How is the high speed? Will it stay running at wide open throttle? I'd adjust the high speed needly just a click or two at a time until you get maximum RPM then back it off 2-3 clicks or until you get a 200-300 RPM drop. Adjust the idle screw 1/8-1/4 turn at a time until you get a smooth idle and good throttle transition. I've found most idle screws set too rich from the factory.

Another thing to try is a pinch test. Pinch off the fuel line and listen to the engine. If it speeds up before quitting, it is rich. If it dies immediately, it is lean. If it slowly starts to sputter and die, it is pretty close. That will get you in the ballpark at least.