Kirby Rowbotham (Kirby is his first name, as i failed to realise...) is doing a Pazon system for my Sunbeam S7. (He answered both my calls himself.) This will replace the points and the Lucas ATD (ATD stands for "approximate timing device") in the original dizzie. It'll cost about £240. The bike ticked over like a steam engine, ran OK when the revs came up, but in between, when it was supposed to be gradually advancing the ignition, it didn't. Made riding in traffic a trifle difficult...
The most important part to replace is the ATD. These are OK if new (my Vin now has a new Roy Price item - with a magneto - which has made a huge positive difference) but I have ATD's in the box of bits I got with the Vin, all rusted to hell, and have two Sunbeam ones, which could be dismantled by turning them upside down and shaking. Even if KTB hadn't already told me what to expect, I could have figured that Lucas mechanical ATD's don't last forever. Nor, I personally believe, can they be satisfactorily repaired. (I also have five alloy idlers, all with a tooth missing. Go figure...)
Pazon appears to have improved on Boyer Branston because while BB defaults to full advance when the voltage drops, thus wrecking electric starters, or insteps, Pazon doesn't. This apparently is a big problem with electric start Norton Commandos, on which the voltage drops quickly below the BB threshold when the starter is operated. I ought to say "allegedly", because I'm no expert. But it sounds plausible.
I believe that Francois Grosset designed his own dizzie using a Honda (and therefore functional and reliable) ATD, plus electronics, specifically for this reason. If the ATD does NOT reliably return to full retard, then on the next attempt to start the motor may backfire, wrecking the sprag clutch. Francois's starter uses a sprag clutch.
Tom
What I found was that while the Pazon site described systems for many bikes, they weren't all available as kits in UK. KR however builds "custom systems". But make sure whatever system you buy it replaces the ATD, because that's the Achilles heel of Lucas ststems.