How does a speed govenor work?

Answer 1

A governor system behaves like an unending tug of war between one of two governor springs, which pull the throttle toward the open position, and a spinning crankshaft, which tries to close the throttle. When the load on the engine increases - a typical example is when you move your running lawn mower from the driveway to the grass - crankshaft revolutions drop. But the governor spring is still tugging, causing the throttle plate to open.

In response, a larger volume of air-fuel mixture enters the carburetor, increasing engine speed to compensate for the increased load. The crankshaft speeds up, and the tug of war resumes, until a new equilibrium is achieved. With each change in load, the tension between the governor spring and the load brings about a new equilibrium, known as the engine's governed speed.

Neither side wins until the engine is shut off. At that point, without the crankshaft spinning, the governor spring pulls the throttle to the wide-open position.

Two types of governor are common on small engines - mechanical and pneumatic.