Starts right up then stalls

If its a Briggs and Stratton sprint or classic etc with the plastic carb that's screwed to the fuel tank then there's a good chance the diaphragm needs replacibg . it could just be that there is a lot if dirt blocking the pick up pipe but to clean it you will need to remove carb from tank to blow it out so for a very small amount of money you may aswell fit a new diaphragm while the carb is off. Drain the fuel tank and blow it out while carb is off to remove any dirt. Its an easy diy job that only takes 15 mins from start to finish, does help if you have an air line tho!!!

Before you remove anything remove that little brass nut at the bottom of the carb and check the little small holes in it for possible plugging. If all good there then proceed with what others suggested

Carb needs to be rebuilt

Heather:

The gas is not getting through the carburetor fast enough to keep the machine running. If you are not mechanically inclined, have a friend (who hopefully knows what they are doing) adjust the carburetor fuel/air mixture screws. You will need a small flat tip screwdriver. There are two small screws right next to each other sticking out from the carburetor (where the fuel lines hook into) GENTLY tighten those screws (remove the plastic caps if you have to). DO NOT OVER TIGHTEN THEM, BE GENTLE. Then loosen each screw one and a quarter turns out. The machine should run even if it runs poorly. When the machine runs, adjust each of the screws in or out until it runs properly. put the plastic caps back on the screws.