What color wires are coming from the motor? There should be black,white and blue wires coming out from the Magneto housing. The blue one goes to your wiring harness the black one is your ground and the white one is for powering lights or whatever.
I suggest adding a second accessory coil that you can buy online for about $30.
This will allow all of the juice generated by the first coil to be dedicated to the motor and the second one you can use to power your lights or what have you.
Motorized Bicycle Lighting. Bicycles and Motorized Bikes.Avoid Accidents.Avoid Tickets.Get Lights! This item is designed to be affixed inside magneto case of 2 cycle engine to provide a self sufficient and dependable lighting system.
www.ebay.com
This ones 40 bucks but you can find them cheaper.
Cut the white wire off and insulate the end of it or just snip it off at the coil. Its useless.