Ballast Resistor for Coils originally fitted to Laverda, Ducati and other models 

This electrical resistor is switched in and out of the supply voltage to the ignition coil. The ballast resistor lowers the voltage after the engine is started to reduce wear on ignition components and allows the coils to run cooler. It also makes the engine much easier to start by effectively doubling the voltage provided to the ignition coil when the engine is being cranked.