150CC very sluggish when reving up
 

i have 2 150cc motors that take their sweet time to ever build up rpms one is a hammer head twister that was froze up when i got it but i got it freed up and its sluggis and smokes of course but what has me stumped is the howit 150 thats been freshly rebuilt and has a known good carb on it....the hammer head i could sorta understand but the fresh motor just has me stumped on what causing it to take so long to build up rpms.
Its the same even with the belt off and no load what so ever.

Valve adjustment? cam timing? Jetting? Stuck choke/enrichening circuit?

valves are fine timing is fine ive tried jets from 125 all the way down to 110 choke is fine. stock exhaust with uni filter also tried open exhaust

CVT problem?

Slider or roller stuck?

Variator or driven pulley stuck open?

unless something is over torqued binding up the cams/valves or crank, sounds like a fuel/carb issue