Yamaha YP125R Service Manual

ELECTRICAL COMPONENTS
8-87
EAS28240
CHECKING THE SPEED SENSOR
1. Check:
• Speed sensor output voltage
Out of specification → Replace.
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a. Connect the pocket tester (DC 20 V) to the
speed sensor coupler (wire harness end) as
shown.
b. Set the main switch to “ON”.
c. Elevate the front wheel and slowly rotate it.
d. Measure the voltage of gray and gray/black.
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.
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EAS28250
CHECKING THE RADIATOR FAN MOTOR
1. Check:
• Radiator fan motor
Faulty/rough movement → Replace.
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a. Disconnect the radiator fan motor coupler
from the wire harness.
b. Connect the battery (DC 12 V) as shown.
c. Measure the radiator fan motor movement.
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EAS28260
CHECKING THE COOLANT TEMPERATURE
SENSOR
1. Remove:
• Coolant temperature sensor
Refer to “CYLINDER HEAD (YP125R)” on
page 5-7 and “CYLINDER HEAD (YP250R)”
on page 5-67.
WARNING
EWA14130
• Handle the coolant temperature sensor
with special care.
• Never subject the coolant temperature sen-
sor to strong shocks. If the coolant temper-
ature sensor is dropped, replace it.
2. Check:
• Coolant temperature sensor resistance
Out of specification → Replace.
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a. Connect the pocket tester (Ω × 1k/× 100) to
the coolant temperature sensor terminals as
shown.
b. Immerse the coolant temperature sensor “1”
in a container filled with coolant “2”.
T
IP
Make sure the coolant temperature sensor ter-
minals do not get wet.
c. Place a thermometer “3” in the coolant.
Output voltage reading cycle
0.6 V to 4.8 V to 0.6 V to 4.8 V
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
• Positive tester probe →
gray “1”
• Negative tester probe →
gray/black “2”
• Positive tester probe →
red “1”
• Negative tester probe →
black “2”
Gy
P
B/W
O/R
Gy/B
Gy/R
1
2
Coolant temperature sensor re-
sistance
2.32–2.59 kΩ at 20 °C (68 °F)
310–326 Ω at 80 °C (176 °F)
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C

Yamaha YP125R Specifications

General

Engine Type	Liquid-cooled, 4-stroke, SOHC, 4-valve
Bore x Stroke	52.4 mm x 57.9 mm
Fuel System	Fuel Injection
Ignition System	TCI
Transmission	V-Belt Automatic
Front Suspension	Telescopic fork
Rear Suspension	Unit Swing
Front Brake	Hydraulic single disc, Ø267 mm
Starter System	Electric
Rear Tyre	140/70-14M/C 62P (Tubeless)