I have a "new", bought towards end of last season, Briggs and Stratton, 500 series, 140cc mower. I prime it, pull the cord, it fires for about 2-3 seconds, then dies. It will not fire up. I bought a new plug, checked and cleaned air filter, drained old gas and put new in, but still having the same issues. Need some thoughts here please. Engine repair is not my wheelhouse, but always learning here. Thanks