The alternator stator had screwed up. It tests out fine with the multimeter but as soon as the engine gets warm it breaks down. I fitted the stator off my spare engine and all is good again.
I have now read this thread several times for a long time , very interesting !
Thanks for all the information and the nice pictures .
Planning my to work with my R100GS this winter and it will be something similar, hope for the same good results.
Best regards från Alf in the North of Sweden