I once had some clocks that looked identical to that and were fitted to my CB750, whilst the originals were away for restoration.
The speedo was fine and, as with yours the tacho red line was incorrect. However the most concerning thing that I found was that the tacho readings were out by a huge amount, often several thousand rpm.
When I refitted the originals, I gave them away to a member of this forum who, like me wanted them for a temporary fit.