I'm not sure if anyone else will try to answer this one, but if your machine has a Briggs and Stratton engine, with the fuel tank below the carburettor, there should be only one spring loaded screw. With the engine running fast, turn this screw clockwise until the engine runs cleanly - but only just! If you overdo it, the engine will be down on power and is likely to stall.
John, May 2009
