2002 Foreman Fourtrax won't take throttle

I have a 2002 400 with a new carb and a new petcock. starts fine and idles great. It won't take throttle to rev after start unless it idles a while. Carb screw is out 2 1/4 like manual says. Acts like it's not getting a sufficient supply of gas. Fuel line was replaced by a guy that worked on it. Don't get it.