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 front brake master cylinder
    1. Install: Brake master cylinder "1" Brake master cylinder holder "2" NOTE: Install the brake master cylinder holder with the arrow mark "a" pointing forward. Align the end of the brake master cylinder holder with the punch mark "b" on the handlebar. First, tighten the front bo ...

    Installing the throttle body
    1. Install: Throttle body joint clamps NOTE: Align the projections "a" on the throttle body joint with the slot "b" in each throttle body joint clamp. 2. Install: Throttle body joint NOTE: Align the projection "a" on the throttle body joint with the slot "b" in the intake mani ...

    General tightening torque specifications
    This chart specifies tightening torques for standard fasteners with a standard ISO thread pitch. Tightening torque specifications for special components or assemblies are provided for each chapter of this manual. To avoid warpage, tighten multi-fastener assemblies in a crisscross pattern and ...

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