Glenn, if the engine speed cycles continuously, say every 2-5 seconds, that is called "hunting" and is usually caused by lean mixture. (It can be due to friction or jamming in the governor mechanism, but that is relatively unusual.) Your carburetor appears to be a small two piece Flo-Jet, and the main mixture adjustment is the screw that sticks out from the lower left of the float bowl at a 30 degree angle to the vertical. With the engine running and hunting, turn that screw anticlockwise a quarter of a turn and wait a few seconds to see what happens. If it still hunts turn it the same way another quarter turn. If it still hunts after that, you are going to have to look for a fault: either an air leak or dirt in the carburetor.
Last edited by grumpy; 09/10/12 10:22 AM. Reason: Add detail
