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 camshaft and rocker arms
    1. Lubricate: Rocker arms Rocker arm shafts 2. Lubricate: Camshaft 3. Install: Camshaft "1" NOTE: Make sure that the camshaft projections "a" and hole "b" are positioned as shown in the illustration. 4. Install: Rocker arms Rocker arm shafts "1" NOTE: Make ...

    Checking the friction plates
    The following procedure applies to all of the friction plates. 1. Check: Friction plate Damage/wear Replace the friction plates as a set. 2. Measure: Friction plate thickness Out of specification Replace the friction plates as a set. NOTE: Measure the friction plate ...

    Checking the steering head
    1. Wash: Bearings Bearing races 2. Check: Bearings Bearing races Damage/pitting →Replace. 3. Replace: Bearings Bearing races a. Remove the bearing races from the steering head pipe with a long rod "1" and hammer. b. Remove the bearing race from the lower bracket ...

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