Hi All . I Have a thunderace sitting In my shed that I brought a number of tears back , the exhaust system had been replaced by the previous owner and the Exup valve removed . The issue is that it accelerates hard up to about 7000 rpm then will not rev past that  ..Any ideas where to start ? 

Thanks 

If its been sitting in a shed for some years, then id guess that the carbureters require cleaning out as the fuel will have gone off in them

Hi there , sorry cleaned carbs ,flushed tank etc , new plugs as well still just stops revving at that point , I'm assuming that's the same Rev area the exup valve would start to do its thing so wondering if there is something sensor wise stopping it ? , it's not a flat spot you can get past it just dies there. Cheers 

Did you get this issue sorted?

The exup was for low rev power, it shouldn't cause this.