Small Engines (Lawn Mowers, etc.): lawnmower trouble shooting, dirty fuel, fuel flow

Question
I start my lawnmower and it runs for a short time-maybe 10-15 minutes then it shuts down. I think it may be a dirty fuel filter but I'm not sure what it looks like and how to get it off. Any tips?  Thanks

Answer
Hi Bob,

First check the fuel cap to make sure it is allowing air to enter the fuel tank to prevent a vacuum as the fuel flows from the tank.  
Next, you will need to determine if the problem is a lack of spark or a lack of fuel flow.  Right after it quits, remove the spark plug, reconnect the wire and lay it against the engine head.  Pull the engine over and watch for spark at the plug's electrode.
If good, then try to start while squirting fuel or starting fluid into the carb intake.  If it starts, then the carb most likely has dirt, debris, gummed fuel or water inside.  You will need to remove the carb, disassemble it, clean all the small internal openings and blow it out with compressed air.   Probe each and every hole with a small wire.  A carb rebuild kit wouldn't hurt either.  Your engine probably doesn't have a fuel filter.

Let me know how you make out.
Michael