Kohler Courage 20HP SV601 - Overspeed, no throttle control

[cmayo]

Suddenly, my Kohler Courage 20HP (TroyBilt) is running flat out, revving well above its usual highest RPM. The throttle control has no effect and the throttle linkage on top of the carb (circled in red on drawing) seems to be frozen and will not move/pivot either by hand or with the throttle cable. I know absolutely nothing about carburetors (including the basics of what they do and how they work)... any ideas why this might happen and how/whether I can fix it?

 

[Auto Doc's]

The engine governor linkage has come loose, or the carburetor shaft is stuck from dust or debris and will no longer move. Try spraying the upper lever area with WD-40 lightly and let it soak in for a couple of hours, then get it moving and spray it a little more. Keep working it back and forth until it loosens up nicely.

If that does not resolve the issue....

A rare possibility is if the governor has failed and come apart.

My suggestion is to find a reliable and reputable independent local small engine mechanic before considering a regular shop. Regular dealer shops have a high turnover of people with little or no experience.

Edit:

As the reply following this one state, there is a chance one of the throttle blade screws came out and now it is jammed wide open. The intake will have to come off and the carburetor separated for inspection.

There could also be a chance that something got in the intake and made its way to the throttle plate to hang it open.

 

[VegetiveSteam]

Screws might have come loose and the throttle plate is wedged in the carb.