Small Engines (Lawn Mowers, etc.): lawn mower no start, carburator, cleaning solution

Question
Hello, how are you today, I have a murray 4007, 3.5hp mower that i got from a friend who has had it for years, it would not start so I replaced the spark plug and it spit some oil out, and then smoke but started on the first pull and would run for a good while before stalling, so I decided to replace the air filter which was dirty and clogged with debris, when I replaced the filter I decided to sharpen the blade with my dremel so i tipped it on its side with a brick under it and sharpened the blade when i went to try and start it it would not start, if I take the filter off and pour some gas into the carb, it will run for a few seconds and the cut off, new plug, new filter, what should I try next?
Thank you

Answer
 Hello Harold:

 Clean and Rebuild the Carburator. Over Time the Gas Forms a Varnish Inside the Carburator and Restricts the Flow of Gs Through the Jets. You May have to Let the Carburator Soak Overnight in Cleaning Solution to Really get it Clean. Hopr this Helps. Let me know what Happens, Please.

 Good Luck

 Respectfully

 John