Intermittent ignition fault

[David Simmons]

Having a problem with my 1962 G2. The ammeter, when switched on, drops to the -ve range. I then attempt to start the bike, it coughs and fires for maybe 6-8 times, then dies and the ammeter is then on 0. I operate the kickstart lever, and after several attempts the ammeter then goes back to negative, and the whole process starts again.
Bike had a 12v negative earth conversion before I got it. This is a new fault, bike ran when purchased.
My question. Where to start looking for intermittent ignition faults, and is this a common one?

[Ralph]

Check the points are clean and opening and closing right gap and not sticking,
it will only show a discharge when the points are clean and closed as the points
open you should see the amps return to the middle

[Red Gauntlet]

Check your headlamp switch plugs, sometimes they become loose and cause problems. Also if it is already 12v put a Boyer ignition kit in it, super easy to fit and you will be amazed at the difference in performance.

[well oiled]

I had an internal fault inside the ammeter, making and breaking contact at random, causing odd starting and running problems. This type of problem can be eliminated as a possibility by connecting both ammeter leads to one post taking the ammeter out of the circuit temporarily.