Why doesn't my lawn mower start?

About a week ago I was trying to mow my lawn and the lawn mower turned off after 3-5 minutes of it running. I would start it up again and the same thing would happen. I took apart the carb and cleaned the bowl and jets with carb cleaner. The bowl gasket looks to be just fine. The spark plug is getting spark. I replaced the gasoline with fresh gas. Now it doesn't start. Please help.