Ignition timing

Hi all -
I am setting my ignition timing statically on the bench for now . 750 Combat with points and Lucas centrifugal auto advance. Specs call for 28 degrees BTDC fully advanced. The back of the auto advance is stamped 12 degrees.
Do I dare set timing to 16 degrees BTDC with the auto advance in the retarded position so as to avoid the hassle of holding the bob weights open ?
I have made up a washer that clears the points followers and shaft of auto advance unit to hold weights open but it is a PITA to have to remove the bolt and reassemble with correct washers .
Thanks for any input- RT

No, the 12 degrees is at the cam not the crank, its 24 degrees at the crank, so initially you can set to 4 degrees fully retarded. But this does not remove the need to strobe as early as possible in order to stop the risk of holed pistons. A simple stepped washer will allow you to lock the AAU fully advanced and then you can set to 28 BTDC, strobing is still needed.

The 12 degrees advance range will not be accurate.

Thanks Gents - as I feared . Any way I believe I have a leg up on it now . Left cylinder points hooked up to continuity buzzer on my multimeter with stepped washer holding weights open - buzzer stops at 28 degrees BTDC . Removed bolt and reassembled with weights in @ full retard position. I’ll now check at what point in degrees they open . In a perfect world timing disk should read 4 degrees , correct ?

To be honest as TT confirms the retarded figure will not be accurate and is best ignored, BSA gave retarded timing figures in the early 60's but stopped when it became clear the fully advanced is the key measure. Only worth checking if the bike is difficult to start as its firing point is too retarded, ie if someone has opened out the AAU timing window to 15 or 18 degrees to stop kicking back.

Richard Tool said:

Left cylinder points hooked up to continuity buzzer on my multimeter with stepped washer holding weights open - buzzer stops at 28 degrees BTDC . Removed bolt and reassembled with weights in @ full retard position.

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Did you set right hand cylinder points before removing the locking washer(s)?

L.A.B. said:

Did you set right hand cylinder points before removing the locking washer(s)?

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Yes , both cylinders now showing loss of continuity across points at 28 degrees BTDC on their respective compression strokes with auto advance locked in advanced position. However in my excitement I have neglected establishing proper gap so back at it again .
Thanks all for the helpful responses .
Cheers ,- RT

If you intend to strobe it then there's no need to spend a lot of time trying to get the static settings spot-on just use the strobe to set the timing.