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:

    Removing the rear brake master cylinder
    NOTE: Before removing the rear brake master cylinder, drain the brake fluid from the entire brake system. 1. Disconnect: Rear brake light switch coupler 2. Loosen: Rear brake light switch "1" 3. Remove: Rear brake master cylinder bolts Rear brake master cylinder 4. Remove: ...

    Checking the condition of the bulb sockets
    The following procedure applies to all of the bulb sockets. 1. Check: Bulb socket (for continuity) (with the pocket tester) No continuity Replace. NOTE: Check each bulb socket for continuity in the same manner as described in the bulb section, however, note the following. a. Install a ...

    Owner's tool kit
    Owner's tool kit Owner's tool kit Engine oil drain attachment The owner's tool kit is located under the rider seat. The service information included in this manual and the tools provided in the owner's tool kit are intended to assist you in the performance of preventive maint ...

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