DIY: How to make a buzzcoil

While restoring my 1925 Wickström marine engine last winter, I came across some problems with the Bosch FF1-magneto that came with the engine. Since I don't have the knowledge to restore magnetos yet, I decided to put it on the shelf waiting for better days.

I decided to build a powerful, reliable, yet simple, buzzcoil. After browsing the internet for schematics without results, I stumbled upon this great plan that I wanted to share. All you need to build it is:

- a 12 volt automotive ignition coil

- a 12 volt 30-40 ampere 5-pin relay. Note: it's got to have an 87 and an 87a- marked pin.

- any automotive ignition capacitor

- some electric wire

- solder, soldering iron or wire connectors

- a hose clamp

Here is the building plan. 

Connect a jump wire from pin 87a to pin 86. 

Connect a wire from pin 86 to the positive terminal on the ignition coil.

Connect one end of the capacitor to the positive terminal on the ignition coil, and the other end to pin number 30.

Connect a wire from pin 30 to the ignition switch, and a wire from the second terminal on the switch to the positive terminal on the battery.

Connect a wire from the negative terminal on the battery to a main power switch, then from the other terminal of the switch to pin number 85.

Connect a wire from pin 85 to the negative terminal on the coil. 

Connect a wire from the negative terminal on the coil to ground.

Next step is to test the buzz coil. Connect a spark plug wire from the coil to the spark plug, and connect the ground from the coil to the ground on the spark plug. Turn on the main power switch and hit the igntion switch.

My buzzcoil produces an almost 2 cm long spark.

Next step is to build some kind of case for the ignition system. I used an old wooden box that used to contain a wine bottle, but one can use any kind of box really.

Beware: this buzzcoil produces some seriously high voltage!