hello , i have a problem with my engine cvh1600 .

the specs are :

- cvh1600 xr3i stock bottom end
- hemi head , ported
- rs1600i valves
- rs1600i springs
- newmancams mechanical followers
- rs1600i camshaf
- rs1600i exhaust manifold
- twin weber 40 , 36 choke , correctly jetted

the engin can't run under 6000 rpm and i don't know why ?

at the past i changed ignition , fuel pump , cam belts , plugs , etc etc all had change 3 times , but the engine continue to cut at 6000 rpm

help me , i don't know what is my problem

on this video you can listen the engine cut at 6000 rpm