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 front fork legs
    The following procedure applies to both of the front fork legs. 1. Check: Inner tube Outer tube Bends/damage/scratches Replace. WARNINGDo not attempt to straighten a bent inner tube as this may dangerously weaken it. 2. Measure: Spring free length "a" Out of sp ...

    Assembling the water pump
    1. Install: Water pump seal "1" (into the water pump housing "2") CAUTION:Never lubricate the water pump seal surface with oil or grease. NOTE: Install the water pump seal with the special tools. Install the water pump seal with the special tools to the specifi ...

    Disassembling the water pump
    1. Remove: Water pump seal "1" NOTE: Remove the water pump seal from the inside of the water pump housing "2". 2. Remove: Bearing "1" NOTE: Remove the bearing from the outside of the water pump housing "2". ...

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