The tach one my '73 Commando has gone haywire. It's either zero or 6-7,000rpm. It worked fine ten years ago which was the last time this bike was run. After one of the longest resto's around I fired it up last week for the first time. It is a Smiths so I assume it's rebuildable. Is there anybody stateside doing that? Did I harm it by not having disconnecting it right away? I was hoping that some spin time on it would get it back in the swing of things, so to speak. One hour and the problem didn't resolve so I disconnected it.