stop start YAMAHA YZ450F 2012 User Guide

6-6
THROTTLE BODY
CHECKING THE INJECTOR
Replace the fuel injector with a
new one if you have dropped or im-
pacted it.
1. Check:
• Injectors
Damage → Replace.
CHECKING THE THROTTLE BODY
•Before removing the throttle
body, clean the area around the
throttle body to prevent dirt and
other foreign material from fall-
ing into the engine.
•If the throttle body is subject to
strong shocks or dropped during
cleaning, replace it.
•Do not use any caustic carbure-
tor cleaning 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". Otherwise, a loss of
performance may occur.
•Do not use compressed air to
clean the throttle body. Other-
wise, foreign material may ad-
here to the intake air pressure
sensor passage "a" and fuel in-
jector "b" in the throttle body.
1. Check:
• Throttle body
Cracks/damage → Replace the
throttle body as a set.
2. Check:
• Starter knob/ idle screw delivery
passages "a"
Obstructions →Blow out with
compressed air.
ASSEMBLING THE THROTTLE
BODY
1. Install:
• O-ring "1"
• Injector "2"
•Bolt "3"
Always use a new O-ring.
INSTALLING THE THROTTLE
BODY
1. Install:
• Throttle body joint "1"
• Throttle body "2"
• Face the slot "a" in the throttle body
joint toward the bottom of the vehi-
cle.
•Align the slot "a" on the throttle body
joint with the projection "b" on the
throttle body.
2. Install the water-resistant cover
"1" onto the throttle body.
CHECKING AND REPLACING THE
PROTECTOR
1. Check:
• Protector "1"
Wear/damage → Replace.
Affix the protector as shown.Bolt (injector)
3 Nm (0.3 kg•m, 2.2
ft•lb)
Throttle body joint clamp
screw
3 Nm (0.3 m•kg, 2.2
ft•lb)

7-4
IGNITION SYSTEM
SPARK GAP TEST
1. Disconnect the spark plug cap
from spark plug.
2. Connect the dynamic spark tester
"1" (ignition checker "2") as
shown.
• Spark plug cap "3"
• Spark plug "4"
A. For USA and CDN
B. Except for USA and CDN
3. Kick the kickstarter crank.
4. Check the ignition spark gap.
5. Start engine, and increase spark
gap until misfire occurs. (for USA
and CDN only)
6. Inspect:
• Sealed portion of spark plug cap
"a"
• Spark plug terminal pin "b"
• Threaded portion of spark plug "c"
7. Inspect:
• Installed condition of spark plug
and spark plug cap
Push in the spark plug cap, mak-
ing sure that it is securely fitted
into the hole in the cylinder head
cover.CHECKING THE COUPLERS AND
LEADS CONNECTION
1. Check:
• Couplers and leads connection
Rust/dust/looseness/short-circuit
→Repair or replace.
CHECKING THE ENGINE STOP
SWITCH
1. Inspect:
• Engine stop switch conduction
Not conductive while it is pushed→
Replace.
Conductive while it is freed→Re-
place.
Set the tester selection position to "Ω
× 1".
CHECKING THE IGNITION COIL
1. Remove the ignition coil cap.
2. Inspect:
• Primary coil resistance
Out of specification→Replace.3. Inspect:
• Secondary coil resistance
Out of specification→Replace.
Disconnect the spark plug cap before
measuring the secondary coil resis-
tance.
CHECKING THE AC MAGNETO
1. Inspect:
• Crankshaft position sensor resis-
tance
Out of specification→Replace.
Minimum spark gap:
6.0 mm (0.24 in)
Tester (+) lead→Black lead "1"
Tester (-) lead→Black lead "2"
Result
Conductive (while the
engine stop switch is
pushed)
Tester (+) lead→Orange lead "1"
Tester (-) lead→Red lead "2"
Primary
coil resis-
tanceTester se-
lector posi-
tion
3.57–4.83
Ω at 20°C
(68°F) Ω × 1
BB
Tester (+) lead→Orange lead "1"
Tester (-) lead→Spark plug termi-
nal "2"
Secondary
coil resis-
tanceTester se-
lector posi-
tion
10.71–14.49
kΩ at 20°C
(68°F) kΩ × 1
Tester (+) lead→Gray lead "1"
Tester (-) lead→Black lead "2"
Crankshaft
position
sensor re-
sistanceTester se-
lector posi-
tion
248–372 Ω
at 20°C
(68°F)Ω × 100
GyB

7-15
FUEL INJECTION SYSTEM
3 Continuity of harness Open or short circuit → Replace.
Between the intake air pressure
sensor coupler and ECU coupler.
(Black/Blue–Black/Blue)
(Pink/White–Pink/White)
(Blue–Blue)Set the switch on the FI di-
agnostic tool sub-wire har-
ness to "ON", and then
check the fault code dis-
play.
Fault code number is not
displayed → Service is
finished.
Fault code number is dis-
played → Refer to item 4.
4 Installed condition of sensor.
Make sure that the installation position is cor-
rect.Check that the sensor is installed
securely and that there are no
pinched leads.Check that the ECU
is installed securely and that there
are no pinched leads.
Incorrect installation → Reinstall
or repair.
Incorrect installation position →
Properly install.Set the switch on the FI di-
agnostic tool sub-wire har-
ness to "ON", and then
check the fault code dis-
play.
Fault code number is not
displayed → Service is
finished.
Fault code number is dis-
played → Refer to item 5.
5 Defective intake air pressure sensor. Execute the diagnostic mode (di-
agnostic code No. D03).
When the engine is stopped,
displays the atmospheric pres-
sure according to the elevation
and weather.
0 m above sea level: Approx.
101 kPa
1000 m above sea level: Ap-
prox. 90 kPa
2000 m above sea level: Ap-
prox. 80 kPa
3000 m above sea level: Ap-
prox. 70 kPa
Check that the value changes
while the engine is being
cranked.
Displayed value is incorrect → Re-
place. Set the switch on the FI di-
agnostic tool sub-wire har-
ness to "ON", and then
check the fault code dis-
play.
Fault code number is not
displayed → Service is
finished.
Fault code number is dis-
played → Refer to item 6.
6 Malfunction in ECU. Replace the ECU. Fault code No. 13
Symptom Intake air pressure sensor signal is not received properly.
Fail-safe system Able to start
Able to drive
Diagnostic code No. D03
FI diagnostic tool display Intake air pressure
Checking method Crank the engine. (If the display value changes, the performance is OK.)
Item Item/components and probable cause Check or maintenance job Checking method

7-16
FUEL INJECTION SYSTEM
If fault code Nos. 13 and 14 are both displayed, perform the checks and maintenance jobs for fault code No. 13 first.
Fault code No. 14
SymptomIntake air pressure sensor system malfunction detected. (clogged hole or disconnected
sensor)
Fail-safe system Able to start
Able to drive
Diagnostic code No. D03
FI diagnostic tool display Intake air pressure
Checking method Crank the engine. (If the display value changes, the performance is OK.)
Item Item/components and probable cause Check or maintenance job Checking method
1 Intake air pressure sensor hose is clogged,
damaged, disconnected, kinked, pinched, or
twisted.Repair or replace. Start the engine and let it
idle for approximately 5
seconds with the throttle
fully closed.
After completing the above
operation, check whether a
fault code number is dis-
played.
Fault code number is not
displayed → Service is
finished.
Fault code number is dis-
played → Refer to item
2.
2 Defective intake air pressure sensor. Execute the diagnostic mode (di-
agnostic code No. D03).
When the engine is stopped,
displays the atmospheric pres-
sure according to the elevation
and weather.
0 m above sea level: Approx.
101 kPa
1000 m above sea level: Ap-
prox. 90 kPa
2000 m above sea level: Ap-
prox. 80 kPa
3000 m above sea level: Ap-
prox. 70 kPa
Display value does not change→
Replace the sensor.

7-24
FUEL INJECTION SYSTEM
5 Defective atmospheric pressure sensor. Execute the diagnostic mode (di-
agnostic code No. D02).
When the engine is stopped,
displays the atmospheric pres-
sure according to the elevation
and weather.
0 m above sea level: Approx.
101 kPa
1000 m above sea level: Ap-
prox. 90 kPa
2000 m above sea level: Ap-
prox. 80 kPa
3000 m above sea level: Ap-
prox. 70 kPa
Displayed value is incorrect → Re-
place.Set the switch on the FI di-
agnostic tool sub-wire har-
ness to "ON", and then
check the fault code dis-
play.
Fault code number is not
displayed → Service is
finished.
Fault code number is dis-
played → Refer to item 6.
6 Malfunction in ECU. Replace the ECU. Fault code No. 23
Symptom Atmospheric pressure sensor signal is not received properly.
Fail-safe system Able to start
Able to drive
Diagnostic code No. D02
FI diagnostic tool display Atmosphere
Checking method Measure the atmospheric pressure.
Item Item/components and probable cause Check or maintenance job Checking method

7-37
ELECTRICAL COMPONENTS
3. Connect the FI diagnostic tool
sub-wire harness to a battery, and
then set the switch on the harness
to "ON".
When checking the atmospheric
pressure sensor, do not start the
engine.
4. Measure the atmospheric pres-
sure sensor output voltage.
Out of specification→Replace.
CHECKING THE RECTIFIER/
REGULATOR
1. Connect:
• Connect the tester to the coupler
for connecting optional part
Tester (+) lead→ Red lead "1"
Tester (-) lead→ Black/White lead
"2"
2. Start the engine.
3. Check:
• Rectifier/regulato output voltage
Out of specification → Replace.
4. Stop the engine.CHECKING THE FUEL INJECTORS
1. Remove:
•Seat
•Fuel tank
• Air filter case
2. Check:
•Injector resistance
3. Connect:
•Tester
Tester (+) lead → Injector termi-
nal "1"
Tester (-) lead → Injector termi-
nal "2"
Out of specification→Replace. Test harness S–pressure
sensor (3P):
YU-03207/90890-03207
Output volt-
ageTester se-
lector posi-
tion
3.4–3.8 V DCV
Output volt-
ageTester se-
lector posi-
tion
14.1–14.9 V DCV
Lg
R
B/W
Injector re-
sistanceTester se-
lector posi-
tion
12.0 Ω
(20°C, 68°F) Ω×10