Yamaha YZF-R125 Service Manual: Checking the rectifier/regulator

1. Check:

Rectifier/regulator output voltage Out of specification → Replace the rectifier/ regulator.


a. Set the engine tachometer to the spark plug lead.

b. Connect the pocket tester (DC 20 V) to the rectifier/regulator coupler as shown.


  • Positive tester probe
    red "1"
  • Negative tester probe
    black "2"

Checking the rectifier/regulator


c. Start the engine and let it run at approximately 5000 r/min.

d. Measure the charging voltage.

    Checking the stator coil
    1. Disconnect: Stator coil coupler (from the wire harness) 2. Check: Stator coil resistance Out of specification → Replace the crankshaft position sensor/stator assembly. a. Conne ...

    Checking the horn
    1. Check: Horn resistance Out of specification Replace. a. Disconnect the horn connectors from the horn terminals. b. Connect the pocket tester ( × 1) to the horn terminals. Positiv ...

    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 ...

    Disassembling the front wheel
    1. Remove: Oil seal Wheel bearings a. Clean the surface of the front wheel hub. b. Remove the oil seal "1" with a flat-head screwdriver. NOTE: To prevent damaging the wheel, place a rag "2" between the screwdriver and the wheel surface. c. Remove the wheel bearings "3" with a ge ...

    Checking the swingarm
    1. Check: Swingarm Bends/cracks/damage   Replace. 2. Check: Pivot shaft Roll the pivot shaft on a flat surface. Bends Replace. WARNINGDo not attempt to straighten a bent pivot shaft. 3. Wash: Pivot shaft Washer Swingarm adjusting collar Du ...

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