Can't see from pix on their web site whether the Joe Hunt thing has the same tapered shaft for the pinion or ATD as a Lucas. Can't see any shaft at all in fact in their pictures. Assuming it does, which it ought to as they are claimed to be a direct replacement in pre-unit applications, then you need the standard ATD unit unless there is any option for manual operation. Suspect there isn't, as weren't these things developed originally for industrial engines, which would normally run at pretty constant revs?
Getting an ATD looks easier said than done. Not sure where you are, but Draganfly in the UK do an exchange-only rebuild service (only of use if you can find a dead one somewhere). I thought SRM sold them complete but can't see them on their site as a complete unit, just various of the bits. But worth a call or e-mail to them I'd say. Haven't looked on e-bay because I hate the place, you probably have.
Maybe someone else here knows who's got 'em available without the need for an old one to exchange?
Doesn't sound as if 'original' is critical to you, so an alternative would be to find a Lucas manual mag and get it sorted (it will work for longer than many of us are going to live). Could probably get one and sort it out for the value of the thing you've got, looking at what they cost. Look a lot better on the bike, too.
