# Sudden Engine over-revving Kohler 7000 series



## John Maul (Aug 17, 2020)

I was mowing and experienced sudden high rev of the engine to the point where I had to shut it down. I was able to feather the revs by applying the choke and driving back to the barn. I thought that the governor may have broken or that the throttle linkage was jammed.
After removing the air shroud ,I cleaned some debris from the linkage area but found no real interference. The carb was retained by the same screws as the air shroud and came off the studs with ease. The throttle linkage popped out of the carb body and I saw that the throttle shaft had snapped at the upper butterfly screw hole. The valve was stuck in the full open position and must have caused the over revving. The upper screw is missing and I assume it was sucked into the engine. I hope I can vacuum the screw out but may have to live with it somewhere in the intake or exhaust runners.
Can the throttle shaft & screw be replaced or do I have to replace the entire carb ?? By the limited info that came with the mower, the carb appears to be a Walbro one barrel with fixed main jet. Reference is made only to Kohler carb and an on-line view describes the shaft by #12 144 09-S and the valve screw by # 25 086 27-S. Can these parts be ordered separately or in a kit ?


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## Bob Driver (Nov 1, 2017)

It's not uncommon for a butterfly screw to come loose. The two kohler part #'s means you buy them separately. They'll run less than $20 wholesale(genuine Kohler). A complete aftermarket, Kung Fu carb for a 7000, runs about $50 on Amazon.

It's only a matter of undoing 4 screws, throttle/choke links, and the whole intake manifold comes off. The throttle link has a plastic clip on the rod and a small surge spring that needs to come loose. You'll need to slightly twist the entire manifold assembly get the the choke linkage loose from the control plate. 

You really need to get that screw out of the intake, or you run the risk of it jamming the intake valve. Either suck it out with a shop vac, or use a magnet if it's not a brass screw. If that fails, slowly roll the engine over until the valve is closed and see if you can blow it out with a burst of shop air. I've even used a Q-tip with a wad of axle grease on the end to fish them out.

Make sure the butterfly plate isn't bent. Drop some blue Loc-tite on the threads and install both screws, but keep them 1/2 a turn loose. Close the throttle plate to center the butterfly and then tighten the screws. Make sure the butterfly works smoothly before you put the carb back on the machine.

If the screw got all the way into the valve chamber, I would pull the valve cover and make sure the intake push rod is straight and run a compression test to make sure the valve face/seat seal didn't get damaged.

Hopefully, you got lucky and there is no real damage.


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## John Maul (Aug 17, 2020)

Thanks Bob, 
I found a used carb locally and used the shaft & screws from that. everything went together and seems to work freely. When I started it up, the over rev happened again. I suspect the internal governor may be the culprit. I was able to choke the engine to keep the revs down and finish mowing the half acre unmowed. The local guy that had the carb said if the engine ran for more than a minute without issue, the screw probably passed thru the exhaust and out of harms way. I don't want to tear the engine down at this point so It'll wait.


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