Honda VFR 750 gen 3 1992. Tachometer shows to high rpm.

After quite a long trip, about 600 km's over 2 days, the tachometer suddenly showed around 1-2k above the usual rpm after the bike had been parked for a little bit. I searched the forums, but couldn't find any other posts with this issue.
Any suggestions on a fix would be greatly appreciated.

 

Is the tach showing the wrong rpm or is the engine revving at that rpm?

 

Tach was showing wrong rpm. The pin went way above the redline under acceleration, and it was about 2k higher than usual during normal cruising and 600-1000 higher during idle, when i started it the first time i happened the idle rpm was around 2000 on the tach, but the engine sounded like it used to, but i tried adjusting the idle screw to around 1250 ish, but then the bike just stalled. So it was definetly the tach showing the wrong rpm
But i started the bike not to long ago again and the fault seems to be gone again. So now i have to wait and see whether it comes back or was a one time thing.