Lawnmower not working?

I have a Craftsman Briggs and Stratton 675 series 190cc lawnmower. If I try and start it, it will get really close and then die again. It already has full gas and oil so don't say I need those. I've replaced the air filter already and taken the whole air filter system off. I've also changed the spark plug and gas line. I left it outside a couple times and when I was gone it managed to accumulate 2 feet of snow on top of it but after that we had it working...it just won't work now. Any ideas?