Tachometer issues

1985 vf1000f runs great, but the tach needle seems to not want to go back to idle. To be precise, the motor goes down to idle, but the tach shows about 1000 rpm more than it is. Tap on the tach itself, and it sometimes drop down to the correct engine speed. Can’t figure out if its a bad spark unit or if there is something actually sticking in the tach itself. Any else seen this?

It will probably be the balance spring or shaft in the tacho that’s got a little corrosion on it…

Good thought. There doesn’t appear to be any. Out of the bike it returns to zero no problem. Put it back on, run the bike, it hangs up around 800 rpm with the engine off.