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Hot!Briggs and Stratton 311777

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Jfhunter64
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2018/06/23 14:57:04 (permalink)
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Briggs and Stratton 311777

Hi all. First post here. I'm hoping this isn't as bad as I think it is but here we go. I work got a free mower that 'had not run for over 2 years' according from the previous owner. It was not running (no fuel) so I changed out lines, fuel filter, and put new a new needle in the walbro carb and gave it an over all cleaning, new gaskets, etc. was running fine for a few weeks but its now missing from what I can tell. Not a smooth run, almost like I can hear the individual firing on the piston... Well I checked the plug, which is also brand new, and its black... Oily black... Oil level fine. Could I have gotten the wrong gaskets? I did fine rubber fro the gas cap in the gas tank which was clogging things up... But thoughts on the misfiring and oily plug. I'm sure they are related.

Thanks in advance ,

John

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    Roy
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    Re: Briggs and Stratton 311777 2018/06/23 21:16:10 (permalink)
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    Did you have the head off? It is important to use the correct head gasket, the one for the 330000 series will fit but the quench area is too large. It is also important to correctly torque the head bolts in the proper sequence. The 276781 manual is your friend.
    Jfhunter64
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    Re: Briggs and Stratton 311777 2018/06/23 22:42:01 (permalink)
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    I never took the head off. I took the air filter box off, the carb, and the largish hard plastic tube that goes from the carb to the head.
    AVB
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    Re: Briggs and Stratton 311777 2018/06/24 06:45:17 (permalink)
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    I would replace the square cut o-ring on the intake; between the intake and the head.When bad the engine will try to condensate for the air leak by running the carburetor extra rich. I had one so bad year at doing this that engine would actually sneeze as if it had an allergy.
     
    Also it would not hurt to go ahead and change out the head gasket. This is because the 28, 31, and 33 series OHV have a head design that is prone to blowing head gaskets; especially between the cylinder and the push rod gallery.
     
    Now if you have a leak down tester and know how to use it you can check before replacement as it could save some time if the head gasket turns out to be good. During this test it is advised to the valve cover off so you can listen to the valve gallery as if the gasket is blown at the gallery it is leaking air will be louder at it instead of the crankcase fill tube.
     
    The cylinder head torque was increased to 250 in lbs using three stage step torque, previously it was 220 in lbs.
     
     
    Jfhunter64
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    Re: Briggs and Stratton 311777 2018/06/25 10:29:50 (permalink)
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    AVB
    I would replace the square cut o-ring on the intake; between the intake and the head.When bad the engine will try to condensate for the air leak by running the carburetor extra rich. I had one so bad year at doing this that engine would actually sneeze as if it had an allergy.
     
    Also it would not hurt to go ahead and change out the head gasket. This is because the 28, 31, and 33 series OHV have a head design that is prone to blowing head gaskets; especially between the cylinder and the push rod gallery.
     
    Now if you have a leak down tester and know how to use it you can check before replacement as it could save some time if the head gasket turns out to be good. During this test it is advised to the valve cover off so you can listen to the valve gallery as if the gasket is blown at the gallery it is leaking air will be louder at it instead of the crankcase fill tube.
     
    The cylinder head torque was increased to 250 in lbs using three stage step torque, previously it was 220 in lbs.
     
     


    Thank you for the tips. I don’t have leak down tester and think that’s getting out of my skill set.

    From when I got the mower the was no square cut gasket between the intake and head, looks like a rubber o-ring set in the intake. Ill see about getting a new one and replacing that. In also going to up load a video here in a second for a better idea of what's happening.

    Thanks again!
    Mikel1
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    Re: Briggs and Stratton 311777 2018/06/28 11:17:07 (permalink)
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    Sounds like its running rich, you sure its oily and not carbon?
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