fuel YAMAHA YZ450F 2014 Service Manual

FUEL TANK
7-3
EAS1SL1310INSTALLING THE FUEL TANK
1. Install:
• Fuel tank
2. Connect:
• Fuel hoseECA33DD069
NOTICE
• Connect the fuel hose securely, and check
that the orientation of the installed fuel
hose holder is correct.
• Take care not to kink or pinch the fuel
hose.
TIP
• Insert the fuel hose into the fuel pipe securely
until you hear a “click.”
• Slide the fuel hose connector cover “1” at the
hose end in the direction of the arrow.
• Install the fuel hose connector holder “a.”
• Check that the fuel hose and the fuel pump
lead are routed through the guide on the cov
-
er.
3. Connect:
• Fuel pump coupler
4. Install:
• Air scoop (left/right)
• Seat
• Side cover (left/right)
Refer to “GENERAL CHASSIS” on page 4-
1.
EAS1SL1311CHECKING THE FUEL PRESSURE
1. Check:
• Fuel pressure
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Remove the side cover (left/right), the seat
and the air scoop (left/right).
Refer to “GENERAL CHASSIS” on page 4-
1.
b. Remove the fuel tank bolt and lift the fuel
tank.
c. Disconnect the fuel hose from the fuel
pump.
Refer to “REMOVING THE FUEL TANK” on
page 7-2.EWA1DX1008
WARNING
Cover the fuel hose connection with a cloth
when disconnecting it. This is because re
-
sidual pressure in the fuel hose could cause
fuel to spurt out when the hose is removed.
ECA1DX1025
NOTICE
Make sure that the fuel hose is disconnect-
ed by hand. Do not forcibly disconnect the
hose with tools.
d. Connect the pressure gauge “1” and the fuel
pressure adapter “2” to the fuel hose.
a
b
4 1
2
6
53
1Pressure gauge
90890-03153
YU-03153
Fuel pressure adapter
90890-03186
YM-03186
a

FUEL TANK
7-4
e. Start the engine.
f. Measure the fuel pressure.
Out of specification  Replace the fuel
pump.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS1SL1312CHECKING THE DAMPER
1. Check:
• Damper 1 “1”
• Damper 2 “2”
• Damper 3 “3”
Wear/damage  Replace.
TIP
• Affix dampers 1 and 3 with the arrow on each
damper pointing outward.
• Affix the damper 2 with its projection “a” facing
the rear of the vehicle.
EAS1SL1313
CHECKING AND REPLACING THE PRO-
TECTOR
1. Check:
• Protector “1”
Wear/damage  Replace.
TIP
Affix the protector as shown.
Fuel pressure
324.0 kPa (3.24 kgf/cm2, 47.0
psi)
1
2
84 mm
(3.31 in)115 mm
(4.53 in)
84 mm
(3.31 in)115 mm
(4.53 in)
3 1
13a
2
A. Left
B. Right
1
1
0 mm
(0 in)
A
B
1
15 mm
(0.59 in)
1

THROTTLE BODY
7-5
EAS1SL1314
THROTTLE BODY
Removing the throttle body
OrderPart nameQ’tyRemarks
SeatRefer to “GENERAL CHASSIS” on page 4-1.
Side cover (left/right)Refer to “GENERAL CHASSIS” on page 4-1.
Air scoop (left/right)Refer to “GENERAL CHASSIS” on page 4-1.
Fuel tankRefer to “FUEL TANK” on page 7-1.
ECURefer to “ENGINE REMOVAL” on page 5-1.
Ignition coilRefer to “ENGINE REMOVAL” on page 5-1.
1Intake air temperature sensor coupler1Disconnect.
2Air filter case1
3Fuel injector coupler1Disconnect.
4Intake air pressure sensor coupler1Disconnect.
5Throttle position sensor coupler1Disconnect.
6Throttle cable cover1
7Throttle cable2
8Fuel hose1
9Exhaust pipe bracket1
2
1
6
10
11
9
8
3
7
5
4
3.5 Nm (0.35 mkgf, 2.5 ftIbf)T.R.
3.5 Nm (0.35 mkgf, 2.5 ftIbf)T.R.
7 Nm (0.7 mkgf, 5.1 ftIbf)T.R.
3.0 Nm (0.30 mkgf, 2.2 ftIbf)T.R.
10 Nm (1.0 mkgf, 7.2 ftIbf)T.R.

THROTTLE BODY
7-7
Removing the injector
OrderPart nameQ’tyRemarks
1Fuel inlet pipe1
2Injector1
3Gaskets1
4Throttle position sensor1
5Intake air pressure sensor1
For installation, reverse the removal proce-dure.
1
2 (2)
(2)5
43
T.R.3.4 Nm (0.34 mlbf) kgf, 2.5 ft
T.R.5 Nm (0.5 mlbf) kgf, 3.6 ft
T.R.3.4 Nm (0.34 mlbf) kgf, 2.5 ft

THROTTLE BODY
7-8
EAS1SL1315CHECKING THE INJECTOR
1. Check:
• Injector
Obstruction  Replace, and check the fuel
pump and the fuel injection system.
Refer to “FUEL INJECTION SYSTEM” on
page 8-10.
Deposits  Replace.
Damage  Replace.
2. Check:
• Injector resistance
Refer to “CHECKING THE FUEL INJEC-
TOR” on page 8-47.
EAS1SL1316CHECKING THE THROTTLE BODY
1. Check:
• Throttle body
Cracks/damage  Replace.
2. Check:
• Fuel passages
Obstructions  Clean.ECA1DX1027
NOTICE
• Before removing the throttle body, clean
the area around the throttle body to pre
-
vent dirt and other foreign material from
falling into the engine.
• If the throttle body is subject to strong
shocks or dropped during cleaning, re
-
place it.
• Do not use any caustic carburetor clean-
ing solution.
• Do not directly push the throttle valves to
open them.
• Do not loosen the throttle valve stopper
screw “1”, throttle valve pulley nut “2”, or
throttle valve screw “3”. A loss of perfor
-
mance may occur.
• Do not use compressed air to clean the
throttle body. Foreign materials may ad
-
here to the intake air pressure sensor pas-
sage “a” and fuel injector “b” in the
throttle body.
3. Check:
• Starter knob/idle screw passage “c”
Obstruction  Blow out with compressed
air.
EAS1SL1317CHECKING THE THROTTLE BODY JOINT
1. Check:
• Throttle body joint “1”
Crack/damage  Replace.
EAS1SL1318
1 2
3
ba
c
1

8
ELECTRICAL SYSTEM
IGNITION SYSTEM.......................................................................................... 8-2
CIRCUIT DIAGRAM ................................................................................... 8-2
TROUBLESHOOTING ............................................................................... 8-4
CHARGING SYSTEM....................................................................................... 8-6
CIRCUIT DIAGRAM ................................................................................... 8-6
TROUBLE SHOOTING .............................................................................. 8-8
FUEL INJECTION SYSTEM........................................................................... 8-10
CIRCUIT DIAGRAM ................................................................................. 8-10
YAMAHA DIAGNOSTIC TOOL ................................................................ 8-12
TROUBLESHOOTING DETAILS ............................................................. 8-13
FUEL PUMP SYSTEM.................................................................................... 8-32
CIRCUIT DIAGRAM ................................................................................. 8-32
TROUBLESHOOTING ............................................................................. 8-34
ELECTRICAL COMPONENTS....................................................................... 8-36
CHECKING THE SWITCHES .................................................................. 8-38
CHECKING THE IGNITION SPARK GAP................................................ 8-41
CHECKING THE SPARK PLUG CAP ...................................................... 8-41
CHECKING THE IGNITION COIL ............................................................ 8-41
CHECKING THE CRANKSHAFT POSITION SENSOR........................... 8-42
CHECKING THE ECU .............................................................................. 8-43
CHECKING THE STATOR COIL ............................................................. 8-43
CHECKING THE RECTIFIER/REGULATOR ........................................... 8-43
CHECKING THE COOLANT TEMPERATURE SENSOR........................ 8-44
CHECKING THE THROTTLE POSITION SENSOR ................................ 8-44
CHECKING THE THROTTLE POSITION SENSOR 
INPUT VOLTAGE .................................................................................... 8-43
CHECKING THE INTAKE AIR PRESSURE SENSOR ............................ 8-46
CHECKING THE INTAKE AIR TEMPERATURE SENSOR ..................... 8-46
CHECKING THE NEUTRAL SWITCH ..................................................... 8-46
CHECKING THE FUEL INJECTOR ......................................................... 8-47

IGNITION SYSTEM
8-4
TROUBLESHOOTING
The ignition system fails to operate (no spark or intermittent spark).
TIP
Before troubleshooting, remove the following part(s):
1. Side cover (left/right)
2. Seat
3. Fuel tank
4. Air scoop (left/right)
5. Air filter case cover
1. Check the ignition system wire har-
ness connections.
NG Reconnect.
OK 
2. Check the spark plug.
Refer to “CHECKING THE SPARK
PLUG” on page 3-35.
NG 
Correct or replace the spark plug.
OK 
3. Check the ignition spark gap.
Refer to “CHECKING THE IGNI-
TION SPARK GAP” on page 8-41.
OK 
The ignition system circuit is OK.
NG 
4. Check the ignition coil.
Refer to “CHECKING THE IGNI-
TION COIL” on page 8-41.
NG 
Replace the ignition coil.
OK 
5. Check the engine stop switch.
Refer to “CHECKING THE
SWITCHES” on page 8-38.
NG 
Replace the engine stop switch.
OK 
6. Check the crankshaft position sen-
sor.
Refer to “CHECKING THE CRANK-
SHAFT POSITION SENSOR” on
page 8-42.
NG 
Replace the crankshaft position sensor.
OK 
7. Check the stator coil.
Refer to “CHECKING THE STA-
TOR COIL” on page 8-43.
NG 
Replace the stator coil.
OK 

FUEL INJECTION SYSTEM
8-10
EAS1SL1325
FUEL INJECTION SYSTEM
EAS1SL1326CIRCUIT DIAGRAM
B/LGy
BR
A
A
AA
B
RR R R R R R
B
B
B
RR
R
Lg
LgB/WB/Y
B/YB
B
BP
PP
Sb
B/LP/B
P/B
YL
YL
L
G/WBr/W
G/WBr/W
B/LB/L
B/L
B/L
B/R
B/R
R/B
R/B
O
OROR
OR
R
R
SbB
GyR
B/W
P L B/L
B/L Gy B/L B/L B/L B/L B/L
LL
PP
BBBB
PP
Sb
RB
B/RR
RB
B/Y PSb
BB
RR/B
LYB/L
B/W RLg
B/LBr/W
B/L P/B LB/LG/W
BB/Y
BB/L B/L B/L B/L B/L B/LBBBBRR
PPPL L LRR RR R
B
O P
Gy
R
B/Y Sb
P/B
R/B Lg B/RG/WBr/WB/L L Y
RB
B/L
Gy
R
O
O
R(BLACK) (BLACK)
B/W
4
1
3
2
5
67
8
10
9
1211
13
1415
16
17

FUEL INJECTION SYSTEM
8-11
EAS1SL1327
1. Crankshaft position sensor
2. AC magneto
3. Rectifier/regulator
4. Joint connector
5. Condenser
7. Engine stop switch
8. Neutral switch
9. ECU
12.Fuel injector
14.Intake air temperature sensor
15.Coolant temperature sensor
16.Throttle position sensor
17.Intake air pressure sensor

FUEL INJECTION SYSTEM
8-12
YAMAHA DIAGNOSTIC TOOL
This model uses the Yamaha diagnostic tool to identify malfunctions.
For information about using the Yamaha diagnostic tool, refer to the operation manual that is included
with the tool.
FEATURES OF THE YAMAHA DIAGNOSTIC TOOL
A diagnosis can be made more quickly than traditional methods with the Yamaha diagnostic tool.
Using this software, ECU and sensor data, as well as fault diagnosis, vehicle maintenance, and any
necessary information can be recorded and displayed on your computer screen through a USB
adapter connected to the computer interface with a communication cable connected to the vehicle's
ECU.
Data obtained in various functions can be saved as vehicle history, and can be accumulated.
FUNCTIONS OF THE YAMAHA DIAGNOSTIC TOOL
However, the diagnostic tool cannot be used to freely change the basic vehicle functions, such as
adjusting the ignition timing.
CONNECTING THE YAMAHA DIAGNOSTIC TOOL
1. Remove the coupler for connecting setting tool.
Yamaha diagnostic tool
90890-03215
Fault diagnosis modeFault codes recorded on the ECU are read, and the con-
tents are displayed.
Function diagnostic modeCheck the operation of the output value of each sensor
and actuator.
Inspection modeDetermine whether each sensor or actuator is functioning
properly.
CO adjustment modeAdjust the concentration of CO admissions during idling.
Monitoring modeDisplays a graph of sensor output values for actual oper-
ating conditions.
Logging modeRecords and saves the sensor output value in actual driv-
ing conditions.
View logDisplays the logging data.
ECU rewriteIf necessary, the ECU is rewritten using the ECU rewrite
data provided by Yamaha. Ignition timing adjustment, etc.
cannot be changed from the vehicle's original state.