Yamaha V STAR 950 User manual

Fix it like a Pro
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©2007 Repairpro Manuals

EAS20090
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 dis-
assembly 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.
• Jobs “7” requiring more information (such as special tools and technical data) are described
sequentially.

EAS20100
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 Apply locking agent (LOC-
TITE®).
Engine oil Replace the part with a new
one.

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

1
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
INSTRUMENT FUNCTIONS ..................................................................1-4
IMPORTANT INFORMATION .......................................................................1-6
PREPARATION FOR REMOVAL AND DISASSEMBLY..........................1-6
REPLACEMENT PARTS.........................................................................1-6
GASKETS, OIL SEALS AND O-RINGS..................................................1-6
LOCK WASHERS/PLATES AND COTTER PINS ...................................1-6
BEARINGS AND OIL SEALS .................................................................1-7
CIRCLIPS ...............................................................................................1-7
CHECKING THE CONNECTIONS ...............................................................1-8
SPECIAL TOOLS..........................................................................................1-9

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. This
information will be needed to order spare
parts.
2
3
1
1

FEATURES
1-2
EAS20170
FEATURES
EAS5S71022
OUTLINE OF THE FI SYSTEM
The main function of a fuel supply system is to provide fuel to the combustion chamber at the opti-
mum air-fuel ratio in accordance with the engine operating conditions and the atmospheric tempera-
ture. 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
conditions, 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-fuel ratio can be achieved to accommodate the constant changes in the operating con-
ditions of the engine.
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 man-
ner. To accommodate 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.
1. Air temperature sensor
2. Intake air pressure sensor
3. Engine trouble warning light
4. Fuel pump
5. Front cylinder injector
6. Rear cylinder injector
7. Throttle position sensor
8. Spark plug
9. Speed sensor
10.Relay unit (fuel pump relay)
11.ECU (engine control unit)
12.O2sensor
13.Lean angle sensor
14.ISC (idle speed control) unit
15.Crankshaft position sensor
16.Rear cylinder ignition coil
17.Front cylinder ignition coil
18.Engine temperature sensor

FEATURES
1-3
EAS5S71020
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 only 392 kPa (3.92 kg/cm², 56.9 psi). Accordingly,
when the energizing signal from the ECU energizes the fuel injector, the fuel passage opens, caus-
ing the fuel to be injected into the intake manifold only during the time the passage remains 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 ener-
gized (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, crankshaft position sensor, intake air pressure sensor, air temperature
sensor, engine temperature sensor, lean angle 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.
15
A
1
2
3
C
12
13
14
B
9
11
4
8
7
65
Front
Rear
10
16
1. Fuel pump
2. Fuel injector
3. Ignition coil
4. ECU (engine control unit)
5. Air temperature sensor
6. Lean angle sensor
7. ISC (idle speed control) unit
8. Throttle position sensor
9. O2sensor
10.Engine temperature sensor
11.Catalytic converter
12.Crankshaft position sensor
13.Intake air pressure sensor
14.Throttle body
15.Air filter case
16.Speed sensor
A. Fuel system
B. Air system
C. Control system