Kawasaki FH680V CS13V over revs with governor linkage adjusted properly

Magnetic reed switch near output is probably bad. Look for coil behind front panel, there is a small glass tube inside, with 2 small wires.

Do you have governor adjusted properly? Possibly "PidStu" question, but you'd be surprised how many I've seen. Can you move the governor linkage arm with your fingers or does it seem to be locked in position? If it is locked, it is adjusted improperly.

Check that the rev governor/throttle cable adjuster screw has not slipped out of adjustment (lock nut vibrated loose).

The throttle plate is spring loaded to pull wide open, opposed by the governor which will pull the throttle closer to closed when the limited or specified rpms are reached. If the governor arm does is not connected to the throttle bell crank(linkage broken, off, or missing), it can't pull the throttle closed. If the arm does not move to close the throttle, the governor is likely broken inside the crankcase. or needs adjustment. The internals are a spool that moves based on rpm, pulled up by flyweights that has the external governor arm shaft 'trapped' in between the spool 'ends'. The spool will move the shaft and in turning, move the arm to pull the throttle closed. You adjust the arm on the shaft so the governor can pull the throttle completely closed with all the slack taken up.

adjust governor its not the fuel

This problem may SEEM carb related, but it is probably a result of bad linkage to the governor (controls engine speed) and may mean the governor needs adjusting (easy) or the linkage to the governor is stretched or not connected properly.

One possible cause for this problem is debris,sticking,or frozen linkage between the governor and the throttle butterfly. Depending on the make and model of your engine it will either be a mechanical governor that has a arm that goes down into the case or a air vane governor that is behind the recoil shroud of the engine. Move all the linkage that connects between the governor and throttle and speed lever to make sure it doesn't bind or sticks. If it does pray a little silicone or wd 40 spray on it to help reduce friction. Also on air vane governors they can become stuck from debris that inhibits it from moving make sure there is nothing in the way of the governor. If all of the linkage is working properly and you still have the issue try adjusting the the fuel mix screws and the high rev. settings on the throttle lever (if equip.).

It sounds like the Governor on the engine is out of whack. Maybe a spring that controls the governor broke off, or the linkage to the carb is stuck. Maybe there's dirt and grim keeping the linkage from moving freely.
To better understand how the Governor works and how to adjust it, you can Google " small engine governor". There are several web sites which have helpful Info.
Hope this helps...