You say it was a 12 volt and is now a 6 volt. I am assuming you installed a 6 volt coil. The first thing I would try is running a jumper wire from the starter to the coil to bypass all the wiring and the switch. I suppose you do know where the on position is on your ignition switch. If it doesn't do anything with a jumper, pull the distributor cap off and take a look. Its not uncommon for points to corrode over when they set for extended periods of time. Try filing them, but make sure you have no oil on your file.
