Small Engines (Lawn Mowers, etc.): carburetor problem - possible flooding, briggs stratton engine, briggs stratton

Question
I have a craftsman lawnmower with a 6 horse briggs & stratton engine.  The lawnmower was manufactured in 2003.  When mowing, not right away after the engine is warmed up, it seems to lose power, start running rough then dies.  After it dies I can't restart it. Acts like it is flooded.  Also I've noticed when it sets overnight gas leaks out of the carburetor not by the bowl but up by the air filter, like the float is not shutting the gas off.  We've replaced the valve needle and seat, the float and pin.  Still when left overnight gas still leaks out of the carburetor by the air filter.  Since there is no adjusting these carbs they seem simple but this one is giving us fits.  Any suggestions on how to stop the leaking.  I also assume this is causing the flooding while it is running.  Something isn't shutting the gas off.  Thank you.

Mike

Answer
Mike,

There is no advantage to installing two seats in the carb as it would end up leaking past them and you would be unable to set a proper float level because you wouldn't be able to bend the float height tang enough to make up the distance taken by the extra seat.  One properly installed seat will suffice.  Make sure you bottom the new seat  correctly in it's position with a pin that is just slightly smaller in diameter than the seat (non-cutting end of a drill bit will work) and make sure there is no debris under the seat before installing it.  Set the float height so the float sits parallel to the float bowl mounting lip (check by turning carb upside down).  If you have a plastic float rather than a brass one (which you can bend the tang to adjust), you will have to assume the float height is correct with the seat properly installed.  Hope this helps.


There must still be an issue with the needle and seat and/or float and/or pivot.  These are the only things responsible for controlling the fuel level in the carb.  That is likely causing the running problem as well (you should notice some black smoke from exhaust too).  Let me know what you find.  Hope this helps.