Golden boy / Uncle D - I recently rebuilt my GF (new d/side bearing, turned crank and new t/side bush to fit, rebore, new cam + followers, new valves, springs, guides & seats etc) and am still running it in, but concur that 50 / 55mph is where vibration starts. Not monumental, but unpleasant enough that I wouldn't countenace a long journey above that speed. Revving it higher (as high as I dare, mindful of the old alloy rods) didn't get past the vibration period. Like yourselves, I do not intend stripping the motor again just to balance the crank though, if I did, I'd make it adjustable so that in future the balance factor can be altered without an engine strip - a trick I learned when building one-off engines where the balance can only be a guess to start with. I believe Musky has altered his factor for racing. Apparently that gives bad vibes low down, but presumably is smoother higher up where it will spend most of its time (did the same with my Weslake). Presumably a compromise (with slightly rougher tickover) would better fit the bill. But then I'm happy to poodle along enjoying the bike. It only gets annoying when you want to sample the power and give it a bit of a blast.
