2011 YAMAHA YZ450F fuel cap

3-10
ENGINE
CHANGING THE ENGINE OIL
1. Start the engine and let it warm up for several minutes.
2. Stop the engine and place an oil pan under the drain bolt.
3. Remove: • Oil filler cap "1"
• Drain bolt (with gasket) "2"
• Drain bolt (with gasket) "3"Drain the engine oil.
4. If the oil filter is to be replaced dur- ing this oil change, remove the fol-
lowing parts and reinstall them.
Replacement steps:
a. Remove the oil filter element cov-er "1" and oil filter element "2".
b. Check the O-rings "3", if cracked or damaged, replace them with a
new one.
c. Install the oil filter element and oil filter element cover.
5. Install:• Gaskets
• Oil drain bolt (oil pan)
• Oil drain bolt (oil tank)
6. Fill: • Engine oil
7. Install: • Oil filler cap
8. Inspect:
• Engine (for oil leaks)
• Oil level CHECKING THE OIL PRESSURE
1. Check:
• Oil pressure
Checking steps:
a. Slightly loosen the oil pressure check bolt "1".
b. Start the engine and keep it idling until oil starts to seep from the oil
pressure check bolt. If no oil
comes out after one minute, turn
the engine off so it will not seize.
c. Check oil passages and oil pump
for damage or leakage.
d. Start the engine after solving the problem(s) and recheck the oil
pressure.
e. Tighten the oil pressure check bolt.
ADJUSTING THE ENGINE IDLING
SPEED
• Because the air pressure is lower at
high altitudes, the air-fuel mixture
will become richer. If the engine
idling speed is low, turn the starter
(choke) knob/idling screw a few
clicks counterclockwise to increase
the idling speed.
• Before adjusting the engine idling speed, make sure that the com-
pression pressure is within specifi-
cation and that the air filter element
is not clogged.
• Adjust the engine idling speed with
the starter (choke) knob/idling
screw pushed in completely.
1. Start the engine and warm it up until the engine oil has reached
the specified temperature.
2. Use a temperature probe tester "1" and contact it to the drain bolt
thread.
Recommended brand:
YAMALUBE
Recommended engine
oil type
SAE10W-30, SAE 10W-
40, SAE10W-50, SAE
15W-40, SAE 20W-40 or
SAE 20W-50
Recommended engine
oil grade
API service SG type or
higher, JASO standard
MA
Oil filter element cover:10 Nm (1.0 m•kg, 7.2
ft•lb)
Oil drain bolt (oil pan): 20 Nm (2.0 m•kg, 14
ft•lb)
Oil drain bolt (oil tank): 20 Nm (2.0 m•kg, 14
ft•lb)
Oil quantity: Periodic oil change:0.95 L (0.84 Imp qt,
1.00 US qt)
With oil filter replace-
ment: 1.0 L (0.88 Imp qt, 1.06
US qt)
Total amount: 1.2 L (1.06 Imp qt, 1.27
US qt)
Oil pressure check bolt:
10 Nm (1.0 m•kg, 7.2
ft•lb)
Oil temperature: 55.0–65.0 °C
(131–149°F)

3-25
ELECTRICAL
TROUBLESHOOTING
The following guide for troubleshooting does not cover all the possible causes of problems. If the following problems occur,
perform the specified checks or maintenance jobs. If a problem occurs that is not listed in this manual or if the problem
cannot be corrected by the procedures provided in this manual, contact your Yamaha dealer.
Engine starting problems, engine idling speed problems, and medium and high-speed performance problems
• Engine does not start even though the kickstarter is pushed.
• Engine starts, but soon stops.
Engine idling speed problems
• Engine idling speed fluctuates.
• Engine idling speed is high.
• Engine idling speed is low.
Medium and high-speed performance problems
• Engine speed does not increase.
• Engine knocks.
• Engine speed increases suddenly.
• Loss of engine power.
INSPECTION STEPS
If the aforementioned problems have occurred, perform the following inspection steps in the order given.
Check that the fuel tank is filled with fresh gaso-
line.No good→
Fill the fuel tank.
OK↓
Check that the fuel tank breather hose is not
clogged. (Refer to "INCLUDED PARTS" section
in the CHAPTER 1.)No good→
Repair or replace.
OK↓
Adjusting the engine idling speed(Refer to "AD-
JUSTING THE ENGINE IDLLING SPEED" sec-
tion in the CHAPTER 3.)No good→
Adjust.
OK↓
Check that the fuel hose is connected properly
and is not kinked or pinched.No good→
Repair.
OK↓
Check the spark plug for dirt, the spark plug gap,
and the spark plug cap. (Refer to "CHECKING
THE SPARK PLUG" section in the CHAPTER 3.)No good→
Clean or adjust.
OK↓
Check that the air filter element is installed cor-
rectly and is not clogged. (Refer to "CLEANING
THE AIR FILTER" section in the CHAPTER 3.)No good→
Clean or repair.
OK↓
Checking the sensors, injector and ignition coil
connection.No good→
Repair or replace.
OK↓
Installed condition of ECU (Refer to "CHECKING
THE ECU" section in the CHAPTER 7.)No good→
Repair.
OK↓
Check the assembled condition of the throttle
body, and check the throttle valve and its sur-
rounding parts for dirt.No good→
Repair or clean.
OK↓
Consult a Yamaha dealer.

6-2
FUEL TANK
REMOVING THE FUEL TANK
1. Extract the fuel in the fuel tank through the fuel tank cap with a
pump.
Be careful not to damage the fuel
pump.
2. Remove: • Fuel pump coupler
Although the fuel has been re-
moved from the fuel tank be care-
ful when removing the fuel hoses,
since there may be fuel remaining
in it.
• Before disconnecting the fuel hose, clean the area around the fuel hose
connector.
• Before removing the fuel hose, place a few rags in the area under
where it will be removed.
• To disconnect the fuel hose from the fuel tank, remove the fuel hose
connector holder "a", and then slide
the fuel hose connector cover.
• Slide the fuel hose connector cover "1" in the direction of the arrow
mark, and press the buttons "2" on
both sides of the connector to re-
move the fuel hose.
• Disconnecting the hose is done by hand. There is no need to use tools.
• To prevent sand, dust, and other
foreign material from entering the
fuel pump, install the included fuel
hose joint cover 1 "3" and fuel hose
joint cover 2 "4" onto the fuel pump
and disconnected fuel hose.
3. Remove:•Fuel tank
Do not set the fuel tank down so that
the installation surface of the fuel
pump is directly under the tank.
REMOVING THE FUEL PUMP
1. Remove:•Fuel pump
Do not drop the fuel pump or give
it a strong shock.
CHECKING THE FUEL PUMP
BODY
1. Check:
• Fuel pump bodyCracks/damage → Replace fuel
pump assembly.
CHECKING THE FUEL PUMP
OPERATION
1. Check: • Fuel pump operationRefer to "CHECKING THE FUEL
PRESSURE" section.
INSTALLING THE FUEL PUMP
1. Install: •Fuel pump
• Fuel pump bracket
•Do not damage th e installation
surfaces of the fuel tank when in-
stalling the fuel pump.
• Before installing the fuel pump,
remove any dirt and other foreign
material from the installation sur-
face on the fuel tank.
• Always use a new fuel pump gas- ket.
• Install the lip on the fuel pump gas- ket upward.
• Install the fuel pump as shown in
the illustration.
• Align the projection "a" on the fuel pump with the slot in the fuel pump
bracket. Align the slot "b" on the fuel
tank damper with the projection "a"
on the fuel pump.
• Tighten the fuel pump bolts in stag- es in a crisscross pattern.
INSTALLING THE FUEL TANK
1. Install:•Fuel hose
•When installing the fuel hose,
make sure that it is securely con-
nected, and that the fuel hose
holders are in the correct posi-
tion, otherwise the fuel hose will
not be properly installed.
• Be sure not to kink or pinch the
fuel hose.
• Insert the fuel hose on the fuel pipe
until you hear a definite "click".
• Slide the fuel hose connector cover
"1" at the fuel hose end in the direc-
tion of the arrow.
• Install the fuel hose connector hold-
er "a".
• Make sure that the fuel hose and fuel pump lead are routed through
the guide on the cover.
Fuel pump bracket bolt
4 Nm (0.4 m•kg, 2.9
ft•lb)

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 the spark plug which will not spark.
*marked: Only when the ignition checker is used.
• Remove the following parts before inspection.
1. Seat
2. Fuel tank
• Use the following special tools in this inspection.
Spark gap testSpark→• *Clean or replace spark plug.
• Check the connection of the spark plug cap to the
spark plug.
No spark↓
Check entire ignition system for connection.
(couplers, leads and ignition coil)No good→
Repair or replace.
OK↓
Check engine stop switch. No good→Replace.
OK↓
Check ignition coil. (primary coil and secondary
coil)No good→
Replace.
OK↓
Check AC magneto. (crankshaft position sensor
and stator coil)No good→
Replace.
OK↓
Replace ECU.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754
Pocket tester:
YU-03112-C/90890-03112