99 tach problems

I purchased an old race bike and the guy gave me some gauges for it but it won't register past 4000 rpm and doesn't show proper idle rpm. I've checked tank sensor connector and exup valve connections and no problems. temp gauge works as well as speedo. any suggestions?

Can you give us some more information?

Need to check the wiring loom...there is a seperate piece of wiring that leads to the cluster (with feeds for the flashers and the front lights)