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:

    Removing the lower bracket
    1. Stand the vehicle on a level surface. WARNINGSecurely support the vehicle so that there is no danger of it falling over. 2. Remove: Upper ring nut Rubber washer Lower ring nut "1" Lower bracket NOTE: Remove the lower ring nut with the steering nut wrench "2". ...

    Checking the drive sprocket
    1. Check: Drive sprocket More than 1/4 tooth "a" wear Replace the drive chain sprockets as a set. Bent teeth Replace the drive chain sprockets as a set. b. Correct 1. Drive chain roller 2. Drive chain sprocket Checking the rear wheel sprocket Refer to "CHECKING AND R ...

    Installing the rear brake caliper
    1. Install: Brake caliper "1" Copper washers Brake hose "2" Union bolt "3" WARNINGProper brake hose routing is essential to insure safe vehicle operation. Refer to "CABLE ROUTING" on page 2-33. CAUTION:When installing the brake hose onto the brake calip ...

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