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*Always follow the instructions in your repair manual when doing repair or maintenance work on Outdoor Power Equipment. Manuals can be found at the manufacturers website.*

The 25HP Vtwin Kohler engine fitted with a carburetor uses a centrifugal flyweight mechanical governor. The governor is designed to hold the engine speed constant under different loads. The bulk of the governor is contained inside the engine crankcase and is gear driven by the engines camshaft.

This is how the governor works. The flyweights on the governor move outward by centrifugal force as the engine speed increases. The higher the engine speed, the higher the centrifugal force acting on the flyweights. As the flyweights move outward, they turn a shaft called the cross shaft, which is connected to the governor arm. The governor arm is located outside the engine and is connected to the governor spring and the throttle valve on the carburetor. The governor spring force always tries to hold the governor arm and throttle wide open. When the engine reaches a speed where the centrifugal force on the flyweights and turning force on the cross shaft is equal to the governor spring force, than the engine will stabilize at that engine speed. The governed speed of the engine is always the point when the centrifugal force on the flyweights and turning force on the cross shaft is equal to the governor spring force. When the engine encounters a load, the engine slows down, and less centrifugal force is acting on the governor flyweights and thus less force is opposing the spring force. The spring is always trying to force the throttle open, so as the engine slows down and creates less centrifugal force on the flyweights, the governor spring forces the throttle open. This permits more fuel to enter the engine and increase the engine RPM. As the engine RPM increases, the centrifugal force on the governor flyweights increases until the force created by the flyweights acting on the governor arm is equal to the governor spring force. This back and force continues until a balance is reached and the engine stabilizes at a constant RPM.

Adjusting the governor arm and cross shaft is a simple job. You simply loosen the nut that holds the governor arm to the cross shaft. As the nut is loosened, hold the governor arm as far toward the carburetor as possible, and turn the cross shaft counter clockwise until it stops. When both the cross shaft and governor arm arm in this position, tighten the nut that holds the governor arm to the cross shaft. That is all there is to it. Kohler drilled a hole in the end of the cross shaft to make it easier to turn the cross shaft. Kohler recommends using a nail, but I found it easier to use a 90 degree pick.

Tools Used:
90 degree pick
8 and 10 mm socket
Universal Joint
Ratchet and Extension