This exercise is on the bench with a drill. Ignition fully advanced, points 0.012" and a mark white paint where the points are just opening. But no spark. I also use a strobe light.
There is however a spark when the points sligtly retard.
So the engine will start (I have the fantastic Concentric 626) but cannot use the fully advance position.
John
email (option): john.kater@chello.nl
John,
This happens sometimes when the rear of the armature is damaged and the gap is to wide. In that case the contact breaker points base can turn on the armature and it has turned in the wrong direction (i.e. too early) it might not spark because it's not positioned right in the magnetic field. If you retard the ignition it will start to spark. I have had this same problem. You either have to adjust the oints base on the armature or better still fit a better armature which isn't damaged.
regards,
leon
email (option): leonhop3@planet.nl
Thanks Leon, Yesterday I worked on the magneto and after putting it back together (with no leftovers 
)no spark at all. Now I see your answer and you are right. The armature end , points side, is damaged. So I will try to set it in the right position. 
The points however are 0.012"
There are a couple of test on the armature as you know. I get 3,3 Amp and a spark.
John
email (option): john.kater@chello.nl
Hi John...I would keep your eyes open for a good, undamaged armature. The part that is damaged is difficult to repair and currently there are no replica mag armatures...and you may well have to replace it at some point...Ian
email (option): ian@wright52.plus.com
Yes Bruce, that's right. I just finished my research and take this opportunity to warn everybody to be carefull holding the sparkplug when turning the magneto.
I own the bike for 45 years and she still shocks me 
email (option): john.kater@chello.nl
Will do Ian
John
email (option): john.kater@chello.nl