Scitsu rev counter help

Hi guys I have a 2001 carb sv fitted with a Scitsu rev counter witch is not reading correctly. It reads 8000 rpm on idle and only shows revs up to 10000. Thinking the rev counter was faulty i bought a new Koso rev counter to find its reading exactly the same. The bike is running perfect on both cylinders. Any advise on how to fix the would be great (its doing my head in)

Cheers Bryan