Here's a circuit which has worked for me. It's basically the "vibrator" circuit that stevez described. It uses a pushbutton switch and a double-pole, double-throw relay. Here's how it works: When you push the switch, the current flows thru one set of the relays normally closed contacts. This causes the relay to energize, pulling in the contacts. When this happens, the relay breaks it's own power and releases. This happens very quickly and will continue as long as you hold the switch. The relay will make a buzzing (vibrating) sound, the speed of which is limited by the mechanical parts of the relay. The second set of contacts (used to control the ignition coil) are simply along for the ride... they make and break at the frequency of the buzz. Also, like stevez said, these relay contacts will likely burn out eventually. This method can generate some pretty hot sparks between the contacts of the spark gap. Be careful ... it can pack a punch! JB