2016 YAMAHA YZ450F fuel pressure

PRE-OPERATION INSPECTION AND MAINTENANCE
3-7
EASB111066
PRE-OPERATION INSPECTION AND MAINTENANCE
Before riding for break-in operation, practice or a race, make sure the machine is in good operating
condition.
Before using this machine, check the following points.
EASB111067GENERAL INSPECTION AND MAINTENANCE
TIP
Perform usual maintenance enough so that, in the race course, a confirmation of that and simple set-
ting adjustments may only be left, in order to get enough time to use effectively.ITEM inspect Page
CoolantCheck that coolant is filled up to the radiator cap.
Check the cooling system for leakage.3-8 – 10
FuelCheck that a fresh gasoline is filled in the fuel tank.
Check the fuel line for leakage.1-21
Engine oilCheck that the oil level is correct. Check the crank-
case and oil line for leakage.3-14 – 16
Gear shifter and clutchCheck that gears can be shifted correctly in order and
that the clutch operates smoothly.3-10 – 11
Throttle grip/HousingCheck that the throttle grip operation and free play
are correctly adjusted. Lubricate the throttle grip and
housing, if necessary.3-11 – 12
BrakesCheck the play of front brake and effect of front and
rear brake.3-22 – 28
Drive chainCheck drive chain slack and alignment. Check that
the drive chain is lubricated properly.3-28 – 29
4-66 – 67
WheelsCheck for excessive wear and tire pressure. Check
for loose spokes and have no excessive play.3-34
SteeringCheck that the handlebar can be turned smoothly and
have no excessive play.3-35 – 36
Front forks and rear
shock absorberCheck that they operate smoothly and there is no oil
leakage.3-29 – 33
Cables (wires)Check that the clutch and throttle cables move
smoothly. Check that they are not caught when the
handlebars are turned or when the front forks travel
up and down.—
Exhaust pipeCheck that the exhaust pipe is tightly mounted and
has no cracks.3-14
Rear wheel sprocketCheck that the rear wheel sprocket tightening bolt is
not loose.4-8 – 9
Lubrication Check for smooth operation. Lubricate if necessary. 3-12, 3-36
Bolts and nutsCheck the chassis and engine for loose bolts and
nuts.1-24 – 25
Lead connectorsCheck that the AC magneto, ECU and ignition coil are
connected tightly.1-10 – 12
SettingsIs the machine set suitably for the condition of the rac-
ing course and weather or by taking into account the
results of test runs before racing? Are inspection and
maintenance completely done?10-1 – 8

ENGINE
3-16
d. Install the oil strainer.
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6. Install:
• Engine oil drain bolt
• Drain bolt
7. Pour the specified amount of engine oil into
the oil filler cap hole.
8. Install:
• Oil filler cap
9. Check:
• Oil level
Refer to “CHECKING THE ENGINE OIL
LEVEL” on page 3-14.
10.Check:
• Engine oil pressure
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a. Slightly loosen the oil pressure check bolt
“1”.
EWA
WARNING
When the engine is started with the check
bolt removed, oil will spout; therefore, al-
ways loosen it before the checkup.
Start the engine and keep it idling until oil
starts to seep from the oil pressure check
bolt.
EWA
WARNING
Always keep the engine idling speed during
the checkup without increasing the engine
speed.
ECA
NOTICE
If no engine oil seeps out after one minute,
immediately turn the engine off so it will not
seize.
b. If no engine oil seeps out, check the engine
oil for leaks, and the engine oil passage and
the oil pump for damage.
c. Check the oil pressure again.
d. Tighten the oil pressure check bolt.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲EASB111086ADJUSTING THE ENGINE IDLING SPEED
TIP
• Because the air pressure is lower at high alti-
tudes, the air-fuel mixture will become richer.
If the idling speed is low, turn the starter knob/
idle screw a few clicks counterclockwise to in-
crease the speed before the adjustment.
• Before adjusting the engine idling speed,
make sure that the air filter element is not
clogged, the engine compression is proper,
and the throttle grip free play is proper.
• Adjust the engine idling speed with the starter
knob/idle screw pushed in completely. Oil strainer bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
Drain bolt
20 Nm (2.0 m·kgf, 14 ft·lbf)
Engine oil quantity
With oil filter element replace-
ment
0.69 L (0.73 US qt, 0.61 Imp.qt)
Quantity (disassembled)
0.95 L (1.00 US qt, 0.84 Imp.qt)
1
2New
T R..
New
T R..
Oil pressure check bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
1
T R..

7
FUEL SYSTEM
FUEL TANK...................................................................................................... 7-1
REMOVING THE FUEL TANK ................................................................... 7-2
REMOVING THE FUEL PUMP .................................................................. 7-2
CHECKING THE FUEL PUMP BODY........................................................ 7-2
INSTALLING THE FUEL PUMP ................................................................. 7-2
INSTALLING THE FUEL TANK.................................................................. 7-3
CHECKING THE FUEL PRESSURE ......................................................... 7-3
CHECKING THE DAMPER ........................................................................ 7-4
CHECKING AND REPLACING THE PROTECTOR .................................. 7-4
THROTTLE BODY............................................................................................ 7-5
CHECKING THE INJECTOR ..................................................................... 7-8
CHECKING THE THROTTLE BODY ......................................................... 7-8
CHECKING THE THROTTLE BODY JOINT .............................................. 7-8
ADJUSTING THE THROTTLE POSITION SENSOR................................. 7-9

FUEL TANK
7-2
EASB111305REMOVING THE FUEL TANK
1. Extract the fuel in the fuel tank through the
fuel tank cap with a pump.
2. Remove:
• Fuel hose coupler
EWA
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.
ECA
NOTICE
Make sure that the fuel hose is disconnect-
ed by hand. Do not forcefully disconnect the
hose with tools.
TIP
• To disconnect the fuel hose from the fuel tank,
remove the fuel hose connector holder “a”,
and then slide the fuel hose connector cover.
• To remove the fuel hose from the fuel rail,
slide the fuel hose connector cover “1” on the
end of the hose in the direction of the arrow
shown, press the two buttons “2” on the sides
of the connector, and then remove the hose.
• Before removing the hose, place a few cloths
in the area under where it will be removed.
• To prevent sand, dust, and other foreign ma-
terials from entering the fuel pump, install the
included fuel hose joint cover 1 “3” and the
fuel hose joint cover 2 “4” onto the disconnect-
ed fuel hose and the fuel pump.3. Remove:
• Side cover (left/right)
• Seat
• Air scoop (left/right)
• Fuel tank
TIP
Do not set the fuel tank down on the installation
surface of the fuel pump. Be sure to lean the
fuel tank against a wall or the like.
EASB111306REMOVING THE FUEL PUMP
1. Remove:
• Fuel pump
ECA
NOTICE
Do not drop the fuel pump or give it a strong
shock.
EASB111307CHECKING THE FUEL PUMP BODY
1. Check:
• Fuel pump body
Obstructions  Clean.
Cracks/damage  Replace the fuel pump
assembly.
EASB111308INSTALLING THE FUEL PUMP
1. Install:
• Fuel pump gasket
• Fuel pump
• Fuel pump bracket
a
1
2
Fuel pump bolts
4.0 Nm (0.40 m·kgf, 2.9 ft·lbf)
3 4
New
T R..

FUEL TANK
7-3
TIP
• Take care not to damage the installation sur-
faces of the fuel tank.
• Always use a new fuel pump gasket.
• Install the lip on the fuel pump gasket upward.
• Install the fuel pump as shown in the figure.
• Align the projection “a” on the fuel pump with
the slot “b” in the fuel pump bracket.
• Tighten the fuel pump bolts in the proper tight-
ening sequence as shown.
EASB111309INSTALLING THE FUEL TANK
1. Install:
• Fuel tank
2. Connect:
• Fuel hose
ECA
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.
EASB111310CHECKING THE FUEL PRESSURE
1. Check:
• Fuel pressure
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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.
EWA
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.
ECA
a
b
4 1
2
6
53
1
a

FUEL TANK
7-4
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.
e. Start the engine.
f. Measure the fuel pressure.
Out of specification  Replace the fuel
pump.
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EASB111311CHECKING 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.
EASB111312CHECKING AND REPLACING THE PRO-
TECTOR
1. Check:
• Protector “1”
Wear/damage  Replace.
TIP
Affix the protector as shown. Pressure gauge
90890-03153
YU-03153
Fuel pressure adapter
90890-03186
YM-03186
Fuel line pressure at idling
324.0 kPa (3.24 kgf/cm
2, 47.0
psi)
1
2
A. Left
B. Right
(3.31 in) (4.53 in)
84 mm 115 mm3 1
13a
2
(3.31 in) (4.53 in)84 mm 115 mm
1
1
A
0 mm
(0 in)
B
1
1
15 mm
(0.59 in)

THROTTLE BODY
7-5
EASB111313
THROTTLE BODY
Removing the throttle body
Order Part name Q’ty Remarks
Seat Refer 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 tank Refer to “FUEL TANK” on page 7-1.
ECU Refer to “ENGINE REMOVAL” on page 5-1.
Ignition coil Refer to “ENGINE REMOVAL” on page 5-1.
1 Intake air temperature sensor coupler 1 Disconnect.
2 Air filter case 1
3 Fuel injector coupler 1 Disconnect.
4 Intake air pressure sensor coupler 1 Disconnect.
5 Throttle position sensor coupler 1 Disconnect.
6 Throttle cable cover 1
7 Throttle cable 2
8 Fuel hose 1
2
1
6
10
11
9
8
3
7
5
4
10 Nm (1.0 m kgf, 7.2 ft lbf)
7 Nm (0.7 m kgf, 5.1 ft lbf)
3.5 Nm (0.35 m kgf, 2.5 ft lbf)
3.0 Nm (0.30 m kgf, 2.2 ft lbf)
3.5 Nm (0.35 m kgf, 2.5 ft lbf)

THROTTLE BODY
7-7
Removing the injector
Order Part name Q’ty Remarks
1 Fuel inlet pipe 1
2Injector 1
3 Gaskets 1
4 Throttle position sensor 1
5 Intake air pressure sensor 1
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