Ideally, you should have both armature and field coil designed to deliver 12v. The problem with trying to use the standard equipment and a 12v regulator is that the dynamo doesn't start to produce enough voltage (14v.) until about 2000 r.p.m. which is no good if you're doing slow speeds with lights on. If you're tinking of going to 12v. just so you can fit electronic ignition think carefully about the total cost involved and the fact that you will need total confidence in the reliability of your charging system, and a good battery at all times, to keep the ignition system running. I confess I have a business interest in magnetos and dynamos and my preference is to stick with the magneto as I can kickstart the bike regardless of battery condition.