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 the clutch springs
    The following procedure applies to all of the clutch springs. 1. Check: Clutch spring Damage Replace the clutch springs as a set. 2. Measure: Clutch spring free length "a" Out of specification Replace the clutch springs as a set. ...

    Disassembling the front fork legs
    The following procedure applies to both of the front fork legs. 1. Remove: Rubber cap Clip "1" Front fork cap "2" (with O-ring) Fork spring NOTE: Push the front fork cap in the direction of the arrow shown in the illustration to remove the clip. 2. Drain: Fork oil NOTE ...

    Engine tightening torques
    Cylinder head tightening sequence: Generator cover tightening sequence: Clutch cover tightening sequence: Crankcase tightening sequence: A. Left crankcase B. Right crankcase ...

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