Ignition Timing on 1929 BSA S29 Sloper OHV 500cc 4.93HP

[Swoopster]

Hi folks,
Can anyone supply the Ignition Timing for my 1929 BSA S29 Sloper OHV 500cc 4.93HP? I'm particularly interested if anyone has it in degrees BTDC - although i guess the old "pencil jobby down the plughole" method info will help!
Any help/info would me much appreciated.
Cheers
Swoopster

[Dean Southall]

Set piston at TDC.
Set Advance/Retard lever to fully retarded position.
Rotate contact breaker clockwise (veiwed from contact breaker end) until points have opened no more than 3 thou.

They did things differently then!