Some times the lights will be a bit dimmer at idle, the charging system barely makes enough to run the bike at idle. Once you rev it up a bit, 2000 to 2500 rpm, the charging system starts to make enough to run the bike and charge the battery. When this happens the lights get brighter.
If you hook a volt meter to your bike battery and watch the reading at idle and it will often be only 12 to 12.5 volts. When you slowly rev the bike you will see the voltage rise to 14.5 volts.
if it goes over 14.5 volts by much then you have problems. Too high and the battery boils, bulbs blow and electronic ignition can burn.
I, as well as many others have a volt meter permanently mounted on the bike. This way we can watch the voltage. If the reading starts to read lower than usual we know right away to head home and see whats wrong.
I swapped some parts around on my 75. As I was riding, I noticed that the volt meter was reading closer to 13 volts than 14.5, the usual reading. I went home and started checking things out and found that the rotor that checked out good, 5 ohms at room temperature, would change when hot, 8.5 ohms. The increase in resistance cut back the current through the rotor, this caused the magnetic field to decrease, this weaker magnetic field couldn't get the stator to put out as it should.
With out the volt meter I wouldn't have noticed anything wrong until the battery went dead.
I like my volt meter, I don't like pushing a bike home.
