Using Heiko’s instructions in his F regulator special I built a test setup:

photo to follow…

Result on my regulator, it needs some work…

 

Tested an electronic one too, but not sure whether this test setup is suitable for an electronic version…

I did a lot of tweaking of the F regulator and finally got it two respond like I want it to:

 

I hooked the working F regulator up to the Bella. Regulating fine in idle. Then increased the revs and: a spark / flash at the regulator, fuse failed and when I checked the points of the regulator the flat spring was welded to the point.

Finally this gave me the clue to figure out what was wrong with Bella; clearly when the high voltage switch kicks in something shorts. When the regulator goes above 14.4V the switch SR-minus / SR-F switches to SR-F and SR-61. Normally this means collapse of the field, but in my case something shorts. Combine that with the burnt out coils and the only option would be that I interchanged the earth and minus on the regulator. I checked the cabling fully before, but must have made a mistake as sure enough, these two cables were interchanged.

A bit of re-wiring later and the Bella runs like she should. I don’t like the top switching current of the regulator at 15.5 volt rather than 14.4, but I’ll take it!

Next is building the Bella back up and test her on the road. Chore for next weekend…