Having the mag on the bench makes it easy to check the rotation.
Anti-clockwise from the drive end is what you want on the bike.
Before doing anything else, you can stick a plug on the HT lead and holding the plug against the body to earth it, turn the mag smartly anticlokwise, and see if you get a spark. A good one will easily make a 1/4 inch spark with a smart flick, probably with the drive sprocket on to give you some leverage. But it could be that the points are filthy, the condenser is dead or something, so you need to look further . . .
If you take the plastic cover off, and then rotate the mag anti-clockwise by hand, you should see the points start to open
just after - a few degrees only - a 'flip point' of the mag. (There are 2 per rotation.) The cam is set on a taper only, no key. So can be extracted and moved to the correct position if need be. The Lucas instructions here explain all and more you could want to know:
http://www.brightsparkmagnetos.com/libr ... %20SR4.pdf
For cam timing see Fig 9 on page 8.
Chances are, if the thing came off a motorcycle, it is set for anti-clockwise, as it's far more common than clockwise.
The nut on the side is not a Lucas bit as alanengineer says, nor I think is the insulator below it, which is askew. But as long as the screw and nut are insulated from earth, no problem.
That's where you could run a stop button from, which I mentioned in another post. It's also the place where a bendy tag is fitted on many mags, which you push till it touches the body, thus earthing out the low tension live side of the instrument. Far better on a bike, I think, to have a remote stop button, using a horn push or similar, on the 'bars. Then you can stop it quick if you have to, without having to operate the decompressor assuming there is one.
