Mag bolt removal
Just a thought, Is it right hand or left hand thread.
In your atempt to remove the nut you may be tightening it, let me explain,
You need to ascertain in which direction the Mag/ motor is turning when running, to do this either put it in gear and turn the rear wheel or just touch the starter button.
If the Mag/motor runs clock wise you have a left hand thread,
If the Mag/motor runs anti clock wise you have right hand thread,
Its done this way so that the nut does not come undone.
It may also help if you use some heat on the nut as it my have threadlock on it.
Hope this helps