I think I might be being a bit over dramatic with the thread heading, but the speedo needle on my bike does flap about usually in the 40 - 80 mph region by about + or - 5 mph. I've had a look at the drive cable innards and they don't look excessively worn, but I suppose there could be some wear on the end of the cable where it fits into the socket on the front wheel.
I'm not overly concerned with the issue, could it be wear and tear inside the instrument head itself? I suppose after 40 odd years there will be some. I was wondering if there was a quick fix or would it a need an overhaul of the speedo head itself? Prior to owning this 550, I haven't had a SOHC Honda 4 for about 30 years and I seem to remember the ones I had back then did the same, so am I just fussing about nothing?