A twin output 6 volt coil (12 volts is better still) has worked on my bike for the past 13 years. It was supplied by Boyer Bransden who also made the ignition control device which controls advance and retard. A good charging system and battery are required of course but dynamos seem to be reliable when used with one of those solid state regulators. The spark triggering is controlled by a simple device mounted inside the modified magneto. Ignition timing is easy to set and a strobe lamp can be used if you’ve got one.
I can send a few photos of the installation if you wish via E-mail.
There is more to this subject than is immediately apparent, but the benefits are reliable accurately timed sparks.
Hope this is helpful but get in touch if you need to know more.
John
