I went off on the rally and sure enough charging stopped after 10 mins or so. Luckily I did not need my lights during the weekend.
For some reason the regulator coils had got very hot and I assumed that was the cause of the lack of charge and removed it, but all seemed ok and the contacts opened when connected to a battery etc. A curve ball was that the 15amp fuse I'd fitted on the charging output (between regulator and ammeter) had blown but I eventually figured that out.
Once again cleaning the regulator points fixed the charging problem, so I took it apart and found the adjuster/point was different from a spare I had from a "parts" regulator I got with my basket case bike years ago. I am pretty sure the special metal "tip" had fallen off the adjuster/ point in the past
- which is why the points became "burnt" and non conducting so quickly
I've swapped the duff adjuster for the good one and so far all is well
I've attached a pic of the adjuster, and semi fried regulator...