The 145mm stroke figure you quote is incorrect if they are motorcycle crankcases...There is no British bike of any make with a stroke length that long...I think the Model 19S Norton is the longest at 120mm...
The figure you give isn't the conrod length is it?...To correctly determine the stroke measure from the centre of the big end to the center of the cranks mainshaft in mm and then double that figure....The engine number also doesn't match the usual BSA numbering system...
