runs great, but very hard to start. hot or cold

[clueless]

I have checked the valves, new carb, new plug, new cdi, new coil, new stator and getting fuel. when it is cranking and you give it just a hair of gas it bog the cranking down, almost stops it. once you get it running, it runs great! carb is adjusted. I am at a loss with this one! any help would be greatly appreciated!!

this is a 49cc tao tao atm-50a no mods