Finally was ready to ride after new EBC brake pads arrived today and I mounted a 100/90-18 on the front, the pic shows the 110/90 which was too chunky, and it's now on the '73 CB750. I also put some spacers in the forks and they help with the mushiness, but will probably get some new springs soon. Anyway, it was not to be, I am having some electrical issues, I think a bad ground. I'll sort it out though, hopefully tomorrow. I recall the big GS handled a lot better than the '82 KZ1000 I got new - I traded rides with my Air Force pal and loved the GS, way better than the KZ which was no slouch, but power and handling much better on the GS.
Looks like a great bike mate, and with that much RWBHP will scare lots of modern superbikes too, in a straight line, at least.