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:

    Installing the swingarm
    1. Lubricate: Bearings Spacers Dust covers Pivot shaft 2. Install: Bearings "1" 2. Swingarm A. Left side B. Right side 3. Install: Swingarm adjusting collar "1" Swingarm "2" Pivot shaft Pivot shaft nut "3" a. Install, and then fully turn in the swingarm adju ...

    Removing the primary drive gear and balancer gears
    1. Loosen: Primary drive gear nut "1" NOTE: Place the aluminum plate "a" between the balancer drive gear "2" and the balancer driven gear "3", and then loosen the primary drive gear nut. 2. Straighten the lock washer tab. 3. Loosen: Balancer driven gear nut "1" NOTE: Place ...

    Checking the front brake master cylinder
    1. Check: Brake master cylinder Damage/scratches/wear Replace. Brake fluid delivery passages (brake master cylinder body) Obstruction Blow out with compressed air. 2. Check: Brake master cylinder reservoir Cracks/damage Replace the brake master cylinder. Brake maste ...

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