Mag lock

[Devlin]

HAs anyone ever came up with a way to lock the mag to prevent it turning when settiing points and fitting the AR unit,
Dev

[Billybream]

Using a spare earth brush holder you could replace carbon brush with nylon plug to hold armature shaft, not my idea, but copied and it works a treat

[Angus]

I did much the same used a piece of soft dowel.

[Black Sheep]

For setting timing, I hold the points centre bolt with a 2ba socket on an extension. 

[BSA_54A10]

I lock the engine with a piston stop
Then tap ( note tap not smash ) the pinion with a dead blow hammer / mallet
And it has to be a dead blow so that is either leather faced or lead , nothing else yields a true dead blow
This will lock the tapper and allow the pinion to the tightened with out moving

If you do not have one a chep & easy dead blow lead hammer can be made from a welders hammer
Cut the side out of a baked beans can enough to get the hammer in then heat the can while tossing lead into it .
When it is full up to the cut out allow to cool then cut away the can.