[spldart]

Carb leak.
Primary possibility is what blaine said.
Secondary is bad seal bowl to carb body. (rubber gasket in groove on bowl bad?)
Third. Expensive mechanic didn't set float right?
Forth. Some crap in rescued gas tank fouled the needle seat seal and now gas seeps constantly?

All these causes can cause run ability issues. Though they usually effect all temp starts...

The thing with cold starts, the colder the more the issue, is getting the mixture fat enough and a
a bit more of that rich mixture by volume.

Engine static ambient temp warm day start.... Do you use choke?

If it's 78 degrees or warmer out and I want to start my bike dead cold I just crack the throttle and crank.
No choke. It just springs to life.