Hi Steven,
In my '50 Norton (model 7 Dominator) I use Miller's Millerol SAE 40 or 50 in as well as engine as gearbox. For me SAE 50 works fine, but then again I don't drive below say 5 degrees Celsius. Engine has sufficiently pressure (oilpump new in 2007, though) and gearchanges go smoothly.
For the oilbath I use Milleroil SAE30; clutch works fine (no slippery) and leakage form the oilbath are well within my standards.
I'm sure that e.g. Castrol has equivalent oils. Be aware for detergents (in the Netherlands we call it "doped oils") for they might loosen up sludge from the crank and bearings and there's no filter within, is there?
No multigrade adviced, because the molecular strings appear to get broken and the result is a far to low viscose oil. (Becomes too thin)
Are these tips any good to you?
Kind regards, Rien
Netherlands.
If you've got a single cylinder Norton (ES2, 18, etc),