They had 12 volt systems for years with a ballast resistor. The advantage was that the resistor was bypassed when the starter was cranking allowing better coil operation even though the starter creating a large draw. I wonder if the ballat resistors that are offered are actually for use with a coil designed for a 12 volt system. I am assuming that the coils used with the resistor, from the factory, were different from the 6 volt coils.
