Here are a couple of things you should check if you have a poor running unit or the vehicle is hard to start.
a. There is a black thick fiber gasket between the carburetor and the intake manifold. Check the gasket to make sure it is not cracked or broken. If this piece is cracked or broken, the carburetor will be sucking in too much air and will run lean.
b. Make sure the O-ring in the carburetor mount area is present and that the O-ring in the gasket between where the intake and the gasket mate. Sometimes these O-rings have been left out and will cause poor running or hard starting.