Yamaha YBR125ED 2005 User manual

2005
YBR125ED
3D9-F8197-E0
SERVICE MANUAL

EAS00000
YBR125ED 2005
SERVICE MANUAL
©2005 by Yamaha Motor Co., Ltd.
First edition, January 2005
All rights reserved.
Any reproduction or unauthorized use
without the written permission of
Yamaha Motor Co., Ltd.
is expressly prohibited.

EAS00002
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.
EAS00004
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 vehicle operator, a bystander or a person checking or repairing the vehicle.
A CAUTION indicates special precautions that must be taken to avoid damage
to the vehicle.
A NOTE provides key information to make procedures easier or clearer.
WARNING
CAUTION:
NOTE:

EAS00007
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.

EAS00009
SYMBOLS
The following symbols are not relevant to
every vehicle. Symbols 1to 8indicate the
subject of each chapter.
1General information
2Specifications
3Periodic checks and adjustments
4Chassis
5Engine
6Carburetor
7Electrical system
8Troubleshooting
Symbols 9to Findicate the following.
9Serviceable with engine mounted
0Filling fluid
ALubricant
BSpecial tool
CTightening torque
DWear limit, clearance
EEngine speed
FElectrical data
Symbols Gto Lin the exploded diagrams
indicate the types of lubricants and lubrication
points.
GEngine oil
HGear oil
IMolybdenum-disulfide oil
JWheel-bearing grease
KLithium-soap-based grease
LMolybdenum-disulfide grease
Symbols Mto Nin the exploded diagrams
indicate the following.
MApply locking agent (LOCTITE®)
NReplace the part
12
34
56
78
90
AB
CD
EF
GHI
JKL
MN
GEN
INFO
SPEC
CHK
ADJ
CHAS
ENG
CARB
–+
ELEC TRBL
SHTG
T
R
.
.
EGM
BLS M
LT
New

EAS00011
TABLE OF CONTENTS
GENERAL INFORMATION GEN
INFO 1
SPECIFICATIONS SPEC 2
PERIODIC CHECKS AND
ADJUSTMENTS CHK
ADJ 3
CHASSIS CHAS 4
ENGINE ENG 5
CARBURETOR CARB 6
ELECTRICAL SYSTEM ELEC 7
TROUBLESHOOTING TRBL
SHTG 8
–+

GEN
INFO
CHAPTER 1
GENERAL INFORMATION
VEHICLE IDENTIFICATION............................................................................1-1
VEHICLE IDENTIFICATION NUMBER .....................................................1-1
MODEL LABEL..........................................................................................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
GEN
INFO
EAS00014
GENERAL INFORMATION
VEHICLE IDENTIFICATION
EAS00017
VEHICLE IDENTIFICATION NUMBER
The vehicle identification number 1is
stamped into the right side of the steering head
pipe.
1
EAS00018
MODEL LABEL
The model label 1is affixed to the frame. This
information will be needed to order spare
parts.
1
VEHICLE IDENTIFICATION

1 - 2
GEN
INFO
IMPORTANT INFORMATION
EAS00020
IMPORTANT INFORMATION
PREPARATION FOR REMOVAL AND
DISASSEMBLY
1. Before removal and disassembly, remove all
dirt, mud, dust and foreign material.
2. Use only the proper tools and cleaning
equipment.
Refer to the “SPECIAL TOOLS”.
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
must always be reused or replaced as an
assembly.
4. During disassembly, clean all of the parts
and place them in trays in the order of dis-
assembly. This will speed up assembly and
allow for the correct installation of all parts.
5. Keep all parts away from any source of fire.
EAS00021
REPLACEMENT PARTS
Use only genuine Yamaha parts for all
replacements. 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 lubricate the oil seal
lips with grease.

1 - 3
GEN
INFO
IMPORTANT INFORMATION
EAS00023
LOCK WASHERS/PLATES AND COTTER
PINS
After removal, replace all lock washers/plates
1and cotter pins. After the bolt or nut has
been tightened to specification, bend the lock
tabs along a flat of the bolt or nut.
EAS00024
BEARINGS AND OIL SEALS
Install bearings and oil seals so that the manu-
facturer’s marks or numbers are visible. When
installing oil seals, lubricate the oil seal lips
with a light coat of lithium-soap-based grease.
Oil bearings liberally when installing, if appro-
priate.
1Oil seal
CAUTION:
_
Do not spin the bearing with compressed
air because this will damage the bearing
surfaces.
1Bearing
EAS00025
CIRCLIPS
Before reassembly, check all circlips carefully
and replace damaged or distorted circlips.
Always replace piston pin clips after one use.
When installing a circlip 1, make sure the
sharp-edged corner 2is positioned opposite
the thrust 3that the circlip receives.
4Shaft

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

1 - 5
GEN
INFO
SPECIAL TOOLS
EAS00027
SPECIAL TOOLS
The following special tools are necessary for complete and accurate tune-up and assembly. Use
only the appropriate special tools as this will help prevent damage caused by the use of inappropri-
ate tools or improvised techniques. Special tools, part numbers or both may differ depending on the
country.
When placing an order, refer to the list provided below to avoid any mistakes.
NOTE:
•For U.S.A. and Canada, use part number starting with “YM-”, “YU-”, or “ACC-”.
•For others, use part number starting with “90890-”.
Tool No. Tool name/Function Illustration
Slide hammer bolt
90890-01083
YU-01083-1
Weight
90890-01084
YU-01083-3
Slide hammer bolt
Weight
These tools are used to remove or install
the rocker arm shafts.
90890-01135
YU-01135-B
Crankcase separating tool
This tool is used to remove the crank-
shaft.
90890-04019
YM-04019
Valve spring compressor
This tool is used to remove or install the
valve assemblies.
Pot
90890-01274
YU-90058
YU-90059
Bolt
90890-01275
YU-90060
Crankshaft installer pot
Crankshaft installer bolt
These tools are used to install the crank-
shaft.
Adapter
90890-01278
YU-90063
Spacer
90890-04081
YM-91044
Adapter (M12)
Spacer (crankshaft installer)
These tools are used to install the crank-
shaft.
90890-01304
YU-01304
Piston pin puller set
This tool is used to remove the piston pin.

1 - 6
GEN
INFO
SPECIAL TOOLS
90890-01311
YM-08035-A
Tappet adjusting tool
This tool is used to adjust the valve clear-
ance.
90890-01312
YM-01312-A
Fuel level gauge
This gauge is used to measure the fuel
level in the float chamber.
90890-01326
YM-01326
T-handle
This tool is used to hold the 14 mm hexa-
gon nut/socket wrench when removing or
installing the damper rod.
90890-01362
YU-33270-B
Flywheel puller
This tool is used to remove the generator
rotor.
Weight
90890-01367
YM-A9409-7
YM-A5142-4
Attachment
90890-01400
Fork seal driver weight
Fork seal driver attachment (ø30)
These tools are used to install the oil
seal, dust seal, and the outer tube bush-
ing of the front fork legs.
90890-01403
YU-33975
Steering nut wrench
This tool is used to loosen or tighten the
steering ring nuts.
90890-01701
YS-01880-A
Sheave holder
This tool is used to hold the A.C. magneto
rotor when loosening or tightening the
A.C. magneto rotor nut.
90890-03079
YM-34483
Thickness gauge
This tool is used to measure the valve
clearance.
Tool No. Tool name/Function Illustration

1 - 7
GEN
INFO
SPECIAL TOOLS
90890-03081
YU-33223
Compression gauge
These tools are used to measure the
engine compression.
90890-03112
YU-03112-C
Pocket tester
This tool is used to check the electrical
system.
90890-03141
YU-03141
Timing light
This tool is used to check the ignition tim-
ing.
90890-03158
Carburetor angle driver
This tool is used to turn the air screw
when adjusting the engine idling speed.
90890-04086
YM-91042
Universal clutch holder
This tool is needed to hold the clutch
boss when removing or installing the
boss nut.
90890-04097
YM-04097
Valve guide remover (ø5)
This tool is needed to remove and install
the valve guides.
90890-04098
YM-04098
Valve guide installer (ø5)
This tool is needed to install the valve
guides.
90890-04099
YM-04099
Valve guide reamer (ø5)
This tool is needed to rebore the new
valve guides.
Tool No. Tool name/Function Illustration

1 - 8
GEN
INFO
SPECIAL TOOLS
90890-04101
Valve lapper
This tool is used for lapping the valves.
90890-06754
YM-34487
Ignition checker
This tool is used to check the ignition sys-
tem components.
90890-85505
Yamaha bond No. 1215
This bond is used to seal two mating sur-
faces (e.g., crankcase mating surfaces).
Tool No. Tool name/Function Illustration

SPEC
CHAPTER 2
SPECIFICATIONS
GENERAL SPECIFICATIONS ........................................................................2-1
ENGINE SPECIFICATIONS ............................................................................2-2
CHASSIS SPECIFICATIONS ........................................................................2-10
ELECTRICAL SPECIFICATIONS .................................................................2-14
CONVERSION TABLE ..................................................................................2-16
GENERAL TIGHTENING TORQUE SPECIFICATIONS...............................2-16
TIGHTENING TORQUES ..............................................................................2-17
ENGINE TIGHTENING TORQUES.........................................................2-17
CHASSIS TIGHTENING TORQUES.......................................................2-19
LUBRICATION POINTS AND LUBRICANT TYPES ....................................2-21
ENGINE...................................................................................................2-21
CHASSIS.................................................................................................2-22
LUBRICATION DIAGRAMS..........................................................................2-23
CABLE ROUTING .........................................................................................2-25

2 - 1
SPEC
SPECIFICATIONS
GENERAL SPECIFICATIONS
Model YBR125
Model code 3D91
Dimensions
Overall length 1,980 mm (78.0 in)
Overall width 745 mm (29.3 in)
Overall height 1,080 mm (42.5 in)
Seat height 780 mm (30.7 in)
Wheelbase 1,290 mm (50.8 in)
Minimum ground clearance 175 mm (6.89 in)
Minimum turning radius 1,750 mm (68.9 in)
Weight
Wet (with oil and full fuel tank) 120.0 kg (265 lb)
Maximum load (total of cargo, rider, passen-
ger, and accessories)
200.0 kg (441 lb)
GENERAL SPECIFICATIONS

2 - 2
SPEC
ENGINE SPECIFICATIONS
ENGINE SPECIFICATIONS
Item Standard Limit
Engine
Engine type Air-cooled 4-stroke, SOHC ----
Displacement 123.7 cm3(7.55 cu.in) ----
Cylinder arrangement Forward-inclined single cylinder ----
Bore ×stroke 54.0 ×54.0 mm (2.13 ×2.13 in) ----
Compression ratio 10.0 : 1 ----
Standard compression pressure
(at sea level)
1,200 kPa (12.0 kgf/cm2, 170.7 psi) ----
Starting system Electric starter and kickstarter ----
Fuel
Recommended fuel Regular unleaded gasoline only ----
Fuel tank capacity 12.0 L (2.64 Imp gal, 3.17 US gal) ----
Fuel reserve amount 3.0 L (0.66 Imp gal, 0.79 US gal) ----
Engine oil
Type SAE10W30, SAE10W40, SAE15W40,
SAE20W40 or SAE20W50
----
Recommended engine oil grade API service SE, SF, SG type or higher ----
Lubrication system Wet sump ----
Engine oil quantity
Total amount 1.20 L (1.06 Imp qt, 1.27 US qt) ----
Periodic oil change 1.00 L (0.88 Imp qt, 1.06 US qt) ----
Oil filter type Wire mesh ----
Oil pump
Oil pump type Trochoid ----
Inner-rotor-to-outer-rotor-tip-clear-
ance
0.07 mm (0.0028 in) 0.15 mm
(0.0059 in)
Outer-rotor-to-oil-pump-housing
clearance
0.13 ~ 0.19 mm (0.0051 ~ 0.0075 in) 0.26 mm
(0.010 in)
Oil pump-housing-to-inner-rotor-and-
outer-rotor clearance
0.06 ~ 0.10 mm (0.0024 ~ 0.0039 in) 0.17 mm
(0.0067 in)
Spark plug
Model/manufacturer CR6HSA/NGK ----
Spark plug gap 0.6 ~ 0.7 mm (0.024 ~ 0.028 in) ----
Cylinder head
Volume 15.20 ~ 15.60 cm3(0.93 ~ 0.95 cu.in) ----
Maximum warpage ---- 0.05 mm
(0.0020 in)

2 - 3
SPEC
ENGINE SPECIFICATIONS
Camshaft
Drive system Chain drive (left) ----
Intake camshaft lobe dimensions
Measurement A 25.881 ~ 25.981 mm (1.0189 ~ 1.0229 in) 25.851 mm
(1.0178 in)
Measurement B 21.194 ~ 21.294 mm (0.8344 ~ 0.8383 in) 21.164 mm
(0.8332 in)
Exhaust camshaft lobe dimensions
Measurement A 25.841 ~ 25.941 mm (1.0174 ~ 1.0213 in) 25.811 mm
(1.0162 in)
Measurement B 20.997 ~ 21.097 mm (0.8267 ~ 0.8306 in) 20.967 mm
(0.8255 in)
Maximum camshaft runout ---- 0.03 mm
(0.0012 in)
Timing chain
Model/number of links 92RH2005-90M/90 ----
Tensioning system Automatic ----
Rocker arm/rocker arm shaft
Rocker arm inside diameter 10.000 ~ 10.015 mm (0.3937 ~ 0.3943 in) 10.030 mm
(0.3949 in)
Rocker arm shaft outside diameter 9.981 ~ 9.991 mm (0.3930 ~ 0.3933 in) 9.950 mm
(0.3917 in)
Rocker-arm-to-rocker-arm-shaft
clearance
0.009 ~ 0.034 mm (0.0003 ~ 0.0013 in) 0.080 mm
(0.003 in)
Item Standard Limit
A
B
A
B

2 - 4
SPEC
ENGINE SPECIFICATIONS
Valves, valve seats, valve guides
Valve clearance (cold)
Intake 0.08 ~ 0.12 mm (0.0031 ~ 0.0047 in) ----
Exhaust 0.10 ~ 0.14 mm (0.0039 ~ 0.0055 in) ----
Valve dimensions
Valve head diameter A
Intake 25.90 ~ 26.10 mm (1.0197 ~ 1.0276 in) ----
Exhaust 21.90 ~ 22.10 mm (0.8622 ~ 0.8701 in) ----
Valve face width B
Intake 1.100 ~ 3.000 mm (0.0433 ~ 0.1181 in) ----
Exhaust 1.700 ~ 2.800 mm (0.0669 ~ 0.1102 in) ----
Valve seat width C
Intake 0.90 ~ 1.10 mm (0.0354 ~ 0.0433 in) ----
Exhaust 0.90 ~ 1.10 mm (0.0354 ~ 0.0433 in) ----
Valve margin thickness D
Intake 0.40 ~ 0.80 mm (0.0157 ~ 0.0315 in) ----
Exhaust 0.80 ~ 1.20 mm (0.0315 ~ 0.0472 in) ----
Valve stem diameter
Intake 4.975 ~ 4.990 mm (0.1959 ~ 0.1965 in) 4.945 mm
(0.1945 in)
Exhaust 4.960 ~ 4.975 mm (0.1953 ~ 0.1959 in) 4.930 mm
(0.1941 in)
Valve guide inside diameter
Intake 5.000 ~ 5.012 mm (0.1969 ~ 0.1973 in) 5.050 mm
(0.1988 in)
Exhaust 5.000 ~ 5.012 mm (0.1969 ~ 0.1973 in) 5.050 mm
(0.1988 in)
Valve-stem-to-valve-guide clearance
Intake 0.010 ~ 0.037 mm (0.0004 ~ 0.0015 in) 0.080 mm
(0.0032 in)
Exhaust 0.025 ~ 0.052 mm (0.0010 ~ 0.0020 in) 0.100 mm
(0.0039 in)
Item Standard Limit
BC
D
A
Head Diameter Face Width Seat Width Margin Thickness