Many thanks for coming back on that so fast, Hippo.
I found the standard forks underdamped as well as undersprung. In particualr I would get problems with chattering on freeways and unsteady behaviour on rippling country bends.
Upping the oil to the SE HD has helped a lot but may have left the forks slightly overdamped, though things seem to have settled down a bit in the last few days, helped by upping the rear preload a little.
I still haven't managed to confirm my suspicions that I've just moved from 10 to 15 W.
Almost certain you have. I always liked running 15W and with about 1 or 1.5 OZ above the recommended volume to increase preload. No air.
Then you just have to find the tire pressure where the spring rates of the tire and fork are well matched. For my weight and Dunlops it turned out to be 38 psi. The bike liked to run there.
Thanks. I'll take a look. It's shame it's so difficult to get Bel Ray oil here. I used it in my Triumph Bonnevile (old style) and they got on really well - engine, trannies and forks - not to mention the chain.