2012 YAMAHA YZ450F fuel

3-9
ENGINE
8. Apply:
• Foam-air-filter oil or equivalent oil
to the element
Squeeze out the excess oil. Element
should be wet but not dripping.
9. If the thin sheet (air filter element
2) is dirty with mud etc., clean the
thin sheet (air filter element 2) by
the following steps.
Cleaning steps:
a. Remove the air filter element 2
"1".
b. Clean the air filter element 2 with
solvent.
After cleaning, remove the remaining
solvent by squeezing the element.
Do not twist the element when
squeezing the element.
c. Inspect the air filter element 2.
Damage → Replace.
d. Install the air filter element 2.
10. Install:
• Air filter element "1"
• Air filter guide "2"
•Binder
11. Install:
• Mounting bolt for air filter case
cover12. Install:
• Fuel tank bolt (front)
CHECKING THE THROTTLE BODY
JOINT
1. Remove:
•Seat
• Air scoop (left/right)
•Fuel tank
• Air filter
2. Check:
• Throttle body joint "1"
Cracks/damage → Replace.
3. Install:
• Air filter
•Fuel tank
• Air scoop (left/right)
•Seat
CHECKING THE FUEL LINE
1. Remove:
•Seat
•Fuel tank
• Air scoop (left/right)
• Air filter case
• Cover
2. Check:
• Fuel hose "1"
Cracks/damage → Replace.
Loose connection → Reconnect.
3. Install:
• Cover
• Air filter case
• Air scoop (left/right)
•Fuel tank
•Seat
CHECKING THE ENGINE OIL
LEVEL
1. Stand the machine on a level sur-
face.
• When checking the oil level make
sure that the machine is upright.
• Place the machine on a suitable
stand.
2. Start the engine, warm it up for
2–3 minutes at engine idling
speed, and then stop the engine
and wait approximately 1 minute.
3. Inspect:
• Oil level
Make sure that the engine oil level
is between the maximum level
line "a" and minimum level line "b"
shown for the oil level check win-
dow.
Above the upper limit "a"→Check
that no oil comes out when the
check bolt "1" for the oil quantity
upper limit is removed.
If any engine oil comes out, drain
it until its last drop is out.
Below the level mark "b"→Add
sufficient oil and idle run the en-
gine, and after stopping the en-
gine, recheck through the oil
inspection window that the oil is at
the specified level.
• Check the oil quantity within 5 min-
utes after the engine is shut off.
Over 5 minutes, idle the engine
again and recheck the oil quantity.
• Do not leave the check bolt for the
oil quantity upper limit removed.
Otherwise, the oil level drops with
time in the engine, allowing the oil
to flow out.
• Engine oil also luburicates the
clutch and the wrong oil types or
additives could cause clutch
slippage. Therefore, do not add
any chemical additives or use en-
gine oils with a grade of CD or
higher and do not use oils la-
beled "ENERGY CONSERVING
II".
• Do not allow foreign material to
enter the crankcase.
Oil application quantify:
35 g
Mounting bolt for air filter
case cover:
5 Nm (0.5 m•kg, 3.6
ft•lb)
Fuel tank bolt (front):
9 Nm (0.9 m•kg, 6.5
ft•lb)

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 levelCHECKING 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)

3-11
ENGINE
3. Adjust:
• Engine idling speed
Adjustment steps:
a. Turn the starter knob/idle screw
"1" until the specified engine idling
speed is obtained.
Using the digital tachometer, mea-
sure the engine speed with the detec-
tor "c" pinched in the high tension
cord "2" of the ignition coil.
ADJUSTING THE VALVE
CLEARANCE
• This section is intended for those
who have basic knowledge and skill
concerning the servicing of Yama-
ha motorcycles (e.g., Yamaha deal-
ers, service engineers, etc.) Those
who have little knowledge and skill
concerning servicing are requested
not to undertake inspection, adjust-
ment, disassembly, or reassembly
only by reference to this manual. It
may lead to servicing trouble and
mechanical damage.
• The valve clearance should be ad-
justed when the engine is cool to
the touch.
1. Remove:
•Seat
Refer to "SEAT AND SIDE COV-
ERS" section in the CHAPTER 4.
•Fuel tank
Refer to "FUEL TANK" section in
the CHAPTER 6.
2. Remove:
• Spark plug
• Cylinder head cover
Refer to "CAMSHAFTS" section
in the CHAPTER 4.
3. Remove:
• Timing mark accessing screw "1"
• Crankshaft end accessing screw
"2"
• O-ring
4. Check:
• Valve clearance
Out of specification→Adjust.
Checking steps:
a. Turn the crankshaft counterclock-
wise with a wrench.
b. Align the alignment mark "a" on
the rotor with the alignment mark
"b" on the crankcase cover.
Make sure that the alignment mark
"c" on the exhaust camshaft sprocket
and the alignment mark "d" on the in-
take camshaft sprocket are aligned
with the edge of the cylinder head.
c. Measure the valve clearance "e"
using a feeler gauge "1".
Record the measured reading if the
clearance is incorrect.
Digital tachometer:
YU-39951-B/90890-
06760
To increase the engine idling
speed→Turn the starter
(choke) knob/idling screw
counterclockwise "a".
To decrease the engine idling
speed→Turn the starter
(choke) knob/idling screw
clockwise "b".
Engine idling speed:
1,900–2,100 r/min
Valve clearance (cold):
Intake valve:
0.10–0.15 mm
(0.0039–0.0059 in)
Exhaust valve:
0.20–0.25 mm
(0.0079–0.0098 in)

3-22
CHASSIS
e. Loosen the steering ring nut one
turn.
f. Retighten the steering ring nut us-
ing the steering nut wrench.
Avoid over-tightening.
g. Check the steering stem by turn-
ing it lock to lock. If there is any
binding, remove the steering stem
assembly and inspect the steer-
ing bearings.
h. Install the washer "5", upper
bracket "6", steering stem nut "7",
handlebar "8", handlebar upper
holder "9" and number plate "10".
• Apply the lithium soap base grease
on the contact surface of the steer-
ing stem nut when installing.
• The handlebar upper holder should
be installed with the punched mark
"a" forward.
• Install the handlebar so that the
marks "b" are in place on both
sides.
• Install the handlebar so that the pro-
jection "c" of the handlebar upper
holder is positioned at the mark on
the handlebar as shown.
• Insert the end of the fuel breather
hose "11" into the hole in the steer-
ing stem.
First tighten the bolts on the front
side of the handlebar upper holder,
and then tighten the bolts on the
rear side.
Steering ring nut (final
tightening):
7 Nm (0.7 m•kg, 5.1
ft•lb)
Steering stem nut:
145 Nm (14.5 m•kg, 105
ft•lb)
Handlebar upper holder:
28 Nm (2.8 m•kg, 20
ft•lb)
Pinch bolt (upper brack-
et):
21 Nm (2.1 m•kg, 15
ft•lb)
Number plate:
7 Nm (0.7 m•kg, 5.1
ft•lb)

3-24
ELECTRICAL
ELECTRICAL
CHECKING THE SPARK PLUG
1. Remove:
• Spark plug
2. Inspect:
• Electrode "1"
Wear/damage→Replace.
• Insulator color "2"
Normal condition is a medium to
light tan color.
Distinctly different color→Check
the engine condition.
An extended run at low speeds
causes the insulator to be colored
black even if the air-fuel mixture is
normal.
3. Measure:
• Plug gap "a"
Use a wire gauge or thickness
gauge.
Out of specification→Regap.
4. Clean the plug with a spark plug
cleaner if necessary.
5. Tighten:
• Spark plug
• Before installing a spark plug, clean
the gasket surface and plug sur-
face.
• Finger-tighten "a" the spark plug
before torquing to specification "b".
CHECKING THE IGNITION TIMING
1. Remove:
• Timing mark accessing screw "1"
2. Attach:
• Timing light
• Digital tachometer
To the ignition coil lead (orange
lead "1").
3. Adjust:
• Engine idling speed
Refer to "ADJUSTING THE EN-
GINE IDLING SPEED" section.
4. Check:
• Ignition timing
Visually check the stationary
pointer "a" is within the firing
range "b" on the rotor.
Incorrect firing range→Check ro-
tor and Crankshaft position sen-
sor.
5. Install:
• Timing mark accessing screw Spark plug gap:
0.7–0.8 mm
(0.028–0.031 in)
Spark plug:
13 Nm (1.3 m•kg, 9.4
ft•lb)
Timing light:
YM-33277-A/90890-
03141
Timing mark accessing
screw:
6 Nm (0.6 m•kg, 4.3
ft•lb)

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.

4-5
RADIATOR
RADIATOR
REMOVING THE RADIATOR
Order Part name Q'ty Remarks
Drain the coolant.Refer to "CHANGING THE COOLANT" sec-
tion in the CHAPTER 3.
SeatRefer to "SEAT AND SIDE COVERS" sec-
tion.
Fuel tank Refer to "FUEL TANK" section in the CHAP-
TER 6.
Air filter caseRefer to "THROTTLE BODY" section in the
CHAPTER 6.
1 Radiator guard 2
2 Radiator hose clamp 8 Only loosening.
3 Right radiator 1
4 Radiator hose 2 1
5 Radiator hose 4 1
6 Radiator hose 3 1
7 Pipe 2/O-ring 1/1
8 Radiator breather hose 1
9 Left radiator 1
10 Radiator hose 1 1

4-8
CAMSHAFTS
CAMSHAFTS
REMOVING THE CYLINDER HEAD COVER
Order Part name Q'ty Remarks
Seat Refer to "SEAT AND SIDE COVERS" sec-
tion.
Fuel tank Refer to "FUEL TANK" section in the CHAP-
TER 6.
CoverRefer to "THROTTLE BODY" section in the
CHAPTER 6.
1 Spark plug 1
2 Cylinder head breather hose 1
3 Bolt (cylinder head cover) 3
4 Cylinder head cover 1
5 Cylinder head cover gasket 1
6 Timing chain guide (top side) 1