How about a hacksaw or Dremmel cut from the top of the dome nut as far down as you can, then a small screwdriver blade in the saw cut and a bit of levering to split the nut. Ron
Hi no need to get physical take out brushes from opposite end then undo the two through bolts holding dynmo together pull it apart thus exposing the offending bolt end mal
Thought of that but the Dynamo driven gear would need to come off before you can take it apart and that is held on by a screw that is not accessible. At least as far as I can see.
What he was proposing was to leave the gear on the armature and remove everything else from the front plate of the generator leaving the armature dangling in the front bearing.
I just did a 'proof of concept' and that should give you access to the screw-head from above?
This assumes you can wriggle the body of the generator out but with the straps undone that wasn't an issue with the old generator I tried it on?