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 charging the battery
    WARNINGBatteries generate explosive hydrogen gas and contain electrolyte which is made of poisonous and highly caustic sulfuric acid. Therefore, always follow these preventive measures: Wear protective eye gear when handling or working near batteries. Charge batt ...

    Replacing the rear brake pads
    NOTE: When replacing the brake pads, it is not necessary to disconnect the brake hose or disassemble the brake caliper. 1. Remove: Brake pads Brake pad spring NOTE: To remove the inner brake pad "1", push down on the brake caliper bracket so that there is space to remove the brake pa ...

    Removing the handlebars
    1. Stand the vehicle on a level surface. WARNINGSecurely support the vehicle so that there is no danger of it falling over. 2. Remove: Handlebar grip "1" NOTE: Blow compressed air between the handlebar and the handlebar grip, and gradually push the grip off the handleb ...

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