What you say about gearing is interesting. I have a book on Norton Commando Tuning by Paul Dunstall, in which he states that factory geared machines are often overgeared to keep the revs down and that ideally one should gear for maximum engine power at the anticipated (but realistic) road speed. I shall certainly consider a 22 tooth sprocket.
As it is I'm still running-in my engine, having covered some 700 miles, but increasingly opening it up. It has a Drags HS cam and 7.5:1 piston. Interesting to note but at around 3000 rpm the engine personality changes. The exhaust takes on a different sound and it pulls - just have to resist the temptation although I did take her up to 75 mph the other day (well so the speed said).
So, it would seem that 6-65 is considered kind. That is good and I shouldn't be so pessimistic concerning my beloved Ariel!!
Editor Cheval de Fer
1950 Rigid Ariel VH
1951 Rigid Ariel NH (under construction)
1973 Norton 850 Commando Interstate