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:

    Checking and lubricating the brake and shift pedals
    Brake pedal Brake pedal Shift pedal Shift pedal The operation of the brake and shift pedals should be checked before each ride, and the pedal pivots should be lubricated if necessary. Recommended lubricant:Lithium-soap-based grease ...

    Installing the swingarm
    1. Lubricate: Bearings Spacers Dust covers Pivot shaft 2. Install: Bearings "1" 2. Swingarm A. Left side B. Right side 3. Install: Swingarm adjusting collar "1" Swingarm "2" Pivot shaft Pivot shaft nut "3" a. Install, and then fully turn in the swingarm adju ...

    Checking the front brake lever free play
    Checking the front brake lever free play Brake lever free play The brake lever free play should measure 2.0-5.0 mm (0.08-0.20 in) as shown. Periodically check the brake lever free play and, if necessary, have a Yamaha dealer check the brake system. WARNING An incorrect brake le ...

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