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Starting problem after magneto rebuild

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Thank you everyone you have given me some great pearl of your wisdom. I will try them out and let you know the results.

A further comment from another forum:

"Tight wire advance was the norm till around the 50's on BSA's.
M's remained that way AFAIK till the end of manual advance where the B's & A's got slack wire advance.

As for timing.
The .003" opening at TDC assumes that the points are .012" at full lift,and both sprockets are in the correct positions on the engine & magneto , if it is differnt then the timing will be out.
Now the easiest way to alter the timing is to change the max points opening, try it at .002" increments
IF you think the spark is too far advanced, close down the points gap a thou or two.
You can knock around .004" to .006" off the max opening and still get a spark, although it might break down at higher speeds so this is only done to quickly test the timing and not for running.
If the engine starts then the sprocket has slipped on the magneto.
If the magneto has just been overhauled then it should produce sufficient energy to spark at less than optimal flux opisition although it might brak down at higher revs.
From ( unreliable ) memory the magneto sprocket is on a plain taper and the engine sprocket is keyed.
Thus it is very easy to get the sprocket in the wrong position.

The opposite occurs when you enlargen the max opening so you can go each way very quickly to test if you have the timing right."


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