How to Wire a Lighting Coil on a Bike

How to Wire a Lighting Coil on a Bike

A lighting coil is used to run a headlight and tail light. It's a long copper wire wrapped around an iron core that creates electricity from the variation of magnetic field through it when the flywheel rotates. The electricity passes through the coil, out its end and back to the bike's ground terminal, which closes the circuit.

If the wiring isn't done properly it can cause damage and a lot of headaches. The best way is to replace the stock stator with a one that has a lighting winding built in. That way the lighting coil will be independent of the ignition coil and won't rob energy from that coil when it is not running the lights.

Another option is to add a second thinner lighting coil piggy backed on the existing coil. That is much cheaper and should provide a good output for your lights. Just remember that it is a balance of voltage output and current - if the coil is too thin it will produce more voltage but not enough current, or too thick it will generate heat which reduces current output.

To do this properly the wire from the lighting coil that goes to ground MUST BE REMOVED AND SOLDERED TO A INSULATED WIRE THAT WILL GO TO THE RECTIFIER ac input along with the other coil wire. If you don't do this it can cause the rectifier to burn up and the coil will not be able to output enough voltage to run the lights properly. The ac output from the coil should also be filtered with a 100uF cap on the dc output to prevent interference with the ignition coil circuit (as well as other systems on the bike).

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