First thing to check is the linkage from the carb to the governor arm. Kohlers have a plastic bushing that snaps on the linkage wire, may have come off. If everything is connected, look at the direction that the governor arm rotates the governor shaft when the throttle is moved to full open throttle. Loosen the bolt at the bottom of the governor arm, and rotate the shaft in the same direction that it turned when moved to full throttle while holding the throttle at full throttle. tighten the bolt on the governor arm, and retry. If still not fixed, then most likely the internal governor gear is broke, and will require engine internal work.