6 volt systems don't need a ballast resistor, internal or external. The same procedures apply to positive ground- - - -you need to see battery voltage at the "upstream" coil post anytime the ignition switch is on. The downstream (distributor) terminal of the coil will have either full battery voltage or almost zero, depending on whether the points are open or closed. Dirty points are the most common cause of no spark, by far. Just because they're gapped right doesn't necessarily mean they can flow current. One very good way to clean points is with a pencil eraser, but you'll need to take them out of the distributor to do a good job of it. There's just enough abrasive in an eraser to do a very good job of burnishing points without doing any damage to the contact surface. One of the hard white erasers typists used to use was the best of all, but those things are very scarce these days!
Jerry
