carb, mag or other fault ?

[Signboy]

Ok guys.... 53 a7 plunger broke down last weekend !, thinking it was a carb problem,got it home and stripped the pre mono block down, cleaned the petrol tap filters , new plugs in , cleaned the points.... bike started back up on first kick !! then, as the revs increase, it starts to back fire and cuts out ! , could it be the mag ?    any ideas,
cheers signboy

[beezermacc]

Do you know anybody with a spare mag?....... Easiest thing to do is fit a spare and see if that fixes it.

[BSA_54A10]

Another job for a color tune.
Failing that get yourself an inline spark tester.
If it flashes while the engie is dieing then it is a fuel related problem.
Light goes out then a spark problem.
Do that get back & we will keep you in the shed for week.

[morris]

Had a similar issue on the SA once. Could sometimes get it running for a short period but then it died. When checking the plugs I forgot to put the righthand plug cap back on and it started first kick on one cylinder. As soon as I put the cap back on it died again. No way to get it started on both cylinders, but pulling the cap off again, first kick. Maybe worth a try?
I think back then the slipring was the cause, but in the end I decided to take the mag off, converted to a Pazon ignition and never looked back so I'm not really sure of my diagnose.