Speedo cable is new, since the bike didn't come with one. And it does oscillate a little, but not much, about what I'd expect for this age. My CB350 is really wild, at speed it can swing around to quite the extreme! But tbh I'm not overly concerned about the speedo, just knowing its off and by how much is good enough for me for now.
Interestingly, cyl 4 compression is fine, at 150psi. But cyl 1 is a bit lower, at 130psi, yet that plug is in line with 2 and 3. I'll be testing compression on them all again once ive got more miles on it.
I'll probably end up with the carbs off again just to absolutely make sure the idle circuit is totally clear, floats are definitely correct etc