Each of the straps that hold the magdynamo unit to the crank case are fitted over one of the two studs that hold the crank case together...
The straps can only be removed when the crank cases are separated under normal circumstances...
Removal of the studs from the crank case so that the straps can be removed without splitting the crankcases will generally damage the studs and is not always successful...It is best to weld a nut to the stud if you attempt it...
However, the studs can be replaced with bolts of the correct length if you can get the studs out...Ian
email (option): ian@wright52.plus.com
However, the studs can be replaced with bolts of the correct length if you can get the studs out...Ian
Yes it can but with a bolt it is much easier to strip the threads in the crankcase. especiallly when they are a little short, and that gives a lot more trouble. A stud is placed ones and will not wear out the threads in the aluminium.
This must be reason why BSA used studs instead of bolts, so I would say put them back in.
And don't forgot the straps when the cases are split!!
I agree with that...
I helicoil the threads when I fit bolts but normally I don't make this modification...I've done it on a couple of engines that had competition mags fitted and were going to have a magdynamo fitted later...
That way the straps could be changed without rebuilding the engine...
Without helicoiling the threads I only suggest the bolts as a 'get you out of trouble' solution if there was a problem with a mag strap on a good engine that didn't need stripping..
Plainly some care should be taken regarding using the correct length bolts and not over tightening them in that case...
As a matter of interest, when rebuilding BSA engines I always fit helicoils to the threads in the crank case that the primary chaincases bolt to...Ian 
email (option): ian@wright52.plus.com
Thanks for the addition Ian, I know you are not taking things lightly.
I remembered reading somewhere else a recommendation to simply change the studs for bolts and now we are on the subject thought posting some disadvantages of this method would be justified.
Keep sharing your knowlegde, it is great!
Thanks Michiel...Likewise I'm always interested to hear your point of view as I know you think these things through and on a number of occasions you have come up with something I haven't thought of....Ian
email (option): ian@wright52.plus.com