Checking The Rectifier/Regulator; Checking The Coolant Temperature Sensor - Yamaha YZ450F Owner's Service Manual

2. Check:
• Stator coil resistance
Out of specification  Replace.
Stator coil resistance
0.624–0.936 
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a. Connect the pocket tester (  1) to the sta-
tor coil coupler.
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
• Positive tester probe 
White "1"
• Negative tester probe 
White "2"
b. Measure the stator coil resistance.
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CHECKING THE RECTIFIER/REGULATOR

EASB111340
1. Check:
• Rectifier/regulator output voltage
Out of specification  Replace.
No load regulated voltage
14.1–14.9 V
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a. Set the digital tachometer to the ignition coil.
Digital tachometer
90890-06760
YU-39951-B
b. Connect the pocket tester (20 VDC) to the
rectifier/regulator coupler.
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
1 2
8-43
ELECTRICAL COMPONENTS
• Positive tester probe 
Red "1"
• Negative tester probe 
Black "2"
W W
c. Start the engine and let it run at about 5000
r/min.
d. Measure the output voltage.
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CHECKING THE COOLANT TEMPERATURE
EASB111341
SENSOR
1. Remove:
• Coolant temperature sensor
EWA
WARNING
• Handle the coolant temperature sensor
with special care.
• Never subject the coolant temperature
sensor to strong shocks. If the coolant
temperature sensor is dropped, replace it.
2. Check:
• Coolant temperature sensor resistance
Out of specification  Replace.
Coolant temperature sensor re-
sistance
2.51–2.78 k at 20°C (68°F)
210–221  at 100°C (212°F)
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a. Connect the pocket tester (  1k/100) to
the coolant temperature sensor.
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
• Positive tester probe 
Green/White "1"
• Negative tester probe 
Black/Blue "2"
B R
2 1