my push mower will crank but it will not stay running what is wrong with it?

most probably a simple fuel starvation caused by dirt or old fuel in the carb.
-for carbs with float bowls (honda, tecumseh, some briggs, some mountfields) -remove the carb, remove the bowl/float+needle/main jet, blast the whole lot with carb cleaner and if possible finish with a blast of compressed air over all the carb parts and the carb itself including through all the openings in the carb, then reassemble.
-for briggs classic with the tank top plastic carb, you need to replace the carb diaphragm.
this should get ya going again.
this problem is usually caused by dirt blocking the main jet on carbs with floats and bowls. or caused by an old worn or baggy carb diaphragm on the briggs.

Andy Lee
June 2009