AJS & Matchless Owners Club

50's Royal Enfield Bullet with SR1 used an auto advance with a steel gear. BSA's was a thick fibre gear. Triumph also had a fibre gear but thinner and available with an alloy gear which may suit but at £230 not worth the risk? I remember a stallholder at Stafford years ago who sold and reconditioned auto advance units and he had some labelled for AMC twins.
Dave.

Beesa gears are 44 T, and Triumph 50 T, diameter 73mm (smaller than ours).
So they won't do unfortunately Dave, regardless of whether the diametral pitch of the gears is right.
Vincent ones also no go (and work 'the other way' for clockwise drive magnetos). Don't know about the Oilfield unit as haven't got one, or a timing gear train to compare sizes. Think we need a specific gear to suit - wonder where the guy at Stafford got 'em from? Then it's 'just' a question of mounting the mechanism centrally on the gear and making sure there's clearance under whatever timing cover is being used. Quite a few variables involved, and also a fair bit or work.
In the pic, Beesa versions various, one with alloy gear, plus some new fibre gears, fat for Bs and skinnier/ recessed for Tri.
The actual ATD mechanisms are very similar in degrees of movement, but there are variations, see the Lucas specs here (where no AMC twin version is listed sadly).
http://www.brightsparkmagnetos.com/libr ... ations.htm

Just an idea : why not install a Thorspark electronic ignition ? This solution will be cheaper than a complete mag refurbishing, and very easy to perform. There is a lot of topics regarding this modification.