2012 YAMAHA YZ450F engine

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Page 179 of 228

YAMAHA YZ450F 2012  Owners Manual 6-1
FUEL TANK
FUEL SYSTEM
This section is intended for those who have basic knowledge and skill concerning the servicing of Yamaha motorcycles 
(e.g., Yamaha dealers, service engineers, etc.) Those wh

Page 181 of 228

YAMAHA YZ450F 2012  Owners Manual 6-3
FUEL TANK
2. Install:
• Fuel pump coupler
• Air scoop (left/right)
• Seat
Refer to "SEAT AND SIDE COV-
ERS" in the chapter 4.
CHECKING THE FUEL PRESSURE
1. Check:
• Pressure regulator oper

Page 184 of 228

YAMAHA YZ450F 2012  Owners Manual 6-6
THROTTLE BODY
CHECKING THE INJECTOR
Replace the fuel injector with a 
new one if you have dropped or im-
pacted it.
1. Check:
• Injectors
Damage → Replace.
CHECKING THE THROTTLE BODY
•Before

Page 185 of 228

YAMAHA YZ450F 2012  Owners Manual 7-1
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
ELECTRICAL
This section is intended for those who have basic knowledge and skill concerning the servicing of Yamaha motorcycles 
(e.g., Yamaha dealers, ser

Page 186 of 228

YAMAHA YZ450F 2012  Owners Manual 7-2
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
WIRING DIAGRAM
1. Crankshaft position sensor
2. AC magneto
3. Rectifier/regulator
4. Condenser
5. Fuel pump
6. Engine stop switch
7. ECU
8. Ignition coil
9

Page 187 of 228

YAMAHA YZ450F 2012  Owners Manual 7-3
IGNITION SYSTEM
IGNITION SYSTEM
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning engine being attributable to ignition system failure 
and for checking t

Page 188 of 228

YAMAHA YZ450F 2012  Owners Manual 7-4
IGNITION SYSTEM
SPARK GAP TEST
1. Disconnect the spark plug cap 
from spark plug.
2. Connect the dynamic spark tester 
"1" (ignition checker "2") as 
shown.
• Spark plug cap "3"
• Spark plug "

Page 191 of 228

YAMAHA YZ450F 2012  Owners Manual 7-7
THROTTLE POSITION SENSOR SYSTEM
HANDLING NOTE
Do not loosen the screw (throttle 
position sensor) "1" except when 
changing the throttle position sen-
sor due to failure because it will 
cause a d