Briggs and Stratton running rich.

Mower would not start. Purchased new carburetor from local John Deere parts store. The new carb is a replacement carb for the original and has no mixture adjustment. I can tell the engine is running rich. If I remove the vacuum line from the fuel pump the motor runs great until it runs out of gas. If i pinch the fuel line it runs great until it runs out of gas. any ideas?

Make sure the oil isn't contaminated with gas. the fumes can get drawn through the breather system into the intake just below the air filter and cause a rich run situation.