Thanks Julian, I didn't know that about the RGS.
I guess the old way of looking at overall ratios is the least confusing when discussing gear ratios.
By my figuring, a 23 tooth engine with 46 tooth rear is identical to a 21 tooth engine and 42 tooth rear.
When you say the RGS had a lower geared gearbox, I assume you are referring to the first three gears only as top is 1 to 1?
Again, that is surprising, I would have guessed that the RGS had intermediate ratios more along the lines of the Goldstar close ratio type with very high first rather than ratios you might find on a sidecar tug.
The many and varied ratios of the BSA gearbox is a topic that I have barely scratched the surface of, not sure I'll ever dig into that one!
STB box on this late 63 SR.
Glen