The Mechanical Governor basically consists of two balls of equal mass, attached to the arms. The rotating ball is also termed as governor balls and fly balls. These balls are well attached to the arms and tend to revolve with the spindle.
The upper end of these arms is well attached to the spindle, which allows the ball in their up and down movement while revolving on the vertical axis. From below the arms are linked to the sleeve which is also keyed to the spindle and is allowed to revolve with the spindle. The sleeve is also allowed to slide up and down while revolving.
With the increase of speed, the balls and the sleeve rises up and tends to fall down with the decrease in speed. The up and down movement of the sleeve is controlled by stopper on the spindle. The sleeve is connected to the throttle valve with a bell crank lever. The supply of the air-fuel mixture increases when it falls and decreases with the rise of the sleeve.