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Does the governor appear to move freely and vary the speed widely when you move it by hand?

Unlucky320 said:

I have a riding lawn mower with a Briggs and Stratton engine. Engine number 407777-0121-E4. When I start the mower it goes to full speed. Changed the carb on it cause it had a hole in the bowl, still doing the same thing. From what I've read online it could be the governor. Did try to adjust the governor on mower but it moves little, not like they show on the videos I've watched. Any help would be greatly appreciated.

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I don't believe that a governor would typically just go "out of adjustment" on its own. It is more likely that a governor spring is weak or broken or that the governor itself is bad. I had a similar issue years ago with my Briggs V-Twin and every time I started the mower it would literally rev to the ceiling. When I pulled the oil pan off the engine I found my governor in pieces. I attempted adjustment after adjustment and it never worked. Did you by chance experience any surging issues prior to the engine running away on you?

seattlepioneer said:

Does the governor appear to move freely and vary the speed widely when you move it by hand?

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The governor doesn't really move much to adjust it, (like what you see it does in the youtube videos I've watch online) we put a spring on it and it will slow down at the beginning but when you go to move the speed throttle it goes back to full speed.

Unlucky320 said:

The governor doesn't really move much to adjust it, (like what you see it does in the youtube videos I've watch online) we put a spring on it and it will slow down at the beginning but when you go to move the speed throttle it goes back to full speed.

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If all governor linkage and springs are on and set right, It's probably the governor assembly itself inside the engine. Seems like those are plastic and get brittle with all the hot/cold, hot/cold of a mower engine, and break!