gy6 150 surging at idle

having problems with this gy6 150 changed out the cdi,carb heads and cyl,spark plug,stator ,coil and intake manifold checked for vacuum leaks and compression everythings good.timing at TDC and cam dots aligned to the head. borrowed another motor just to see if any changes and its still the same..carb still surges and wont even open up WOT .diaprahm is good no tears carb all cleaned out all passages and jetting. running direct hose from the tank for direct fuel flow. tank vents clear no debri.. any help will be much appreciated