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  1. #1
    Gold Member jcliburn's Avatar
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    Lawrence County, Mississippi
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    Kubota MX5100

    Default B&S portable generator governor

    I have a Brigss & Stratton Power Boss 5500 watt portable generator that recently began running wide open all the time. I suspect the governor has failed, but I have some questions for you folks before I get much deeper into this repair.

    In the first picture below, you can see the governor shaft (red arrow) connected to linkage that's tensioned by a spring (green arrow) which guarantees the throttle (blue arrow) is held wide open when the generator is shut down. In the picture, the throttle is wide open, and nothing changes when I start the generator.

    When I disconnect the linkage from the governor shaft, I can rotate the shaft freely within mechanical limits. The second picture shows the new governor, and the "mechanical limits" I'm referring to are presumably the flag contacting something inside the crankcase; I can hear a tap-tap inside as I rotate the shaft back and forth.

    Is it normal that the governor should rotate freely in this manner? Should I feel resistance? How does the governor "govern"? What's happening inside the crankcase to cause the flag to rotate to a certain position or stay at a certain position?

    Assuming I'm gonna have to tear into this beast further, the final three pictures show the engine, rotor, and bolts at the rotor end and flywheel end. Any ideas how to remove the rotor?

    Thanks in advance.

    Jay
    Attached Thumbnails Attached Thumbnails -governor-linkage-jpg   -new-governor-jpg   -whole-generator-jpg   -rotor-jpg   -flywheel-jpg  


  2. #2
    Gold Member jcliburn's Avatar
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    Lawrence County, Mississippi
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    Kubota MX5100

    Default Re: B&S portable generator governor

    I made enough progress to answer my own questions, so I'll post the results here for the next guy who comes along looking for the same or similar thing.

    First, to remove the rotor from the tapered engine shaft, I had to drive the rotor fan back torward the engine with a long drift punch. Once that was done, a couple of raps on the base of the rotor shaft with a ball peen hammer broke it loose.

    Once I got the crankcase cover off, I discovered that the governor is just fine (red arrow). I also discovered how the governor limits engine speed. Turns out there's a governor gear mounted in the top of the crankcase cover (green arrow).
    -open-jpg

    A close-up of the governor tab here shows that it's supposed to make contact with a shaft extending from the middle of the governor gear.
    -governor-tab-jpg

    This pic shows the governor gear shaft in the retracted, at rest position.
    -retracted-jpg

    As the engine rotates, the ears inside the governor gear spread open under centrifugal force, causing the shaft to extend outward, pushing on the tab inside the crankcase, which adjusts the throttle. This pic shows the shaft extended.
    -extended-jpg

    I finally found the engine model number stamped into the side of the valve cover. It's a B&S model 204412, type 0163E1, code 050804YD. Hope this helps someone else.

  3. #3
    New Member
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    Feb 2014
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    john deere 790

    Default Re: B&S portable generator governor

    Jay, I ran across this old post and wanted to ask, as I am experiencing the same problem. What actually did you find as the cause of high rpm on this generator?

    thanks
    Greg


    Quote Originally Posted by jcliburn View Post
    I made enough progress to answer my own questions, so I'll post the results here for the next guy who comes along looking for the same or similar thing.

    First, to remove the rotor from the tapered engine shaft, I had to drive the rotor fan back torward the engine with a long drift punch. Once that was done, a couple of raps on the base of the rotor shaft with a ball peen hammer broke it loose.

    Once I got the crankcase cover off, I discovered that the governor is just fine (red arrow). I also discovered how the governor limits engine speed. Turns out there's a governor gear mounted in the top of the crankcase cover (green arrow).
    -open-jpg

    A close-up of the governor tab here shows that it's supposed to make contact with a shaft extending from the middle of the governor gear.
    -governor-tab-jpg

    This pic shows the governor gear shaft in the retracted, at rest position.
    -retracted-jpg

    As the engine rotates, the ears inside the governor gear spread open under centrifugal force, causing the shaft to extend outward, pushing on the tab inside the crankcase, which adjusts the throttle. This pic shows the shaft extended.
    -extended-jpg

    I finally found the engine model number stamped into the side of the valve cover. It's a B&S model 204412, type 0163E1, code 050804YD. Hope this helps someone else.

  4. #4
    Gold Member jcliburn's Avatar
    Join Date
    Apr 2009
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    282
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    Lawrence County, Mississippi
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    Kubota MX5100

    Default Re: B&S portable generator governor

    Hi Greg,

    After all that work tearing that generator apart, the problem ended up being that the governor shaft had simply slipped inside the arm that connects it to the throttle. Wouldn't even have had to disassemble the engine if I had only recognized the problem correctly in the beginning.

    In my first post above, the first image in that post has three arrows: a red, a green, and a blue. The problem occurred at the red arrow, where the governor shaft connects to the throttle linkage. The shaft had somehow slipped (rotated) inside that clasp. To fix it, i loosened the clasp nut, rotated the governor shaft as far as it would go, then tightened the nut.

    Jay

  5. #5
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    john deere 790

    Default Re: B&S portable generator governor

    Thanks Jay,
    I was thinking governor shaft. I will give it a go!

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