Yamaha YZF-R125 Service Manual: Checking the speed sensor

1. Check:

Speed sensor output voltage Out of specification → Replace.


a. Connect the pocket tester (DC 20 V) to the speed sensor coupler (wire harness end) as shown.


  • Positive tester probe gray "1"
  • Negative tester probe gray/black "2"

Checking the speed sensor


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 V to 5.0 V to 0 V to 5.0 V.

    Checking the fuel sender
    1. Drain the fuel from the fuel tank. 2. Check: Fuel sender resistance Out of specification → Replace the fuel sender. a. Connect the pocket tester ( × 10) to the fuel sender c ...

    Checking the radiator fan motor
    1. Check: Radiator fan motor Faulty/rough movement → Replace. a. Disconnect the radiator fan motor coupler from the wire harness. b. Connect the battery (DC 12 V) as shown. Posi ...

    Other materials:

    Installing the relay arm
    1. Lubricate: Spacers Bearings Oil seals Bolts (unthreaded shaft portion only) 2. Install: Bearing "1" (to the relay arm) Oil seal "2" (to the relay arm) 3. Rear shock absorber assembly 4. Relay arm 5. Connecting arm A. Left side B. Right side ...

    Catalytic converters
    This vehicle is equipped with catalytic converters in the exhaust system. WARNING The exhaust system is hot after operation. To prevent a fire hazard or burns: Do not park the vehicle near possible fire hazards such as grass or other materials that easily burn. Park the vehic ...

    Adjusting the clutch cable free play
    1. Check: Clutch cable free play "a" Out of specification Adjust. 2. Adjust: Clutch cable free play a. Pull back the rubber cover "1" b. Loosen the locknut "2". c. Turn the adjusting bolt "3" in direction "a" or "b" until the specified clutch cable free play is obtained. ...

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