Well I rewound the low rpm coil (3000 turns) of 0.14 diameter wire. The guys at the local winding shop lent me the complete reel of wire as they couldn't be bothered to run of 200 metres for me.
In the meantime I removed the head, and replaced the head gasket with a more recent one, but nothing untoward under the head - all OK.
Finally I replace the old stator with my rewound race stator (see pic) and low and behold it works fine. so I had troubleshot to the right component after all. All that bugggering about with the carbs and head etc... and it was the good old stator the whole time!
Anyway, my good friend Borut from Zeeltronic, has another technical trick up his sleeve. He produces a box that will convert the battery current to a sufficient level to feed the Capacitors, giving a flat steady current to the CDI, which he convinced me would be better than changing stators every other race, so I let myself be convinced, and I have one on order - I am really excited about this, because although it means I have to keep the battery it means I can use a significantly lightened flywheel and race stator (even without the CDI charging coils), and I will have great sparks!