A motorcycle horn produces a weak, raspy buzz instead of a clear, loud tone. What is the standard adjustment procedure to correct this?

1. Turn the small adjusting screw on the back of the horn in or out until the diaphragm vibrates at its correct resonance, producing a clear tone.
2. Increase the system fuse rating to force more current into the horn solenoid.
3. Pour a small amount of lubricating oil into the horn trumpet to soften the diaphragm.
4. Bend the metal mounting bracket to change the horn's angle relative to the engine.