorized use without the written

permission of Yamaha Motor Co., Ltd.

is expressly prohibited.

Printed in Japan

FOREWORD

INTRODUCTION

Congratulations on your purchase of

a Yamaha YZ series. This model is

the culmination of Yamaha's vast ex-

perience in the production of paceset-

ting racing machines. It represents

the highest grade of craftsmanship

and reliability that have made Yama-

ha a leader.

This manual explains operation, in-

spection, basic maintenance and tun-

ing of your machine. If you have any

questions about this manual or your

machine, please contact your Yama-

ha dealer.

Yamaha continually seeks advance-

ments in product design and quality.

Therefore, while this manual contains

the most current product information

available at the time of printing, there

may be minor discrepancies between

your machine and this manual. If you

have any questions concerning this

manual, please consult your Yamaha

dealer.

PLEASE READ THIS MANUAL

CAREFULLY AND COMPLETELY

BEFORE OPERATING THIS MA-

CHINE. DO NOT ATTEMPT TO OP-

ERATE THIS MACHINE UNTIL YOU

HAVE ATTAINED A SATISFACTO-

RY KNOWLEDGE OF ITS CON-

TROLS AND OPERATING

FEATURES AND UNTIL YOU HAVE

BEEN TRAINED IN SAFE AND

PROPER RIDING TECHNIQUES.

REGULAR INSPECTIONS AND

CAREFUL MAINTENANCE,

ALONG WITH GOOD RIDING

SKILLS, WILL ENSURE THAT YOU

SAFETY ENJOY THE CAPABILI-

TIES AND THE RELIABILITY OF

THIS MACHINE.

IMPORTANT MANUAL

INFORMATION

Particularly important information is

distinguished in this manual by the

following notations.

This is the safety alert symbol. It is

used to alert you to potential per-

sonal injury hazards. Obey all safe-

ty messages that follow this

symbol to avoid possible injury or

death.

A WARNING indicates a hazardous

situation which, if not avoided,

could result in death or serious in-

jury.

A NOTICE indicates special pre-

cautions that must be taken to

avoid damage to the vehicle or oth-

er property.

A TIP provides key information to

make procedures easier or clearer.

SAFETY INFORMATION

THIS MACHINE IS DESIGNED

STRICTLY FOR COMPETITION

USE, ONLY ON A CLOSED

COURSE. It is illegal for this machine

to be operated on any public street,

road, or highway. Off-road use on

public lands may also be illegal.

Please check local regulations before

riding.

• THIS MACHINE IS TO BE OPER-

ATED BY AN EXPERIENCED RID-

ER ONLY.

Do not attempt to operate this ma-

chine at maximum power until you

are totally familiar with its character-

istics.

• THIS MACHINE IS DESIGNED TO

BE RIDDEN BY THE OPERATOR

ONLY.

Do not carry passengers on this

machine.

• ALWAYS WEAR PROTECTIVE

APPAREL.

When operating this machine, al-

ways wear an approved helmet with

goggles or a face shield. Also wear

heavy boots, gloves, and protective

clothing. Always wear proper fitting

clothing that will not be caught in

any of the moving parts or controls

of the machine.

• ALWAYS MAINTAIN YOUR MA-

CHINE IN PROPER WORKING

ORDER.

For safety and reliability, the ma-

chine must be properly maintained.

Always perform the pre-operation

checks indicated in this manual.

Correcting a mechanical problem

before you ride may prevent an ac-

cident.

GASOLINE IS HIGHLY FLAMMA-

BLE.

Always turn off the engine while re-

fueling. Take care to not spill any

gasoline on the engine or exhaust

system. Never refuel in the vicinity

of an open flame, or while smoking.

• GASOLINE CAN CAUSE INJURY.

If you should swallow some gaso-

line, inhale excess gasoline vapors,

or allow any gasoline to get into

your eyes, contact a doctor immedi-

ately. If any gasoline spills onto

your skin or clothing, immediately

wash skin areas with soap and wa-

ter, and change your clothes.

• ONLY OPERATE THE MACHINE

IN AN AREA WITH ADEQUATE

VENTILATION.

Never start the engine or let it run

for any length of time in an enclosed

area. Exhaust fumes are poison-

ous. These fumes contain carbon

monoxide, which by itself is odor-

less and colorless. Carbon monox-

ide is a dangerous gas which can

cause unconsciousness or can be

lethal.

• PARK THE MACHINE CAREFUL-

LY; TURN OFF THE ENGINE.

Always turn off the engine if you are

going to leave the machine. Do not

park the machine on a slope or soft

ground as it may fall over.

• THE ENGINE, EXHAUST PIPE,

MUFFLER, AND OIL TANK WILL

BE VERY HOT AFTER THE EN-

GINE HAS BEEN RUN.

Be careful not to touch them or to

allow any clothing item to contact

them during inspection or repair.

• PROPERLY SECURE THE MA-

CHINE BEFORE TRANSPORTING

IT.

When transporting the machine in

another vehicle, always be sure it is

properly secured and in an upright

position and that the fuel cock is in

the "OFF" position. Otherwise, fuel

may leak out of the carburetor or

fuel tank.

HOW TO USE THIS MANUAL

FINDING THE REQUIRED PAGE

1. This manual consists of seven

chapters; "General Information",

"Specifications", "Regular inspec-

tion and adjustments", "Engine",

"Chassis", "Electrical" and "Tun-

ing"

2. The table of contents is at the be-

ginning of the manual. Look over

the general layout of the book be-

fore finding then required chapter

and item.

Bend the book at its edge, as

shown, to find the required fore

edge symbol mark and go to a

page for required item and de-

scription.

MANUAL FORMAT

All of the procedures in this manual

are organized in a sequential, step-

by-step format. The information has

been complied to provide the me-

chanic with an easy to read, handy

reference that contains comprehen-

sive explanations of all disassembly,

repair, assembly, and inspection op-

erations.

In this revised format, the condition of

a faulty component will precede an

arrow symbol and the course of ac-

tion required will follow the symbol,

e.g.,

• Bearings

Pitting/damage →Replace.

HOW TO READ DESCRIPTIONS

To help identify parts and clarify pro-

cedure steps, there are exploded dia-

grams at the start of each removal

and disassembly section.

1. An easy-to-see exploded diagram

"1" is provided for removal and

disassembly jobs.

2. Numbers "2" are given in the or-

der of the jobs in the exploded di-

agram. A number that is enclosed

by a circle indicates a disassem-

bly step.

3. An explanation of jobs and notes

is presented in an easy-to-read

way by the use of symbol marks

"3". The meanings of the symbol

marks are given on the next page.

4. A job instruction chart "4" accom-

panies the exploded diagram,

providing the order of jobs, names

of parts, notes in jobs, etc.

5. For jobs requiring more informa-

tion, the step-by-step format sup-

plements "5" are given in addition

to the exploded diagram and job

instruction chart.

ILLUSTRATED SYMBOLS (Refer to

the illustration)

Illustrated symbols "1" to "7" are used

to identify the specifications appear-

ing in the text.

1.

With engine mounted

2.

Filling fluid

3.

Lubricant

4.

Special tool

5.

Tightening

6.

Specified value, Service limit

7.

Resistance (Ω), Voltage (V),

Electric current (A)

Illustrated symbols "8" to "14" in the

exploded diagrams indicate grade of

lubricant and location of lubrication

point.

8.

Apply engine mixing oil

9.

Apply transmission oil

10.

Apply molybdenum disulfide oil

11.

Apply brake fluid

12.

Apply lightweight lithium-soap

base grease

13.

Apply molybdenum disulfide

grease

14.

Apply silicone grease

Illustrated symbols "15" to "16" in the

exploded diagrams indicate where to

apply a locking agent and where to in-

stall new parts.

15.

Apply locking agent (LOC-

TITE^®)

16.

Use new one

1

2

3

4

5

TABLE OF CONTENTS

GENERAL INFORMATION

1

SPECIFICATIONS

2

REGULAR INSPECTION AND

ADJUSTMENTS

3

ENGINE

4

CHASSIS

5

ELECTRICAL

6

TUNING

7

CONTENTS

CHAPTER 1

GENERAL

INFORMATION

LOCATION OF

IMPORTANT LABELS ..... 1-1

DESCRIPTION ................. 1-5

CONSUMER

INFORMATION................. 1-6

INCLUDED PARTS .......... 1-6

IMPORTANT

INFORMATION................. 1-6

CHECKING OF

CONNECTION.................. 1-7

SPECIAL TOOLS............. 1-8

CONTROL

FUNCTIONS................... 1-11

STARTING AND

BREAK-IN ...................... 1-11

TORQUE-CHECK

POINTS........................... 1-13

MAINTENANCE AFTER

BREAK-IN ...................... 1-14

CLEANING AND

STORAGE ...................... 1-14

CHAPTER 2

SPECIFICATIONS

GENERAL

SPECIFICATIONS............ 2-1

MAINTENANCE

SPECIFICATIONS............ 2-3

TIGHTENING

TORQUES ........................ 2-8

CABLE ROUTING

DIAGRAM....................... 2-14

CHAPTER 3

REGULAR

INSPECTION AND

ADJUSTMENTS

MAINTENANCE

INTERVALS......................3-1

PRE-OPERATION

INSPECTION AND

MAINTENANCE................3-5

ENGINE ............................3-6

CHASSIS ........................3-10

ELECTRICAL .................3-20

CHAPTER 4

ENGINE

SEAT, FUEL TANK AND

SIDE COVERS..................4-1

EXHAUST PIPE AND

SILENCER........................4-3

RADIATOR .......................4-5

CARBURETOR AND

REED VALVE ...................4-7

CYLINDER HEAD,

CYLINDER AND

PISTON...........................4-12

CLUTCH .........................4-19

KICK SHAFT AND

SHIFT SHAFT.................4-23

YPVS GOVERNOR.........4-28

WATER PUMP................4-30

CDI MAGNETO...............4-33

ENGINE REMOVAL .......4-35

CRANKCASE AND

CRANKSHAFT ...............4-39

TRANSMISSION,

SHIFT CAM AND

SHIFT FORK...................4-44

CHAPTER 5

CHASSIS

FRONT WHEEL AND

REAR WHEEL ..................5-1

FRONT BRAKE AND

REAR BRAKE ..................5-6

FRONT FORK.................5-16

HANDLEBAR..................5-24

STEERING ......................5-29

SWINGARM ....................5-32

REAR SHOCK

ABSORBER....................5-37

CHAPTER 6

ELECTRICAL

ELECTRICAL

COMPONENTS AND

WIRING DIAGRAM...........6-1

IGNITION SYSTEM...........6-2

CHAPTER 7

TUNING

ENGINE.............................7-1

CHASSIS ..........................7-6

1-1

LOCATION OF IMPORTANT LABELS

GENERAL INFORMATION

LOCATION OF IMPORTANT LABELS

Please read the following important labels carefully before operating this vehicle.

CANADA

1

1-2

LOCATION OF IMPORTANT LABELS

EUROPE

1-3

LOCATION OF IMPORTANT LABELS

AUS, NZ, ZA

1-4

LOCATION OF IMPORTANT LABELS

Familiarize yourself with the following pictograms and read the explanatory text.

Read Owner's service manual.

This unit contains high-pressure nitrogen gas. Mishandling can cause explosion. Do not incinerate,

puncture or open.

Turn off the main switch after riding to avoid draining the battery.

Use unleaded gasoline only.

Measure tire pressure when tires are cold.

Adjust tire pressure.

Improper tire pressure can cause loss of control.

Loss of control can result in severe injury or death.

1-5

DESCRIPTION

DESCRIPTION

• The machine you have purchased may differ slightly from those shown in the following.

• Designs and specifications are subject to change without notice.

1.

Clutch lever

2.

Engine stop switch

3.

Front brake lever

4.

Throttle grip

5.

Radiator cap

6.

Fuel tank cap

7.

Kickstarter lever

8.

Fuel tank

9.

Radiator

10.

Coolant drain bolt

11.

Check bolt (Transmission oil level)

12.

Rear brake pedal

13.

Valve joint

14.

Fuel cock

15.

Air filter

16.

Drive chain

17.

Shift pedal

18.

Starter knob

19.

Front fork