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  1. #1

    Join Date
    Jun 2012
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    briggs & stratton 300 series

    problem with my Briggs & Stratton 300 series

    model # 961140014 05 runs, but not smooth. It runs high then low, high then low continuously; like it wants to shut off

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  3. #2

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    kioti/rhino finish mower

    Re: problem with my Briggs & Stratton 300 series

    Either the carb needs cleaned or if it has the two spring governor system, then springs may need adjusted to syncronize them
    ILLINOIS ENGINE, BEECHER CITY, IL
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  4. #3
    doug9694's Avatar
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    Nov 2014
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    Michigan
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    11 Hp Craftsman, 6,25 Briggs self propelled

    Red face Re: problem with my Briggs & Stratton 300 series

    The problem with these carbs are they are plastic. Over time they form a gap under where the carb slides on the intake tube.
    This causes too much gas to go directly into the engine causing rough running. I have seen such wide gaps that the otherwise good diaphragm gets folded in and is ruined in some cases. I have reused them by putting a weight on them over night to flatten it back out. I have tried filing the carb flat. that did not work.
    The fix I used is to put two long studs in. One on each side, and a bent 1/8" x 1/2 thick bar with a hole that goes on the stud and screw a nut down till you see the gap closing. Let it set awhile and screw down some more as the carb takes a set.
    Then screw a nylock nut on the first one. The mower ran like new when I put the carb back on. Cut any extra off the studs so they don't interfere with the air cleaner.

  5. #4
    BriggsStratton's Avatar
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    #PoweredByBriggs

    Re: problem with my Briggs & Stratton 300 series

    Hi there, only1divine!

    It could be one of two issues from what I can tell. I was unclear if it was a surging problem or a losing power problem so I'll give tips for both cases.

    An engine losing power under a load could be caused by a few things including carbon build-up on the head, valves not seating properly, intake manifold air leak, or even a blockage in the carburetor or a diaphragm that needs to be replaced. I'd suggest you start by replacing the diaphragm.

    Surging can be caused by one of two things: either a dirty carburetor or the governor needs to be adjusted. You can clean the carburetor. Here's a link on how to do that: bit.ly.
    If the surging still persists after you clean the carburetor, try adjusting the governor. Here's a link that will help with that: bit.ly. Let us know how it works out!

  6. #5
    doug9694's Avatar
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    Michigan
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    11 Hp Craftsman, 6,25 Briggs self propelled

    Re: problem with my Briggs & Stratton 300 series

    Quote Originally Posted by BriggsStratton View Post
    Hi there, only1divine!

    It could be one of two issues from what I can tell. I was unclear if it was a surging problem or a losing power problem so I'll give tips for both cases.

    An engine losing power under a load could be caused by a few things including carbon build-up on the head, valves not seating properly, intake manifold air leak, or even a blockage in the carburetor or a diaphragm that needs to be replaced. I'd suggest you start by replacing the diaphragm.

    Surging can be caused by one of two things: either a dirty carburetor or the governor needs to be adjusted. You can clean the carburetor. Here's a link on how to do that: bit.ly.
    If the surging still persists after you clean the carburetor, try adjusting the governor. Here's a link that will help with that: bit.ly. Let us know how it works out!
    Replacing the diaphragm is a waste of time and money if the gap as I explained in the previous post is not taken care of.
    Even those after market ones that are thicker in that area may not fix the problem. Depends on the size of gap. I have measured 0.025". The two best ways is: 1, A new carb. 2. The hold down as described in the previous post.
    If you use the hold down you will not have this problem re-occurring, even if you buy a new carb, in a couple years.

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