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:

    Assembling the crankcase
    1. Thoroughly clean all the gasket mating surfaces and crankcase mating surfaces. 2. Apply: Sealant (onto the crankcase mating surfaces) NOTE: Do not allow any sealant to come into contact with the oil gallery. 3. Install: Right crankcase NOTE: Turn the shift drum segment ...

    Setting the normal mode
    NOTE: The engine speed, coolant temperature, and fault code, if detected, can be displayed on the LCD of the FI diagnostic tool when the tool is connected to the vehicle and is set to the normal mode. 1. Set the main switch to "OFF" and the engine stop switch to "". 2. Disconnect the self- ...

    Checking the rear brake caliper
    1. Check: Brake caliper piston "1" Rust/scratches/wear Replace the brake caliper piston. Brake caliper cylinder "2" Scratches/wear Replace the brake caliper assembly. Brake caliper body "3" Cracks/damage   Replace the brake caliper assembly. Brake fluid deli ...

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