2015 YAMAHA YZ450F engine

EAS1SL5005
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 OPERATED BY AN EXPERIENCED RIDER ONLY.
Do not attempt to operate this machine at maximum power until you are totally familiar with its char-
acteristics.
• 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, always 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 MACHINE IN PROPER WORKING ORDER.
For safety and reliability, the machine must be properly maintained. Always perform the pre-oper-
ation checks indicated in this manual.
Correcting a mechanical problem before you ride may prevent an accident.
• GASOLINE IS HIGHLY FLAMMABLE.
Always turn off the engine while refueling. Take care to not spill any gasoline on the engine or ex-
haust system. Never refuel in the vicinity of an open flame, or while smoking.
• GASOLINE CAN CAUSE INJURY.
If you should swallow some gasoline, inhale excess gasoline vapors, or allow any gasoline to get
into your eyes, contact a doctor immediately. If any gasoline spills onto your skin or clothing, imme-
diately wash skin areas with soap and water, 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
poisonous. These fumes contain carbon monoxide, which by itself is odorless and colorless. Car-
bon monoxide is a dangerous gas which can cause unconsciousness or can be lethal.
• PARK THE MACHINE CAREFULLY; 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 AND MUFFLER WILL BE VERY HOT AFTER THE ENGINE 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 MACHINE BEFORE TRANSPORTING IT.
For safety, drain the gasoline from the fuel tank before transporting the vehicle.

EAS1SL5007
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 Locking agent (LOCTITE®)
Engine oil Replace the part with a new one.
G
M
BF
B
T R..
LS
M
S
LT
E
New

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TABLE OF CONTENTS
GENERAL INFORMATION
SPECIFICATIONS
PERIODIC CHECKS AND ADJUST-
MENTS
CHASSIS
ENGINE
COOLING SYSTEM
FUEL SYSTEM
ELECTRICAL SYSTEM
TROUBLE SHOOTING
TUNING

1
GENERAL INFORMATION
LOCATION OF IMPORTANT LABELS............................................................ 1-1
DESCRIPTION.................................................................................................. 1-4
IDENTIFICATION............................................................................................. 1-5
VEHICLE IDENTIFICATION NUMBER ...................................................... 1-5
ENGINE SERIAL NUMBER ....................................................................... 1-5
MODEL LABEL........................................................................................... 1-5
FEATURES....................................................................................................... 1-6
OUTLINE OF THE FI SYSTEM .................................................................. 1-6
FI SYSTEM................................................................................................. 1-7
INCLUDED PARTS.......................................................................................... 1-8
SIDESTAND ............................................................................................... 1-8
SPARK PLUG WRENCH ........................................................................... 1-8
NIPPLE WRENCH...................................................................................... 1-8
HANDLEBAR PROTECTOR ...................................................................... 1-8
FUEL HOSE JOINT COVER ...................................................................... 1-8
COUPLER FOR CONNECTING OPTIONAL PART................................... 1-8
IMPORTANT INFORMATION........................................................................ 1-10
PREPARATION FOR REMOVAL AND DISASSEMBLY.......................... 1-10
REPLACEMENT PARTS.......................................................................... 1-10
GASKETS, OIL SEALS AND O-RINGS ................................................... 1-11
LOCK WASHERS/PLATES AND COTTER PINS .................................... 1-11
BEARINGS AND OIL SEALS ................................................................... 1-11
CIRCLIPS ................................................................................................. 1-11
BASIC SERVICE INFORMATION.................................................................. 1-12
ELECTRICAL SYSTEM............................................................................ 1-12
SPECIAL TOOLS........................................................................................... 1-15
CONTROL FUNCTIONS................................................................................ 1-20
ENGINE STOP SWITCH .......................................................................... 1-20
CLUTCH LEVER...................................................................................... 1-20
SHIFT PEDAL .......................................................................................... 1-20
KICKSTARTER LEVER............................................................................ 1-20
THROTTLE GRIP ..................................................................................... 1-20
FRONT BRAKE LEVER ........................................................................... 1-20
REAR BRAKE PEDAL.............................................................................. 1-21
STARTER KNOB/IDLE SCREW .............................................................. 1-21
FUEL TANK CAP ..................................................................................... 1-21

STARTING AND BREAK-IN.......................................................................... 1-22
FUEL ........................................................................................................ 1-22
STARTING A COLD ENGINE .................................................................. 1-22
STARTING A WARM ENGINE ................................................................. 1-23
BREAK-IN PROCEDURES ...................................................................... 1-23
MAINTENANCE AFTER BREAK-IN.............................................................. 1-24
MAJOR MAINTENANCE .......................................................................... 1-24
TORQUE-CHECK POINTS............................................................................ 1-25
CLEANING AND STORAGE.......................................................................... 1-27
CLEANING ............................................................................................... 1-27
STORAGE ................................................................................................ 1-27

DESCRIPTION
1-4
EAS1SL5009
DESCRIPTION
TIP
Designs and specifications of the vehicle are subject to change without notice. Therefore, please
note that the descriptions in this manual may be different from those for the vehicle you have pur-
chased.1. Clutch lever 10. Coolant drain bolt
2. Front brake lever 11. Rear brake pedal
3. Throttle grip 12. Air filter
4. Radiator cap 13. Drive chain
5. Fuel tank cap 14. Shift pedal
6. Engine stop switch 15. Oil level check window
7. Fuel tank 16. Starter knob/idle screw
8. Kickstarter lever 17. Front fork
9. Radiator
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IDENTIFICATION
1-5
EAS1SL5010
IDENTIFICATION
There are two significant reasons for knowing
the serial number of your vehicle:
1. When ordering parts, you can give the num-
ber to your Yamaha dealer for positive iden-
tification of the model you own.
2. If your vehicle is stolen, the authorities will
need the number to search for and identify
your vehicle.
EAS1SL5011VEHICLE IDENTIFICATION NUMBER
The vehicle identification number “1” is
stamped into the right side of the frame.
EAS1SL5012ENGINE SERIAL NUMBER
The engine serial number “1” is stamped into
the elevated part of the right-side of the engine.
EAS1SL5013MODEL LABEL
The model label “1” is affixed to the rear frame.
This information will be needed to order spare
parts.
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FEATURES
1-6
EAS20170
FEATURES
EAS1SL5014OUTLINE 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 to be supplied to the
combustion chamber is determined by the amount of intake air and fuel that is measured on the basis
of the jets to be used in the carburetor.
Despite the same amount of intake air, the fuel amount requirement varies with the engine operating
conditions (acceleration, deceleration, and operation under a heavy load). The carburetor that mea-
sures fuel through the use of jets are provided with various auxiliary devices, so that the optimum air
fuel ratio can be obtained to accommodate frequent changes in the operating conditions of the en-
gine. This model has adopted an electronically controlled fuel injection (FI) system, in place of the
conventional carburetor system. This system can obtain the optimum air-fuel ratio required by the
engine at all times by using a microprocessor that regulates the fuel injection amount according to
the engine operating conditions detected by various sensors.
1. Fuel injector
2. Throttle position sensor
3. Intake air pressure sensor
4. Intake air temperature sensor
5. ECU
6. Fuel pump
7. Condenser
8. Crankshaft position sensor
9. Coolant temperature sensor
10.Ignition coil
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