Yamaha YZF-R125 Service Manual: 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.


  • Positive tester probe
    horn terminal "1"
  • Negative tester probe
    horn terminal "2"

Checking the horn


c. Measure the horn resistance.

2. Check:

Horn sound Faulty sound Adjust or replace.


a. Connect a battery (12 V) to the horn.

b. Turn the adjusting screw in direction "a" or "b" until the specified horn sound is obtained.

Checking the horn


    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 ...

    Checking the fuel sender
    1. Drain the fuel from the fuel tank. 2. Check: Fuel sender resistance Out of specification → Replace the fuel sender. a. Connect the pocket tester ( × 10) to the fuel sender c ...

    Other materials:

    Assembling the oil pump
    1. Lubricate: Oil pump inner rotor Oil pump outer rotor Oil pump driven gear (with the recommended lubricant) 2. Install: Oil pump outer rotor Oil pump inner rotor "1" Oil pump driven gear Pin "2" NOTE: When installing the inner rotor, align the pin "2" in the oil pump sh ...

    Checking the starter clutch
    1. Check: Starter clutch rollers "1" Starter clutch spring caps "2" Starter clutch springs "3" Damage/wear Replace the starter clutch assembly. 2. Check: Starter clutch idle gear Starter clutch gear Burrs/chips/roughness/wear Replace the defective part(s). 3. Check: ...

    Checking the rear brake master cylinder
    1. Check: Brake master cylinder Damage/scratches/wear Replace. Brake fluid delivery passages (brake master cylinder body) Obstruction Blow out with compressed air. 2. Check: Brake master cylinder kit Damage/scratches/wear Replace. 3. Check: Brake fluid reservoir Cracks/ ...

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