Small Engines (Lawn Mowers, etc.): everything to fix it. Can you give me any information why this Briggs & Stratton, tipping lawn mower

Question
Hi, I have a Craftsman Lawn Mower model 917.378461 with Briggs & Stratton engine #123k07-0184-E1. I tilted the mower forward to clean the bottom (grass etc.) then I saw oil coming out of the air filter. So, I installed a new air filter and a new spark plug, then I started the mower and the engine ran at low RPM's for 15 minutes then stopped. Now, I can not restart the engine until the it is completely cold. To try to fix it I removed the carburetor and cleaned it with carburetor cleaner, then restarted the machine and it ran the same way it did before trying is happening, and what I can do to fix it? I would really appreciate it if you can answer me back. Thank you, Fernando.

Answer
Hello Fernando,

Number one suggestion, always tip the lawn mower with [the spark plug] side up.  Never tip a lawn mower any other way.  

This oil leak happened due to the tipping and nothing to do with the air filter.

You have to be careful with carb cleaner because sometimes rubber seals can get damaged by coming into contact with harsh cleaners.  The cleaner is good for only the metal parts [that's it!!]

Check to make sure the spark plug is properly gapped.  Check your owner's manual for specifications.

Let me know how it goes.

Howard