First, you engine is 9 years old, not a newer mower. I’m going to ask a few questions to get a better picture of what is happening.
1. Have you recently tipped the unit on its side?
2. If yes, was the carb up or down?
3. Have you tried starting and running without the air cleaner?
4. What color smoke and does it clear up after running?
5. When you cleaned carb, did you check float level?