I had the same experience a while ago. To remove the forward nut is easy, the installation is a nightmare. However I changed the position of the 2ea guiding pins to the front and fixed the magneto with the 2 bolts in the rear. The installation of both bolts in the rear position is quite easy and operational wise I had no problem so far. Neither the magneto came loose nor the chain slackened during the last several 100 miles.

Many thanks for replies.

I made two thin ring spanners to fit magneto fixing nuts and used tape to secure nut inside ring spanner.
Worked a treat.

Regards Ian

I've found that there are usually 2 locating pins and 2 bolts that go into the mag from underneath and they can be a right pain.
Usually one bolt is on the rear right, not too difficult to do and the other is front left with the pins in the opposite diagonals. You can often get a long thin bar of metal with a blob of grease on it to help with the right rear. A flat strip of metal ,or whatever you have, to hold the front left bolt in place while using a cranked spanner to slowly tighten it. A good time to practice your Anglo Saxon expletives. Of course when they were new the mag was on the engine when it was installed in the bike,,,  doddle.
John hood

Hi Ian, what do you mean with XXXX nuts? There are only regular nuts. Maybe a picture?
Cheers, Thomas

Hi
For the experienced
Is there a technique, special way to get those XXXX nuts on the magneto platform threaded studs.

Regards Ian