Small Engines (Lawn Mowers, etc.): Lawnmower Trouble shooting, briggs and stratton, internal passages

Question
Hi Marc- I have a push mower (Sears - small mower - circa 1995, Briggs and Stratton engine) that runs for about three seconds after I pull start it, then dies. I pull start it, it revs real stong, then it just stops. I have replaced the airfilter, gas plug, and did an amature job at rebuiling the Carb. (at least it still starts for three seconds intervals even after I rebuilt the Carb - so I did not mess anything up there). I have also pulled off the muffler, and the engine still starts for the three second interval, so the muffler is not clogged. It just seems like there is some sort of a regulator that is not tuned right. Can you suggest what may be wrong? Why won't it keep running?

Thanks,
Eric

Answer
It is likely that either the tank vent or the carb has a blockage.  First, try loosening the fuel cap off a bit and starting.  If this corrects the problem, you will need to clean / replace the fuel cap (vent in cap).  If not, you will need to thoroughly clean the carb, including pushing a piece of tag wire through all of the internal passages and following up with aerosol carb cleaner.  Hope this helps.