Kohler 22 hp 7000 Series KT725-3078

[Shootertexas]

I need ya'lls help again.

After replacing the rectifier, oil, oil filter, fuel filter and air cleaner it ran like a top. My friend came and got it and he went to mowing the grass at the church he pastors.
It ran according to him, great for about 45 minutes, and all of a sudden it went into and extreme over speed condition. He immediately ran it up on the trailer, about 45 seconds after it started the over speed and killed it. Somewhere in between the time it started to over rev and the time he got it on the trailer he disengaged the blades and it threw the belt off.

I have it now and am trying figure out if its an internal or external problem. I don't believe the servicing had anything to do with it as nothing on the linkage was touched.
I have looked and the governor shaft coming out of the engine and and it appears to move with the lever so I believe it is tight.
There is however some in and out movement of the governor shaft, is that normal?

Probably a long shot but I was contemplating taking the cover off the carburetor to see if possibly the butterfly fell off the throttle...maybe a stupid idea.

I will say the throttle cable is very had to move, so much so he broke the paddle off and there is only a nub sticking out to try and move the throttle.

 

[Scrubcadet10]

Disconnect the governor spring and throttle shaft link rod (that goes from the governor arm to the carb), start the mower, manually increase the engine speed by opening the throttle valve, you should see the governor arm move towards the closed position as the engine speed increases.
The governor and governor spring are in a tug of war, the governor tries to slow the engine, while the amount of tension you put on the governor spring via the the throttle cable tries to open the governor, and in between that you get a constant RPM.

 

[StarTech]

Probably a long shot but I was contemplating taking the cover off the carburetor to see if possibly the butterfly fell off the throttle...maybe a stupid idea.

Not at all. I had Courage earlier this year where both vane retaining screw came out and was on top of the piston. I also had Kawasaki v-twin that lost one its vanes the same way.

 

[Shootertexas]

Disconnect the governor spring and throttle shaft link rod (that goes from the governor arm to the carb), start the mower, manually increase the engine speed by opening the throttle valve, you should see the governor arm move towards the closed position as the engine speed increases.
The governor and governor spring are in a tug of war, the governor tries to slow the engine, while the amount of tension you put on the governor spring via the the throttle cable tries to open the governor, and in between that you get a constant RPM.
View attachment 58242

The governor arm does not move in either direction. I would assume the arm, with no springs attached, would move in either direction as the counter weights move in and out,

 

[StarTech]

The governor arm does not move in either direction. I would assume the arm, with no springs attached, would move in either direction as the counter weights move in and out,

You have a misunderstanding of how most small engine governors are designed.

The governor bell crank rides on a push pin and it is the governor's flyweights that moves this push pin which in turn pushes against the bell crank. When springs are removed the bell crank freely moves but does not move any part of the governor.

Now if you are unable to move (rotate) the bell crank then either there is bind in the throttle linkage, the throttle vane assembly, or in the bell crank bushing.

 

[bertsmobile1]

In any case, all this is achademic.
Run away engine = failed governor
so unless the governor arm is very loose on the governor shaft ( does happen even with new engines ) , it is an internal governor failure .
So get a torch and try to move the governor arm while watching the shaft
If they move with respect to each other reset the governor
If they move together or do not move at all then it is out with the engine .

 

[Shootertexas]

You have a misunderstanding of how most small engine governors are designed.

The governor bell crank rides on a push pin and it is the governor's flyweights that moves this push pin which in turn pushes against the bell crank. When springs are removed the bell crank freely moves but does not move any part of the governor.

Now if you are unable to move (rotate) the bell crank then either there is bind in the throttle linkage, the throttle vane assembly, or in the bell crank bushing.

I probably described it wrong.
With the engine running, the bell crank does not move at all from either position (full on or off) at any speed with or without the springs on.
I'm assuming the push pin has fallen off or if it is like most things now days, the governor gear is made of plastic and has quit engaging the crank gear.
I'm leaning on the push pin falling off at this time. There is probably 3/8 of an inch play in and out on the cross shaft.

 

[StarTech]

I probably described it wrong.
With the engine running, the bell crank does not move at all from either position (full on or off) at any speed with or without the springs on.
I'm assuming the push pin has fallen off or if it is like most things now days, the governor gear is made of plastic and has quit engaging the crank gear.
I'm leaning on the push pin falling off at this time. There is probably 3/8 of an inch play in and out on the cross shaft.

Then most likely the push pin off as that is a lot play and the bell crank tip isn't that wide.