An update on my ignition problem for anyone with similar issues:

It turns out I'm not as clever as I thought : After leaving the bike for a few weeks it had no spark again. I got it running once again by turning it over with a cordless drill as before (plug out) whilst switching the kill switch, (or ignition switch) on and off until it sparked. As all coils measured OK and had a voltage output when checked, I guessed it must be the CDI unit. Changed it with THIS and it all works fine.

Good find Nick, well done matey.

Rex's had sort of appeared on the edges of my radar from time to time, but I had it in the back of my mind that their replacement cdi came with 12v conversion and cost north of £300. That price seems much more reasonable - and no postage and import duties either!!

Regards.

Alan

Thanks Alan.

Yes, I couldn't justify the full conversion and this system seemed a decent alternative. However it's a bit fiddly to fit because the lighting coils have to be swapped, but not beyond the abilities of most. The only negative is that it's not possible to adjust the ignition timing. That said, it seems to work very well.