AJS & Matchless Owners Club

With the age of these motors it's reasonable to assume nothing. Check and re-check everything. You have to go back to basics.
I've seen rotors a long way from being central to the stator and they still work. Rotor widths do vary, some have recesses, some not.
It's easy to measure from the joint face of the outer cover to where the centre of the stator is. Then measure same from joint face of the inner to centre of rotor. Add, adjust or fit spacers inboard and outboard of the rotor to get it as near as you like. Make sure the rotor will be clamped before the nut runs out of thread on the shaft OR is likely to damage the breather. This also clamps the inner race of the drive side roller bearing to the crank web.
Throw away any tab washers – they are useless - they always turn and break the tab off. Clean threads on crank and in nut with petrol or brake cleaner and use Loctite. They did not have that in those days. Brilliant stuff for us British owners. I have not used tabs for 30 plus years. Lock engine and tighten nut with socket and 2 foot long strong arm (breaker bar). Or hammer impact wrench.
Measure total length from inner joint face to end of crank nut and determine the outer will fit without the nut boring a neat hole through it. Make sure there is enough clearance between the stator and the primary chain.

I ended up buying the triumph spacers I referred to and the pics show both the spacer and it fitted. The rotor is now centralised and ready for the cover to be fitted. I fitted my rotor with the lucas outwards for a few reasons. The twin timing marks are on this face, the rotor is not handed like the original and the period manuals I have all show the lucas fitted outwards for earlier versions of the rotor. I agree that with changes in parts etc there is no standard way of fitting things like this anymore, the original 6v one I removed would have had the lucas on the inside it it had been fitted correctly as the handing showed.

I now have good charging and the headlamp has a nice halogen in it which is much brighter than before. Now considering converting the sunbeam scooter to 12v from 6v as well!