B31 ignition points worry

[DGBland]

When I try and set up the ignition timing with a light and battery, the light stays illuminated with the points open or closed. I have set the timing the old fashioned way with a bit of paper but I am worried it won't spark if there is a current running through the points open or closed. When I took the magneto off it worked fine and started every time. Has anyone one else had this problem and is it just a case of dismantling the points and giving it all a good clean?
One step forward and three steps back with this bike

Thanks
David

[neil1964]

 A basic lamp will not work as you will always have continuity through the magneto coils.
You need a set up that either measures a change in resistance (commercially produced buzz box) or an inductance meter which will detect when points open.
Fag paper is tried and tested method for B31!!

[DGBland]

Brilliant thanks. I thought I had broken it again. It's set up with the fag paper method now

[Pete C]

 I have used a "buzz box" for years now and it makes the processs much easier and the hand you use to pull the fag paper if now free (you need to pull the fag paper on one side of the bike while tightening the mag pinion on the other side).
They cost about 30 quid so may not be worth it if you are only doing the job once.
There is one with ebay number 194223708176, not the one I have but very similar.

[DGBland]

Thanks I might look for one of them because you never know when you might need one. Sounds like a good investment