I have a snapper with a Briggs and Stratton 6.75 HP mower. I am having starting issues. It does not seem to want to fire up. I bought a new spark plug today. I also removed the carb bowl And dumped out the fuel. Looked cleaned. Reinstalled fire right up no issues. Thought it was fixed. I mowed front lawn. Then refired up amd no issues. Shut it off again to dump bag. Then refired right up. Mowed some more. Shut down to empty bag. Now it won't refire. Any ideas? I also have had hard start issues in the past month or so.