Briggs and Stratton 11 Horsepower (Hp) engines use a two-piece Flo-Jet type carburettor. This type of carburettor is common on most Briggs and Stratton mid-range engines. Fuel enters from the gasoline tank into a small bowl assembly. The fuel in the bowl is regulated by a copper float. The vacuum from the engine compression system draws fuel up from the bowl and through a small diameter venturi tube. A needle valve regulates this fuel flow. At the top of the venturi tube resides the idle valve. Both the needle valve and the idle valve must be adjusted.
Locate the needle valve on the bottom of the fuel bowl assembly. Turn the valve by hand in a clockwise direction to seat the needle in the full-close position. Open the valve 1 1/8 turns in a counter-clockwise direction. This is initial carburettor adjustment.
Turn the idle valve, located at the topside of the carburettor inlet fuel tube, fully closed in a clockwise direction. The idle valve will have a single slot for a slot type screwdriver. Open the idle valve 1 1/8 turns in a counter-clockwise direction.
Start the 11 Hp engine as per the operational instructions listed in the engine. Allow the engine to warm for one-minute.
Pull the throttle handle to the high-speed position. Turn the needle valve in, clockwise, until the engine begins to sputter. Slowly open the valve, counter-clockwise, until the engine smooths out in operation.
Push the throttle handle back to the idle position. Adjust the idle valve in the same manner as described in Step 4. Once the two valves are properly adjusted you must be able to move the throttle handle from idle to high-speed and the engine respond smoothly.
Ensure the fuel tank is at least half full with fresh gasoline. Old fuel will cause sparkplug fouling and erratic operation from a properly tuned engine.