Small engine?

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FTGV
FTGV Posts: 3,649
edited May 2010 in The Clubhouse
My lawn mower has a Briggs & Stratton that is acting up.It starts great but after about 15 min it starts to lose power, sputter and gets very hot,acting like its about to cease.Any ideas?
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  • Jstas
    Jstas Posts: 14,712
    edited May 2010
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    Is it out of oil?
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  • FTGV
    FTGV Posts: 3,649
    edited May 2010
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    Nope she's full.
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  • Jstas
    Jstas Posts: 14,712
    edited May 2010
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    Have you checked the plug?

    Also, when was the last time you cleaned the air filter?
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  • FTGV
    FTGV Posts: 3,649
    edited May 2010
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    Jstas wrote: »
    Have you checked the plug?
    It looked OK ,but didnt check gapping,not sure what it should be.
    Also, when was the last time you cleaned the air filter?
    Can't remember.:D
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  • billbillw
    billbillw Posts: 6,185
    edited May 2010
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    Sounds like she is running rich. Dirty filter or perhaps a float sticking?
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  • MillerLiteScott
    MillerLiteScott Posts: 2,561
    edited May 2010
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    Take the cooling shroud off and clean out the cooling fins @ the cylinder and cylinder head. It may be full of debris not letting the fan on top cool the cylinder. Also check the fan to make sure it is not clogged.

    Scott
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  • Echosphere
    Echosphere Posts: 395
    edited May 2010
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    How old is the gas in there?
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  • disneyjoe7
    disneyjoe7 Posts: 11,435
    edited May 2010
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    I don't like the fact it hot and loosing power, but it has oil. Can you change the oil?

    Or is she lean, but why a dirty air filter would cause it to be rich...:confused:

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  • ohskigod
    ohskigod Posts: 6,501
    edited May 2010
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    It's getting hot for some reason, though I have no idea why it is. I would say check the cooling system if it had one, which it don't. check the oil quality, is it sludgey?

    maybe clean the engine? it is aircooled so if it is dirty (oily or yard smutz....or both) try giving it a nice clean.

    change the plug can't hurt either
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  • Jstas
    Jstas Posts: 14,712
    edited May 2010
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    disneyjoe7 wrote: »
    but why a dirty air filter would cause it to be rich...:confused:

    Ummm....really?

    Rich condition is a ton of fuel and not enough air to burn the fuel completely.

    A clogged air filter reduces the flow of air.

    Reducing the flow of air starves the engine for air but the carb still dumps fuel because it's flow is determined by the draw of the piston, not the air flow. So it sucks fuel like a fat kid eating pixie sticks.

    Too much fuel can cause carbon to build up in cylinder. Also, too much fuel can cause fuel to pool and smolder which brings up the temps in the combustion chamber. Also, liquid fuel cannot be compressed because fluids cannot be compressed. So as the fuel and soot build up it can change the compression ration enough that the timing and spark temperature are no longer hot enough to ignite the fuel/air mixture.

    You also get a condition happening where the electrical spark is snuffed out by the excess fuel in the chamber. Just like shooting a match with a water gun it's snuff it out.

    Also, you can reach a point where there is too much fuel in relation to air where there is not enough air for the fuel to ignite.

    All of this can cause the conditions the OP is having.
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  • superjunior
    superjunior Posts: 1,632
    edited May 2010
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    maybe a sticky choke. if its running fine for the first 15 min. than heating up and sputtering out,I would take a look to see if the choke is sticking. just a thought...
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  • Jstas
    Jstas Posts: 14,712
    edited May 2010
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    FTGV, do a tune up and clean the mower.

    First off, unplug the electrical connector to the spark plug so it doesn't accidentally start on you and lop something important off.

    Pull the plug and read the part number on the side of the ceramic insulator, go to a car parts store or a hardware store and get a new one. If you can, get a new filter element for the air filter. If you can't find one and you have a foam brick for a filter, you can clean it, I'll tell you how to do that below.

    While you are at the store, get yourself a quart of SAE straight 30 wt oil and a can of degreaser like Gunk Engine Brite or something and a scrub brush. Also, hand cleaner and gas stabilizer.

    When you get home, squirt that engine down with the degreaser and scrub it clean. Remove any plastic fairings it might have first. Once you have gotten the gunk scrubbed, hose it off and let it dry in the sun.

    Grab a spark plug socket or a wrench that works and put the new plug in the engine. Pull the filter for the air intake. If you got a new one, shove it in there and button it back up. If not, grab a metal coffee can or large glass jar and pour some gasoline in it. Drop the filter in and let it soak up the gas. Squeeze it out and keep doing it until it's clean. Once it's clean wring it out very well and let it sit in the sun while you go take that hand cleaner and clean the gasoline off your hands. If you want to use gloves for that, use nitrile gloves. Rubber gloves will melt to your hand.

    Once the filter is dry, install it. Next, get a drain pan and a couple of saw horses. Or at least something you can get the mower up in the air with and be able to access the oil drain plug. Undo the plug and drain the oil. Once it's all out, replace the plug and fill it up to the fill mark and close the fill plug.

    Put the electrical wire back on the plug. Measure the fuel stabilizer out to directions according to the label. Dump it in the tank and then fill the rest with good gas.

    Put the mower on the ground, get it set up to start and yank you're little heart out until it starts. Let it run for a bit and see if it dies again. If it does, your engine is trashed and you need a new one. If it doesn't and runs fine after all that, take better care of your mower, man.

    One other thing. If the mower runs fine now, let it run a bit and get all that funk out. It'll burn it off as it heats up to an appropriate level. You might notice some smoking. A little blue smoke from oil can be expected from the jostling but if it's alot, you got a bigger problem. If it's gray smoke, that's the funk burning off. If it doesn't stop with the gray smoking, you might have to get the carb rebuilt.
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  • FTGV
    FTGV Posts: 3,649
    edited May 2010
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    Thanks guys lots of things to check now.I did notice that there appears to be a short plastic hose missing that goes from the carb to what appears to be the crankcase?The mower was given to me a few years ago and has'nt had much use.But my 25yr old LawnBoy bit the dust so would like to get this one working.
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  • FTGV
    FTGV Posts: 3,649
    edited May 2010
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    Jstas wrote: »
    . So it sucks fuel like a fat kid eating pixie sticks.
    thats a good one:D.Thanks for the replies.
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  • mhmacw
    mhmacw Posts: 832
    edited May 2010
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    coil.....temperature related swell in the coil will seperate a broken wire after it heats up.
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  • jerryj12
    jerryj12 Posts: 451
    edited May 2010
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    FTGV wrote: »
    I did notice that there appears to be a short plastic hose missing that goes from the carb to what appears to be the crankcase?

    This hose acts as a pressure relief for the crank case.Like a PCV valve on most cars. Should be able to pick it up at the local small engine shop.
    mhmacw wrote: »
    coil.....temperature related swell in the coil will seperate a broken wire after it heats up.

    I would have to agree. Sounds like a good place to start.

    I would also get the old gas out of it,and pull the bowl off the carb and give it a good cleaning. A new plug would be a must.

    Good luck.
    Jerry
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  • FTGV
    FTGV Posts: 3,649
    edited May 2010
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    jerryj12 wrote: »
    This hose acts as a pressure relief for the crank case.Like a PCV valve on most cars. Should be able to pick it up at the local small engine shop.
    OK thanks Jerry,so it's not likely to be related to the problem?
    I would have to agree. Sounds like a good place to start.
    Could a problematic coil cause the overheating?
    I would also get the old gas out of it,and pull the bowl off the carb and give it a good cleaning. A new plug would be a must.
    For starters I will install a new plug and get an air filter and see what that does.There was a bit of very old gas but I filled it with new.
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  • jerryj12
    jerryj12 Posts: 451
    edited May 2010
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    Hey GV, any luck on the lawn mower?
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  • disneyjoe7
    disneyjoe7 Posts: 11,435
    edited May 2010
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    Heck the small engine is in your chest. Good luck, nice to see you on PF :)

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    WMC Win7 32bit HD DVR


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