Help...ZX7R Tacho Issues...Help

Hi all,
Was hoping someone out there may be able to help..
Pulled the dash out of a zx7r and put my old race dash in..Which was working fine when last used.(also from a zx7r)
The problem I'm having is the tacho is reading approx double the revs...
I have plugged the tacho from the original dash back in and it seems to be displaying a true indication of revs..
So do you think the tacho is buggered or may need recalibrating....
Also does any one have a tacho like the one in the pic lying around there shed just in case i need another one...
I believe it is out of an earlier model ZXR
Thanks Maddog
Was hoping someone out there may be able to help..
Pulled the dash out of a zx7r and put my old race dash in..Which was working fine when last used.(also from a zx7r)
The problem I'm having is the tacho is reading approx double the revs...

I have plugged the tacho from the original dash back in and it seems to be displaying a true indication of revs..
So do you think the tacho is buggered or may need recalibrating....
Also does any one have a tacho like the one in the pic lying around there shed just in case i need another one...
I believe it is out of an earlier model ZXR
Thanks Maddog