Small Engines (Lawn Mowers, etc.): Lawn Mower will not turn over, briggs and stratton, float bowl

Question
I have a MTD 21" Lawn Mower with a Briggs and Stratton 5.0hp engine.  I just recently replaced the blade, spark plug and air filter.  I was able to use the mower 2 times after this change.  Now I tried to start the mower and it will attempt to start, but will not stay running for more than 10-20 seconds.  I loosened the screw under the carburator, but could not figure out how to get it off to clean it out.  Do you have any ideas what I can do?  

Answer
Hi Charlotte,

It sounds like a fuel flow problem.  To confirm, try to keep it running with a choke, if equipped or by squirting fuel into the carb opening.  The carb may have dirt, debris or gummed fuel inside.  With the carb float bowl high speed mixture screw removed, the bowl will pull off.  It may just be sticking to its sealing ring.  You could try adjusting the carb mixture screws first but usually the entire carb needs to be removed, disassembled, and cleaned internally.

Let me know how you make out.
Michael