2016 YAMAHA YZ250F fuel pressure

ENGINE
3-16
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.
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EAS1SM9085ADJUSTING 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.
1. Start the engine, and warm this up until the
oil has reached the specified temperature.
2. Attach the pocket tester with temperature
probe “1” to the oil drain bolt. Engine oil quantity
Without oil filter element replace-
ment
0.71 L (0.75 US qt, 0.62 Imp.qt)
With oil filter element replace-
ment
0.73 L (0.77 US qt, 0.64 Imp.qt)
Quantity (disassembled)
0.90 L (0.95 US qt, 0.79 Imp.qt)
1
Oil pressure check bolt
10 Nm (1.0 m·kgf, 7.2 ft·lbf)
Oil temperature
55–65 °C (131–149 °F)
T R..
1

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
EAS1SM9305REMOVING 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.
EAS1SM9306REMOVING THE FUEL PUMP
1. Remove:
• Fuel pump
ECANOTICE
Do not drop the fuel pump or give it a strong
shock.
EAS1SM9307CHECKING THE FUEL PUMP BODY
1. Check:
• Fuel pump body
Obstructions  Clean.
Cracks/damage  Replace the fuel pump
assembly.
EAS1SM9308INSTALLING THE FUEL PUMP
1. Install:
• Fuel pump gasket
• Fuel pump
• Fuel pump bracket
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.
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
EAS1SM9309INSTALLING 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.
EAS1SM9310CHECKING 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
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
1
Pressure 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.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲EAS1SM9311CHECKING 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.
EAS1SM9312CHECKING AND REPLACING THE PRO-
TECTOR
1. Check:
• Protector “1”
Wear/damage  Replace.
TIP
Affix the protector as shown.
Fuel line pressure at idling
324.0 kPa (3.24 kgf/cm
2, 47.0
psi)
1
2
(3.31 in) (4.53 in)
84 mm 115 mm3 1
13a
2
(3.31 in) (4.53 in)84 mm 115 mm
A. Left
B. Right
1
1
A
0 mm
(0 in)
B
1
1
15 mm
(0.59 in)

THROTTLE BODY
7-5
EAS1SM9313
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
9 Exhaust pipe bracket 1
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
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

THROTTLE BODY
7-8
EAS1SM9314CHECKING THE INJECTOR
1. Check:
• Injectors
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.
EAS1SM9315CHECKING THE THROTTLE BODY
1. Check:
• Throttle body
Cracks/damage  Replace.
2. Check:
• Fuel passages
Obstructions  Clean.
ECA
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.
EAS1SM9316CHECKING THE THROTTLE BODY JOINT
1. Check:
• Throttle body joint “1”
Crack/damage  Replace.
1 2
3
ba
c
1