Briggs & Stratton Black Smoke Gas Smell

boknows_2006July 29, 2006


I have a Yard Machines, Briggs & Stratton model 10A902 push mower. I was mowing and hit something causing the screw which connects the gas can, filter and primer section come unscrewed and fall to the side. I lifted the section back up and screwed it back in, but now the mower does not work. It sputters when I start it with the blade rotating until it touches grass and black smoke is coming from the muffler. Also there is a strong gas smell. I just replaced the filter, oil, gas, spark plug and used fuel systems cleaner. What do I do? I am in the military away from home and cannot afford a new mower. Please help if you can. Thank you,


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You may have sheared the flywheel key when you hit something, and this has altered the timing,causing rough running.
Also make sure there is no engine oil gone into the air filter,causing the engine to blow black smoke (this happens if you tilt the mower the wrong way)

    Bookmark   July 30, 2006 at 7:41AM
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How do I fix the flywheel key? Also I replaced the filter so there shouldn't be any oil in there.

Today I tried to start it and it would only go for about 10 seconds and it sputtered the whole time. Also a strong gas smell is present.


    Bookmark   July 30, 2006 at 12:41PM
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Need a little more info on this. Did you hit something with the mower's blade, or did you hit the side of the mower against a fence or something? What is the model of the b&s engine? Sounds like the engine is running with a rich mixture, is there a chock on this that may be stuck closed? Can you see leaking gas, or is just the smell?

    Bookmark   July 30, 2006 at 3:43PM
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Weed cutter,

The model number is 10A902. I didn't run something over, I actually hit up against a fench. It wasn't too hard but enough to knock the screw loose that holds the gas tank, filter and primer section off. I thought that all I needed to do was line up the tubes and screw it back in, but it hasn't worked since. I am not sure about the choke, I know that the throttle is preset so I cannot speed it up or slow it down. I don't think I can adjust the choke? Under the front of the motor where the spark plug connects it was wet from some gas and smelled of gas odor. I don't want to take it down to have it fixed if it is going to cost too much, but I don't much about fixing engines so I don't know what it is supposed to look like. Thanks for the help!


    Bookmark   July 30, 2006 at 7:05PM
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Still meed the model # of theENGINE. You might try the MTD Yard Machines web site, but I think you'll have better luck with the B&S model # at the B&S site. I'n not doubting you a bit but I can't visualize what your problem is. I've always seen 2 bolts holding this stuff on the side of the engine.


    Bookmark   July 30, 2006 at 9:50PM
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You're spinning yer wheels! bite the bullet and take it to a repair shop, and have them look at it, and they will advise you on how much it will cost to repair it. By the time we all figure out just what you're trying to tell us, ye grass will be up to yer ears, and it still won't run!

    Bookmark   July 31, 2006 at 1:53PM
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If the tank pulled away from the casing, and you are having a strong gas smell, sounds like the gaskets between the tank and case is lost. Should be a black "O" ring on the inner portion located on the tank side and a ceramic seal on top of that.

    Bookmark   August 26, 2006 at 4:10PM
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Also, check that little tab that the governor spring is attached to and see if it got bent. I had that problem and it made my mower (a Yardmachines also) run really rough because of the governor being off. I replaced the diaphragm and bent that tab back and it was working until today when I came up with another problem.

    Bookmark   October 10, 2006 at 4:39PM
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