1980 KZ750 E1 Speedo and Tach

The Speedometer and Tach on my 1980 KZ750 E1 are very sluggish, I suspect this is due to the bike being outside under a cover for 10 years, I've replace both cables with the same result. Does anyone know any companies out there that do speedometer repair, I know these are sealed units, but trying to avoid purchasing new ones even if their available. For now I've purchased a mini tach which works fine, but like to use the originals. BTW everything on the speedometer works fine just very sluggish pointer reponse.

i'm thinking of using this place:

www.z1enterprises.com/reference/ZResto_home.aspx

Thanks, Just sent them an e-mail, seems alot cheaper than a new speedometer I just saw on E-Bay for 450 dollars.