No spark

Chuck. Try this link; Grant Tiller | Custom Norton Commando Wiring Diagram (Jerry Quihampton)

Scroll 1/2 way down past the Boyer stuff.

Testing the switch using #1 as common each station in turn should give you a reading on your equipment to prove continuity, if not the switch is faulty at these internal contacts. May just need a bit of cleaning with contact cleaner and the motion of turning the unit with the key inserted.

Position 1 - full anti-clockwise - parking lights - 1 connected to 3

Position 2 - clockwise 1 stop from P1 - off, nothing connected

Position 3 - clockwise 1 stop from P2 - ignition on - 1 connected to 2

Position 4 - clockwise 1 stop from P3 - ignition & lights on - 1 connected to 2,3,4

Hence brown/blue (from battery etc.) to 1, white (ignition etc.) to 2, brown/green (side lights) to 3, blue/yellow (headlight) to 4.

It is quite possible for the connections in the switch to be poor and/or intermittent. So it might show good with a multimeter but be unreliable under normal load.

Or the switch is an old 80's Triumph one. If I remember rightly they needed a diode across 2 of the terminals to work correctly on a Norton. 

So it might show good with a multimeter but be unreliable under normal load. One of those situations where you apply 12V and try switching on the 'rear light' as a load. Yes the Triumph switch needed the diode to enable the rear light AND the side to be enabled as parking. This is one situation where faffing with an old switch in a motoring situation could be dangerous.