Firstly apologies this isnt a Scott query but tech help on my rep is plentiful – The ‘beam is far scarcer and the owners club next to non existent.
Does anyone know the valve timing on a 1937 Series 2 Sunbeam model 9? All the literature I have explains the use of timing marks only. Unfortunately my pinion has no marks so it needs to be done the proper way with a timing disc. – Please note this is a 37 Series 2 which has much hotter cams than the earlier bikes.
I do not have an exact answer for you, I am neither familiar with the model or how the valve gear is laid out but there is usually a sort of symmetry involved with 4-stroke valve timings.
In general valve events between makes do not vary all that much despite what the adherents to any particular marque would have you believe. When it comes down to it all 4-strokes go suck–squeeze–bang–fiss!
Wild valve timings will provide more power at the expense of tractability but really it is the whole valve train, subtle cam and follower profiles and good port design that make the real difference.
That said I would expect the timing for a road machine to be something like the following:
Your machine will obviously not be exactly the same but this is a good starting point. If the above fairly representative angles are expressed as a percentage of the stroke, (180°), as indicated above then if you measure when the cams on your machine open and close it should be possible to apply these percentages to your timings. If still in doubt set the inlet opens and exhaust closes timings disposed about TDC as above and then check inlet closes and exhaust opens and see how they compare.
Do make a neat diagram to refer to and remember that these confounded 4-strokes do 720° to go round once — begorrah!