2011 YAMAHA YZ450F ignition

2-23
CABLE ROUTING DIAGRAM
1. Tension pipe
2. Coolant temperature sensor
coupler
3. Front engine bracket
4. Fuel pump coupler
5. Fuel pump
6. Intake air temperature sensor
coupler
7. Radiator hose 2
8. Radiator breather hose
9. Radiator hose 1
10. Radiator hose 4
11. Radiator pipe 2
12. Radiator hose 3
13. Cylinder head breather hose
14. Frame
15. ECU (electronic control unit)
16. ECU bracket
17. Main harness
18. AC magneto lead
19. Throttle position sensor lead
20. Condenser lead
21. Coolant temperature sensor
lead
22. Ignition coil lead
23. CondenserA. Fasten the wire harness at the
positioning tape to the ECU
bracket with a plastic locking tie.
Face the buckle of the plastic
locking tie downward, and then
cut off the excess end of the tie.
B. Install the cover onto the wire
harness coupler.
C. Route the condenser lead, throt-
tle position sensor lead, coolant
temperature sensor lead, igni-
tion coil lead, and AC magneto
lead under radiator hose 2.
D. Connect the vacuum hose to the
atmospheric pressure sensor,
and then fasten the hose with
the clamp. Make sure to face the
moving part of the sensor rear-
ward.
E. After connecting the condenser
coupler, install the coupler cover
onto the coupler.
F. After connecting the throttle po-
sition sensor coupler, install the
coupler cover onto the coupler.
G. Fasten the AC magneto lead,
condenser lead, throttle position
sensor lead, coolant tempera-
ture sensor lead, and ignition
coil lead to the frame with the
plastic band, making sure to po-
sition the band between the igni-
tion coil bracket and the tension
pipe. Face the buckle of the
plastic band to the right with the
end pointing rearward.
H. Point the end of the vacuum
hose rearward.
I. Fit the bracket into the hole in
the rubber portion of the con-
denser.
J. Fasten the radiator breather
hose to the frame with the plas-
tic band, making sure to position
the band above the front engine
bracket. Face the buckle of the
plastic band outward with the
end pointing rearward.
K. After connecting the coolant
temperature sensor coupler, in-
stall the coupler cover onto the
coupler.L. Route the radiator breather hose
between the down tubes.
M. Fasten the fuel hose and fuel
pump lead with the plastic band,
making sure to position the band
between the bend in the fuel
hose protector and the end of
the protector. Point the end of
the plastic band upward.
N. Insert the projection on the joint
coupler into the hole in the
bracket, and then install the cou-
pler cover onto the coupler.
O. Route the atmospheric pressure
sensor lead, intake air pressure
sensor lead, intake air tempera-
ture sensor lead, fuel injector
lead, and fuel pump lead above
radiator hose 2. Position the
joint coupler above radiator
hose 2.
P. Route the radiator breather hose
to the inside of radiator hose 1
and the front engine bracket.
Q. Hose installation position
(1.3–3.3 mm, 0.05–0.13 in)
R. Clip installation position (0–2.0
mm, 0–0.08 in)
S. Install the washer so that it con-
tacts the bolt head.
T. Install the collar so that the
flange on the collar contacts the
ECU bracket.

2-24
CABLE ROUTING DIAGRAM
1. Ignition coil coupler
2. Coolant temperature sensor
lead
3. Atmospheric pressure sensor
coupler
4. Intake air temperature sensor
lead
5. Clamp
6. Intake air pressure sensor cou-
pler
7. Cover8Fuel hose
9. Fuel pump lead
10. Fuel injector coupler
11. Throttle body
12. High tension code
13. Throttle cable
14. AC magneto leadA. Route the fuel pump lead to the
outside of the fuel hose and
above the cover.
B. Route the spark plug wire be-
tween the throttle cables and the
throttle body. When installing
the air filter, be sure not to pinch
the spark plug wire.
C. Route the AC magneto lead to
the inside of the throttle cables.

3-5
PRE-OPERATION INSPECTION AND MAINTENANCE
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.
GENERAL INSPECTION AND MAINTENANCE
Item Routine Page
CoolantCheck that coolant is filled up to the radiator cap. Check the cool-
ing system for leakage.P.3-6 – 7
FuelCheck that a fresh gasoline is filled in the fuel tank. Check the fuel
line for leakage.P.1-17
Engine oilCheck that the oil level is correct. Check the crankcase and oil line
for leakage.P.3-9 – 10
Gear shifter and clutchCheck that gears can be shifted correctly in order and that the
clutch operates smoothly.P.3-7
Throttle grip/HousingCheck that the throttle grip operation and free play are correctly
adjusted. Lubricate the throttle grip and housing, if necessary.P.3-8
Brakes Check the play of front brake and effect of front and rear brake. P.3-14 – 17
Drive chainCheck drive chain slack and alignment. Check that the drive chain
is lubricated properly.P.3-17 –18
WheelsCheck for excessive wear and tire pressure. Check for loose
spokes and have no excessive play.P.3-21
SteeringCheck that the handlebar can be turned smoothly and have no ex-
cessive play.P.3-21 – 22
Front forks and rear shock
absorberCheck that they operate smoothly and there is no oil leakage.
P.3-18 – 20
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 pipe Check that the exhaust pipe is tightly mounted and has no cracks. P.4-3 – 6
Rear wheel sprocket Check that the rear wheel sprocket tightening bolt is not loose. P.3-17
Lubrication Check for smooth operation. Lubricate if necessary. P.3-23
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P.1-19
Lead connectorsCheck that the AC magneto, ECU and ignition coil are connected
tightly.P.1-10 – 11
SettingsIs the machine set suitably for the condition of the racing course
and weather or by taking into account the results of test runs be-
fore racing? Are inspection and maintenance completely done?P.8-1 – 5

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 in spection, 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 coverRefer to "CAMSHAFTS" section
in the CHAPTER 4.
3. Remove: • Timing mark accessing screw "1"
• Crankshaft end accessing screw "2"
• O-ring
4. Check: • Valve clearanceOut 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)

3-24
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.

4-47
ENGINE REMOVAL
ENGINE REMOVAL
REMOVING THE ELECTRONIC PARTS
Order Part name Q'ty Remarks
Hold the machine by placing the suitable stand
under the frame.Refer to "HANDLING NOTE".
SeatRefer to "SEAT AND SIDE COVERS" sec-
tion.
Fuel tankRefer to "FUEL TANK" section in the CHAP-
TER 6.
Air filter caseRefer to "THROTTLE BODY" section in the
CHAPTER 6.
Radiator Refer to "RADIATOR" section.
1 Rectifier/regulator 1
2 Ignition coil bracket 1
3 Ignition coil 1
4 Atmospheric pressure sensor 1
5 Condenser 1
6 AC magneto lead 1 Disconnect.
7 Coolant temperature sensor coupler 1 Disconnect.

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, service engineers, etc.) Those who have little knowledge and skill concerning servicing are request-
ed not to undertake inspection, adjustment, disassembly, or reassembly only by reference to this manual. It may lead to
servicing trouble and mechanical damage.
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
ELECTRICAL COMPONENTS
1. Crankshaft position sensor
2. AC magneto
3. Rectifier/regulator
4. Condenser
5. Fuel pump
6. Engine stop switch
7. ECU
8. Ignition coil9. Spark plug
10. Fuel injector
11. Intake air temperature sensor
12. Intake air pressure sensor
13. Throttle position sensor
14. Atmospheric pressure sensor
15. Coolant temperature sensor
16. Coupler for connecting optional part
7