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igntion bsa

I have an m20 with a ( obviously non-original)thorspark-type ignition. It is mounted in the now empty orinal magneto housing. Advance/retard is manually. For this purpose the original groundplate of the magneto ignition and the advance/retard cable are retained. Cable enters the housing from the right.Ignition shaft spins clockwise. Timing is done in a similar manner as with the magneto :find TDC,turn back 11,1mm,set cable to full advance, set ignition to fire at this point. Bike runs absolutely fine,does not get exceedingly hot , but is something of a bugger to start.To help trying to improve this :can anybody tell me how many mm from TDC the ignition should fire when retarded,so on
start-up ?
Many thanks in advance and I will let the result be known.
Maxim Jurgens
Phuket, Thailand

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Re: igntion bsa

I retard my M20 ignition by about half for starting. Anything over that and it kicks back. So I guess the piston position would be around 5-6mm BTDC. Ron

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