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:

    Starting failures
    Engine 1. Cylinder and cylinder head - Loose spark plug - Loose cylinder head or cylinder - Damaged cylinder head gasket - Damaged cylinder gasket - Worn or damaged cylinder - Incorrect valve clearance - Improperly sealed valve - Incorrect valve-to-valve-seat contact - Incorrect valve timi ...

    Troubleshooting
    Any of the following fail to light: headlight, high beam indicator light, taillight, license plate light, auxiliary light or meter light. NOTE: Before troubleshooting, remove the following part(s): 1. Seats 2. Fuel tank ...

    Assembling the main axle and drive axle
    1. Install: Toothed washer "1" Circlip "2" NOTE: Be sure to install the circlip so that its sharp edge "a" is facing away from the toothed washer and gear. Be sure the circlip ends "b" are positioned at the axle spline groove "c". 2. Install: 2nd pinion gear "1" NO ...

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