2008 YAMAHA WR 450F Owners Manual

7-16
THROTTLE POSITION SENSOR SYSTEM
HANDLING NOTE
Do not loosen the screw (throttle
position sensor) "1" except when
changing the throttle position sen-
sor due to failure because it will
cause a drop in engine perfor-
mance.
CHECKING THE COUPLERS AND
LEADS CONNECTION
1. Check:
• Couplers and leads connection
Rust/dust/looseness/short-circuit
→Repair or replace.
CHECKING THE THROTTLE
POSITION SENSOR COIL
1. Inspect:
• Throttle position sensor coil resis-
tance
Out of specification→Replace.
2. Loosen:
• Throttle stop screw "1"
Turn out the throttle stop screw until
the throttle shaft is in the full close po-
sition.
3. Inspect:
• Throttle position sensor coil vari-
able resistance
Check that the resistance in in-
creased as the throttle grip is
moved from the full close position
to the full open position.
Out of specification→Replace.
CHANGING AND ADJUSTING THE
THROTTLE POSITION SENSOR
1. Remove:
• Throttle position sensor coupler
• Carburetor
2. Remove:
• Screw (throttle position sensor)
"1"
• Throttle position sensor "2"
Loosen the screw (throttle position
sensor) using the T25 bit.
3. Replace:
• Throttle position sensor
4. Install:
• Throttle position sensor "1"
• Screw (throttle position sensor)
"2"
• Align the slot "a" in the throttle posi-
tion sensor with the projection "b"
on the carburetor.
• Temporarily tighten the screw
(throttle position sensor).
5. Install:
•Carburetor
• Throttle position sensor coupler
6. Adjust:
• Engine idling speed
Refer to "ADJUSTING THE EN-
GINE IDLING SPEED" section in
the CHAPTER 3.
7. Insert the thin electric conductors
"2" (lead) into the throttle position
sensor coupler "1", as shown, and
connect the tester to them.
• Do not insert the electric conduc-
tors more than required because
it may reduce the waterproof
function of the coupler.
• Make sure that a short-circuit
does not develop between the
terminals because it may cause
damage to electrical compo-
nents.
8. Start the engine.
9. Adjust:
• Throttle position sensor output
voltage
Adjustment steps:
a. Adjust the installation angle of the
throttle position sensor "1" to ob-
tain the specified output voltage. Tester (+) lead→Blue lead "1"
Tester (-) lead→Black lead "2"
Throttle po-
sition sen-
sor coil
resistanceTester se-
lector posi-
tion
4–6 kΩ at
20°C (68 °F) kΩ×1
Tester (+) lead→Yellow lead "1"
Tester (-) lead→Black lead "2"
Throttle position
sensor coil vari-
able resistanceTester
selec-
tor po-
sition
Full
closedFull
opened
kΩ×1 Zero –2
kΩat
20°C
(68 °F)4–6
kΩat
20 °C
(68 °F)
Tester (+) lead→Yellow lead "3"
Tester (-) lead→Black lead "4"

7-17
THROTTLE POSITION SENSOR SYSTEM
Measure the output voltage accurate-
ly with a digital electronic voltmeter
that gives an easy reading of a small
voltage.
10. Put the aligning marks "a" on the
throttle position sensor and car-
buretor.
11. Stop the engine.
12. Remove the carburetor.
13. Tighten:
• Screw (throttle position sensor)
"1"
Tighten the screw (throttle position
sensor) using the T25 bit.
14. Install the carburetor.CHECKING THE THROTTLE
POSITION SENSOR INPUT
VOLTAGE
1. Disconnect the throttle position
sensor coupler.
2. Start the engine.
3. Inspect:
• Throttle position sensor input volt-
age
Out of specification→Replace the
CDI unit. Throttle po-
sition sen-
sor output
voltageTester se-
lector posi-
tion
0.58–0.78 V DCV
Tester (+) lead→Blue lead "1"
Tester (-) lead→Black/Blue lead
"2"
Throttle po-
sition sen-
sor input
voltage Tester se-
lector posi-
tion
4–6 V DCV-20

7-18
LIGHTING SYSTEM
LIGHTING SYSTEM
INSPECTION STEPS
Refer to the following flow chart when inspecting the lighting system for possible problems.
• Remove the following parts before inspection.
1. Seat
2. Fuel tank
3. Left side cover
• Use the following special tools in this inspection.
Check the bulb and bulb socket. No good→Replace the bulb and/or bulb socket.
OK↓
Check the taillight (LEDs). No good→Replace the taillight assembly.
OK↓
Check the AC magneto. (Lighting coil) No good→Replace.
OK↓
Check the entire lighting system proper for con-
nections.Improperly
connected→Repair or replace.
OK↓
Check the rectifier/regulator. (Out-put voltage) No good→Replace.
Pocket tester:
YU-3112-C/90890-03112

7-19
LIGHTING SYSTEM
CHECKING THE TAILLIGHT
(LEDs)
1. Disconnect the taillight coupler.
2. Connect two jumper leads "1"
from the battery terminals to the
respective coupler terminal as
shown.
3. Check:
• LED (for proper operation)
Does not light→Replace the tail-
light assembly.
• A wire that is used as a jumper
lead must have at least the same
capacity of the battery lead, oth-
erwise the jumper lead may burn.
• This check is likely to produce
sparks, therefore, make sure no
flammable gas or fluid is in the
vicinity.
CHECKING THE AC MAGNETO
1. Inspect:
• Lighting coil resistance
Out of specification→Replace.CHECKING THE RECTIFIER/
REGULATOR
1. Connect the battery leads.
2. Start the engine.
3. Turn on the headlight and taillight
by turning on the light switch.
4. Inspect:
• Out-put voltage
Out of specification→Replace
rectifier/regulator. Battery (+) terminal→Blue lead
"2"
Battery (-) terminal→Black lead
"3"
Tester (+) lead→Yellow lead "1"
Tester (-) lead→Ground "2"
Light-
ing coil
resis-
tanceTester selector
position
0.224–
0.336 Ω
at 20 °C
(68 °F) Ω × 1
Tester (+) lead→Yellow lead "1"
Tester (-) lead→Black lead "2"
Out-put
voltageTester se-
lector posi-
tion
12.5–13.5 V
at 5,000 r/
minACV-20

7-20
SIGNALING SYSTEM
SIGNALING SYSTEM
INSPECTION STEPS
If the speedometer will not operate, use the following inspection steps.
*1 marked: Refer to "CHECKING AND CHARGING THE BATTERY" section in the CHAPTER 3.
• Remove the following parts before inspection.
1. Headlight
• Use the following special tools in this inspection.
*1 Check battery. No good→Recharge or replace.
OK↓
Check each coupler and wire connection. No good→Repair or replace.
OK↓
Check multi-function display. (Input voltage) No good→Replace wire harness.
OK↓
Check multi-function display. (Output voltage) No good→Replace multi-function display.
OK↓
Check speed sensor. No good→Replace.
Pocket tester:
YU-3112-C/90890-03112

7-21
SIGNALING SYSTEM
CHECKING THE COUPLERS AND
LEADS CONNECTION
1. Check:
• Couplers and leads connection
Rust/dust/looseness/short-circuit
→Repair or replace.
CHECKING THE MULTI-FUNCTION
DISPLAY INPUT VOLTAGE
1. Disconnect the multi-function dis-
play coupler.
2. Set the main switch to "ON".
3. Measure:
• Multi-function display input volt-
age
Out of specification→Replace
wire harness.
Make sure that a short-circuit does
not develop between the terminals
because it may cause damage to
electrical components.
CHECKING THE MULTI-FUNCTION
DISPLAY OUTPUT VOLTAGE
1. Disconnect the multi-function dis-
play coupler.
2. Set the main switch to "ON".
3. Measure:
• Multi-function display output volt-
age
Out of specification→Replace
multi-function display.
Make sure that a short-circuit does
not develop between the terminals
because it may cause damage to
electrical components.
CHECKING THE SPEED SENSOR
OUTPUT VOLTAGE
1. Insert the thin electric conductors
"1" (lead) into the speed sensor
coupler "2", as shown, and con-
nect the tester to them.
• Do not insert the electric conduc-
tors more than required because
it may reduce the waterproof
function of the coupler.
• Make sure that a short-circuit
does not develop between the
terminals because it may cause
damage to electrical compo-
nents.
2. Set the main switch to "ON".
3. Measure:
• Speed sensor output voltage
Output voltage not correct→Re-
place the speed sensor.
Measurement steps:
a. Elevate the front wheel and slowly
rotate it.
b. Measure the voltage (DCV) of
white lead and black lead. With
each full rotation of the front
wheel, the voltage reading should
cycle from 0.6 V to 4.8 V to 0.6 V
to 4.8 V.
Tester (+) lead→Brown lead "1"
Tester (-) lead→Black lead "2"
Multi-func-
tion dis-
play input
voltageTester se-
lector posi-
tion
10 V or
moreDCV-20
Tester (+) lead→Red lead "1"
Tester (-) lead→Black/White lead
"2"
Multi-func-
tion dis-
play output
voltageTester se-
lector posi-
tion
4.5 V or
moreDCV-20
Tester (+) lead→White lead "3"
Tester (-) lead→Black lead "4"

PRINTED IN JAPAN
(E) PRINTED ON RECYCLED PAPER YAMAHA MOTOR CO., LTD.
2500 SHINGAI IWATA SHIZUOKA JAPAN