Norton Atlas Automatic Advance Unit 47508

Does anybody know how you remove and replace the center bolt from the Atlas automatic advance unit? My dished washer ( with the two small holes ) needs replacement. Thanks

The center bolt has two sets of threads. One right handed to attach the AAU to the Magneto input shaft and a set of LEFT HANDED threads to allow for the bolt to be unscrewed from the AAU, (please see photo below):

If you cannot unscrew the bolt from the AAU, it probably means the left handed threads have been abused. Then it becomes a bit more interesting!