Lawn mower wont start. Suggestions?

Here's what i've done so far. New gas, new air filter, cleaned gas lines, new spark plug, oil level fine. The mower turns over then dies. The last time it ran, it kind of sputtered a little (3-4 minutes) then ran fine. This time, I can't get it to run. It seems like it wants to run but like I mentioned it turns over like it wants to run, but dies. Anyone else had this problem and what did you do? Thanks.