Yamaha SR400 2014 User manual

2014
SERVICE MANUAL
SR400
SR400E
2RD-28197-E0

EAS20040
SR400
SR400E
SERVICE MANUAL
©2013 by Yamaha Motor Co., Ltd.
First edition, November 2013
All rights reserved.
Any reproduction or unauthorized use
without the written permission of
Yamaha Motor Co., Ltd.
is expressly prohibited.

EAS20071
IMPORTANT
This manual was produced by the Yamaha Motor Company, Ltd. primarily for use by Yamaha dealers
and their qualified mechanics. It is not possible to include all the knowledge of a mechanic in one man-
ual. 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 vehi-
cle unsafe and unfit for use.
Yamaha Motor Company, Ltd. is continually striving to improve all of its models. Modifications and sig-
nificant changes in specifications or procedures will be forwarded to all authorized Yamaha dealers and
will appear in future editions of this manual where applicable.
TIP
Designs and specifications are subject to change without notice.
EAS20081
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 safety 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 injury.
A NOTICE indicates special precautions that must be taken to avoid
damage to the vehicle or other property.
A TIP provides key information to make procedures easier or clearer.
WARNING
NOTICE
TIP

EAS20091
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.
•The manual is divided into chapters and each chapter is divided into sections. The current section title
“1” is shown at the top of each page.
•Sub-section titles “2” appear in smaller print than the section title.
•To help identify parts and clarify procedure steps, there are exploded diagrams “3” at the start of each
removal and disassembly section.
•Numbers “4” are given in the order of the jobs in the exploded diagram. A number indicates a disas-
sembly step.
•Symbols “5” indicate parts to be lubricated or replaced.
Refer to “SYMBOLS”.
•A job instruction chart “6” accompanies the exploded diagram, providing the order of jobs, names of
parts, notes in jobs, etc. This step explains removal and disassembly procedure only. For installation
and assembly procedure, reverse the steps.
•Jobs “7” requiring more information (such as special tools and technical data) are described sequen-
tially.
3
6
15
2
7
4

EAS20101
SYMBOLS
The following symbols are used in this manual for easier understanding.
TIP
The following symbols are not relevant to every vehicle.
SYMBOL DEFINITION SYMBOL DEFINITION
Serviceable with engine mounted Gear oil
Filling fluid Molybdenum disulfide oil
Lubricant Brake fluid
Special tool Wheel bearing grease
Tightening torque Lithium-soap-based grease
Wear limit, clearance Molybdenum disulfide grease
Engine speed Silicone grease
Electrical data YAMAHA GREASE “F”
Engine oil Apply locking agent (LOCTITE®).
Silicone fluid Replace the part with a new one.
G
M
BF
B
T
R
.
.
LS
M
S
F
E
LT
S
New

GENERAL INFORMATION 1
SPECIFICATIONS 2
PERIODIC CHECKS AND
ADJUSTMENTS 3
CHASSIS 4
ENGINE 5
FUEL SYSTEM 6
ELECTRICAL SYSTEM 7
TROUBLESHOOTING 8
EAS20110
TABLE OF CONTENTS

1
2
3
4
5
6
7
8
9
GENERAL INFORMATION
IDENTIFICATION .............................................................................................1-1
VEHICLE IDENTIFICATION NUMBER ......................................................1-1
MODEL LABEL...........................................................................................1-1
FEATURES.......................................................................................................1-2
OUTLINE OF THE FI SYSTEM..................................................................1-2
FI SYSTEM.................................................................................................1-3
FUEL LINE CHART ....................................................................................1-4
IMPORTANT INFORMATION ..........................................................................1-5
PREPARATION FOR REMOVAL AND DISASSEMBLY............................1-5
REPLACEMENT PARTS............................................................................1-5
GASKETS, OIL SEALS AND O-RINGS .....................................................1-5
LOCK WASHERS/PLATES AND COTTER PINS ......................................1-5
BEARINGS AND OIL SEALS .....................................................................1-5
CIRCLIPS ...................................................................................................1-6
RUBBER PARTS........................................................................................1-6
BASIC SERVICE INFORMATION....................................................................1-7
QUICK FASTENERS..................................................................................1-7
ELECTRICAL SYSTEM..............................................................................1-7
SPECIAL TOOLS ...........................................................................................1-12

IDENTIFICATION
1-1
EAS20130
IDENTIFICATION
EAS20140
VEHICLE IDENTIFICATION NUMBER
The vehicle identification number “1” is stamped
into the right side of the steering head pipe.
EAS20150
MODEL LABEL
The model label “1” is affixed to the frame under
the rider seat. This information will be needed to
order spare parts.
1
1

FEATURES
1-2
EAS20170
FEATURES
EAS2RD1001
OUTLINE OF THE FI SYSTEM
The main function of a fuel supply system is to provide fuel to the combustion chamber at the optimum
air-fuel ratio in accordance with the engine operating conditions and the atmospheric temperature. In
the conventional carburetor system, the air-fuel ratio of the mixture that is supplied to the combustion
chamber is created by the volume of the intake air and the fuel that is metered by the jet used in the
respective carburetor.
Despite the same volume of intake air, the fuel volume requirement varies by the engine operating con-
ditions, such as acceleration, deceleration, or operating under a heavy load. Carburetors that meter the
fuel through the use of jets have been provided with various auxiliary devices, so that an optimum air-fu-
el ratio can be achieved to accommodate the constant changes in the operating conditions of the en-
gine.
As the requirements for the engine to deliver more performance and cleaner exhaust gases increase,
it becomes necessary to control the air-fuel ratio in a more precise and finely tuned manner. To accom-
modate this need, this model has adopted an electronically controlled fuel injection (FI) system, in place
of the conventional carburetor system. This system can achieve an optimum air-fuel ratio required by
the engine at all times by using a microprocessor that regulates the fuel injection volume according to
the engine operating conditions detected by various sensors.
The adoption of the FI system has resulted in a highly precise fuel supply, improved engine response,
better fuel economy, and reduced exhaust emissions.
256789
17 16 1415 13 12 1011
134
1. Engine trouble warning light
2. Ignition coil
3. Engine temperature sensor
4. ISC (idle speed control) valve
5. Fuel injector
6. Throttle position sensor
7. ECU (engine control unit)
8. Battery
9. Lean angle sensor
10.Fuel pump
11.Catalytic converter
12.Intake air temperature sensor
13.Air induction system solenoid
14.Intake air pressure sensor
15.Crankshaft position sensor
16.Spark plug
17.O2sensor

FEATURES
1-3
EAS2RD1003
FI SYSTEM
The fuel pump delivers fuel to the fuel injector via the fuel filter. The pressure regulator maintains the
fuel pressure that is applied to the fuel injector at a certain level. Accordingly, when the energizing signal
from the ECU energizes the fuel injector, the fuel passage opens, causing the fuel to be injected into
the intake manifold only during the time the passage remain open.
Therefore, the longer the length of time the fuel injector is energized (injection duration), the greater the
volume of fuel that is supplied. Conversely, the shorter the length of time the fuel injector is energized
(injection duration), the lesser the volume of fuel that is supplied.
The injection duration and the injection timing are controlled by the ECU. Signals that are input from the
throttle position sensor, ISC (idle speed control) valve, engine temperature sensor, lean angle sensor,
crankshaft position sensor, intake air pressure sensor, intake air temperature sensor, speed sensor and
O2sensor enable the ECU to determine the injection duration. The injection timing is determined
through the signals from the crankshaft position sensor. As a result, the volume of fuel that is required
by the engine can be supplied at all times in accordance with the driving conditions.
Illustration is for reference only.
1
B
13
12
11
10
A
28
C5
4
6
7
16
9
15
14
3
1. Fuel pump
2. Fuel injector
3. ECU (engine control unit)
4. Throttle position sensor
5. Lean angle sensor
6. ISC (idle speed control) valve
7. Speed sensor
8. O2sensor
9. Catalytic converter
10.Engine temperature sensor
11.Crankshaft position sensor
12.Intake air pressure sensor
13.Throttle body
14.Intake air temperature sensor
15.Air filter case
16.Pressure regulator
A. Fuel system
B. Air system
C. Control system

FEATURES
1-4
EAS2RD1002
FUEL LINE CHART
1
A
B
25
6
34
1. Fuel tank
2. Fuel cock
3. Fuel pump case
4. Fuel pump
5. Fuel injector
6. Pressure regulator
A. Feeding side
B. Return side

IMPORTANT INFORMATION
1-5
EAS20180
IMPORTANT INFORMATION
EAS20190
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 equip-
ment.
Refer to “SPECIAL TOOLS” on page 1-12.
3. When disassembling, always keep mated
parts together. This includes gears, cylinders,
pistons and other parts that have been “mat-
ed” through normal wear. Mated parts must
always be reused or replaced as an assem-
bly.
4. During disassembly, clean all of the parts and
place them in trays in the order of disassem-
bly. This will speed up assembly and allow for
the correct installation of all parts.
5. Keep all parts away from any source of fire.
EAS20200
REPLACEMENT PARTS
Use only genuine Yamaha parts for all replace-
ments. Use oil and grease recommended by
Yamaha for all lubrication jobs. Other brands
may be similar in function and appearance, but
inferior in quality.
EAS20210
GASKETS, OIL SEALS AND O-RINGS
1. When overhauling the engine, replace all
gaskets, seals and O-rings. All gasket surfac-
es, 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.
EAS20220
LOCK WASHERS/PLATES AND COTTER
PINS
After removal, replace all lock washers/plates
“1” and cotter pins. After the bolt or nut has been
tightened to specification, bend the lock tabs
along a flat of the bolt or nut.
EAS20231
BEARINGS AND OIL SEALS
Install bearings “1” and oil seals “2” so that the
1. Oil
2. Lip
3. Spring
4. Grease

IMPORTANT INFORMATION
1-6
manufacturer 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
appropriate.
NOTICE
ECA13300
Do not spin the bearing with compressed air
because this will damage the bearing surfac-
es.
EAS20240
CIRCLIPS
Before reassembly, check all circlips carefully
and replace damaged or distorted circlips. Al-
ways replace piston pin clips after one use.
When installing a circlip “1”, make sure the
sharp-edged corner “2” is positioned opposite
the thrust “3” that the circlip receives.
EAS32080
RUBBER PARTS
Check rubber parts for deterioration during in-
spection. Some of the rubber parts are sensitive
to gasoline, flammable oil, grease, etc. Do not al-
low any items other than the specified one to
contact the parts.

BASIC SERVICE INFORMATION
1-7
EAS30380
BASIC SERVICE INFORMATION
EAS30390
QUICK FASTENERS
Rivet type
1. Remove:
•Quick fastener
TIP
To remove the quick fastener, push its pin with a
screwdriver, then pull the fastener out.
2. Install:
•Quick fastener
TIP
To install the quick fastener, push its pin so that
it protrudes from the fastener head, then insert
the fastener into the part to be secured and push
the pin “a” in with a screwdriver. Make sure that
the pin is flush with the fastener’s head.
Screw type
1. Remove:
•Quick fastener
TIP
To remove the quick fastener, loosen the screw
with a screwdriver, then pull the fastener out.
2. Install:
•Quick fastener
TIP
To install the quick fastener, insert the fastener
into the part to be secured and tighten the screw
“a”.
EAS30401
ELECTRICAL SYSTEM
Electrical parts handling
NOTICE
ECA16600
Never disconnect a battery lead while the en-
gine is running; otherwise, the electrical
components could be damaged.
NOTICE
ECA16750
When disconnecting the battery leads from

BASIC SERVICE INFORMATION
1-8
the battery, be sure to disconnect the nega-
tive battery lead first, then the positive bat-
tery lead. If a tool or similar item contacts the
vehicle while only the negative battery lead
is connected, a spark could be generated,
which is extremely dangerous.
TIP
If a battery lead is difficult to disconnect due to
rust on the battery terminal, remove the rust us-
ing hot water.
NOTICE
ECA16760
Be sure to connect the battery leads to the
correct battery terminals. Reversing the bat-
tery lead connections could damage the
electrical components.
NOTICE
ECA16770
When connecting the battery leads to the
battery, be sure to connect the positive bat-
tery lead first, then the negative battery lead.
If a tool or similar item contacts the vehicle
while only the negative battery lead is con-
nected, a spark could be generated, which is
extremely dangerous.
NOTICE
ECA16610
Turn the main switch to “OFF” before dis-
connecting or connecting an electrical com-
ponent.
NOTICE
ECA16620
Handle electrical components with special
care, and do not subject them to strong
shocks.
NOTICE
ECA16630
Electrical components are very sensitive to
and can be damaged by static electricity.
Therefore, never touch the terminals and be
sure to keep the contacts clean.

BASIC SERVICE INFORMATION
1-9
TIP
When resetting the ECU by turning the main
switch to “OFF”, be sure to wait approximately
5 seconds before turning the main switch back
to “ON”.
Checking the electrical system
TIP
Before checking the electrical system, make
sure that the battery voltage is at least 12 V.
NOTICE
ECA14371
Never insert the tester probes into the cou-
pler terminal slots. Always insert the probes
from the opposite end “a” of the coupler, tak-
ing care not to loosen or damage the leads.
NOTICE
ECA16640
For waterproof couplers, never insert the
tester probes directly into the coupler. When
performing any checks using a waterproof
coupler, use the specified test harness or a
suitable commercially available test har-
ness.
Checking the connections
Check the leads, couplers, and connectors for
stains, rust, moisture, etc.
1. Disconnect:
•Lead
•Coupler
•Connector
NOTICE
ECA16780
• When disconnecting a coupler, release the
coupler lock, hold both sections of the cou-
pler securely, and then disconnect the cou-
pler.
• There are many types of coupler locks;
therefore, be sure to check the type of cou-
pler lock before disconnecting the coupler.
a

BASIC SERVICE INFORMATION
1-10
NOTICE
ECA16790
When disconnecting a connector, do not pull
the leads. Hold both sections of the connec-
tor securely, and then disconnect the con-
nector.
2. Check:
•Lead
•Coupler
•Connector
Moisture Dry with an air blower.
Rust/stains Connect and disconnect sev-
eral times.
3. Connect:
•Lead
•Coupler
•Connector
TIP
•When connecting a coupler or connector, push
both sections of the coupler or connector to-
gether until they are connected securely.
•Make sure all connections are tight.
4. Check:
•Continuity
(with the pocket tester)
TIP
•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
Analog pocket tester
YU-03112-C

BASIC SERVICE INFORMATION
1-11
5. Check:
•Resistance
TIP
The resistance values shown were obtained at
the standard measuring temperature of 20 C
(68 F). If the measuring temperature is not 20
C (68 F), the specified measuring conditions
will be shown.
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
Intake air temperature sensor re-
sistance
5.40–6.60 kat 0 C (32 F)
290–390 at 80 C (176 F)