Riding Mower engine going chugga chugga chugga

Discussion in 'Shop Talk' started by mary,tx, Sep 10, 2004.

  1. mary,tx

    mary,tx Well-Known Member Supporter

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    I have a Husky riding lawnmower that has been fairly reliable over the years. I had been out of town and DW was mowing out back and she reported that the mower was smoking oil. In the past it turned out to be a just a stick stuck in the drive belt or something like that. When I started it there was no smoke but it ran very rough.

    I brought the mower to the car port. I cleaned out the air filter, changed the plugs, changed the fuel filter, and cleared everything from the belts. I added oil to the engine (our son was supposed to check the level, but it was still quite low.) The engine still runs rough and at times will give off a lot of black smoke, but it appears that it is either lack of air or lack of fuel (idling too slow). The tall (green) grass near the exhaust appears to be blackened from soot when it had a smoking spell. I can turn off the engine for awhile and it will run without the smoke but will still be rough. (When in smoke mode, the engine is about to die.) The plugs were not fouled but were dark but not oily, so I do not think it is burning oil.

    There is not much power to run the mower, but I can pull a small load slowly. The throttle is fully open and operates properly and the choke cable and linkage also work properly. The engine is a two cylinder B&S.

    Any ideas of what to try? Would getting a carb kit be worthwhile? I do not want to do any adjustments on the carb since everything was working fine before and it appears that none of the screw settings have been upset.

    Thanks,
    Dale (DH of mary, tx)
     
  2. Beeman

    Beeman Well-Known Member

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    Total guess on my part. Is it black smoke like too much fuel? If it is black smoke try this: First does the engine have a fuel shutoff valve in line from the tank to the carb? If it does shut the fuel off after you start the engine and see what happens. The engine should continue to run on the fuel that is in the float bowl. If the engine clears out and runs better until it uses all of the fuel in the bowl you probably have a leaky needle valve in the float bowl or a porous float that is allowing too much fuel in. If this makes the engine run better do it a couple of times, some times the incoming rush of fuel into an empty bowl will flush out the debris from the needle valve. If it ran better but repeating the procedure did nothing than remove the carb or the float bowl and inspect for your problem. If your fuel line doesn't have a shutoff valve but has a rubber line just pinch off the line with pliers or a visegrip.
    Like I said it's only a guess.

    Another thing to try is adjusting the carb but always turn the screws IN first and note the number of turns to reach bottom so you can put them back to original setting if no improvement. Turn them in slowly and bottom them gently. Also try opening adjustment screw slowly past the initial setting with the engine running, sometimes this will help clean out any blockage.
     

  3. Blu3duk

    Blu3duk Well-Known Member

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    Ive got a b & S vangaurd twin 14 horse, and it did the same tyhing a couple years back, new fuel pump [some of the twins have a $5.00 rebuildable] for $35.00 which is kinda spendy, but it beats a new engine for $650 plus shipping, or a new mower for nearly 3 times that. the other thing to check is the fuel lines themself, they get hard and cracked or let air pass by and the engine gets starved for fuel on those twins, and they look like they are smoking and have no power.

    it could be something else too, but i would check that fuel pump.

    William
     
  4. ohio_kid

    ohio_kid Well-Known Member

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    This is also a guess, but I'm wondering if the valves are not seating properly. If the valves are not seating then the fuel isn't being completely burnt. I'd take it to a trustworthy shop and have it looked at.
     
  5. Ross

    Ross Moderator Staff Member Supporter

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    Sudden changes allways make me think of timing or bad gas but I'm not familiar with the engine and I'm no expert.
     
  6. mary,tx

    mary,tx Well-Known Member Supporter

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    Alright, this is the update in trying to figure out the problem with my engine going chugga chugga. (I am no engine expert).

    I checked the position of the screw on the carb tightening all the way and then backed it off an extra turn and then set to the original position. No change. Changing the position of the screw while the engine was running made little difference, so it was put back at the original setting.

    I could not pinch the gas line hose, but took the hose off the engine (holding the end up to not spill gas). I started the engine and still chugga chugga of course, but after awhile, the engine ran fine for a moment until it died as the fuel was used up. Putting the hose back on, the engine ran fine for awhile but then reverted to chugga chugga.

    I took the rectangular cover of the thingy on the front of the engine where the fuel hose is connected (taking the hose off first and letting the engine run until it used up the fuel). I didn't know what I was looking at, but everything looked clean inside. Put the cover and hose back on and the engine ran great for a short while, then back to the smoky chugga chugga chugga. I think I am on to something, but I don't know what. Inside the thingy there was a very small weak spring pushing a flap of rubber forward. What is this? How do I check the float valve? Should I buy a new innards for the thingy? (BTW, what is this called?)

    What should I do next?

    Thanks,
    Dale (DH of mary, tx)
     
  7. fordy

    fordy Well-Known Member

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    .............................................The carb could be malfunctioning. The float could be shutting off before it allows the bowl to fill fill completely thereby preventing the engine from receiving the proper amount of fuel necessary . But, that wouldn't explain the smoking . ...fordy... :eek: :)
     
  8. Beeman

    Beeman Well-Known Member

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    Okay,
    The part you removed to look at is just the crankcase vent. The fact that the engine ran good with the fuel line off(which is a little on the dangerous side if fuel spills) leads me to believe you have a porous float or dirt in the needle and seat section of the carb.
    I have absolutely no way of knowing your ability so all I can say is use your best judgement on how far you should go. Be sure the engine is cold and there is nothing that will ignite gas around.
    The carb should have a round bowl looking part on the bottom. At the bottom of that is usually a fitting which sometimes has an adjustment screw in it. If you have this setup you can go from here. FIRST, pinch off or disconnect the fuel line. Then remove the fitting at the bottom of the bowl which should have a hex head you use a wrench on. Pay attention to the position of the bowl as some have an indent that must be positioned correctly. Once the fitting is removed(if it has an adjustment screw in it just remove it with the screw in it) The bowl will come off as it seals with an O-ring. You will now be looking at the float which is the round part that "floats" up and down in the gasoline. And the part the float attaches to which is the needle and seat assy. This works just like the tank on your toilet at home. As the fuel level drops in the carb the float drops opening the needle and allowing more gas to enter the bowl. When it reaches the proper level it closes the needle and shuts off the fuel flow. Now you can check this by rehooking the fuel line and working the float up and down gently to see if it shuts off the fuel. I stress gently because the float is set at a certain height and pushing upward too hard will bend the adjustment tab and definetly cause a problem. If when the float is raised to the height where it should close the needle and fuel still flows you probably have dirt in the needle and seat or a worn needle. If the fuel shuts off you might have a porous float or another problem all together. Whether or not the fuel shuts off if you want to proceed furthur you will have to remove the float. The float itself is usually retained by a pin that it pivots on. The pin is just a slide in fit and is held by the fact it cannot slide out with the bowl on the carb. Pay very close attention to how everything is assembled BEFORE you pull the pin out. Holding everything in place with one hand, remove the pin. You will now have the float and the needle in your hand. If you suspect the needle because the fuel wouldn't shut off look carefully at it and the seat part which is still in the carb. The seat will be brass usually and hex shaped and will unscrew from the carb body. You can try cleaning them or if you buy a rebuild kit they will come in it. If that is your problem be sure to also replace your fuel filter or if you don't have one now is a good time to install one.Now the float can be either brass or a plastic material. If the float is brass it should be light as it is hollow. Shake the float and it shouldn't have anything in it. If there is gas inside the hollow float that is your problem and the float needs replacing. If the float is plastic sometimes they are hollow like the brass one and sometimes they are like a piece of styrofoam. If it is solid it should be light and should float on top of a container of water or gas. If it sinks or is heavy it is no good. If the float needs replacement it will also need to be adjusted. The float level is usually that the needle will be closed when the float is parallell to the flat part of the carb where the bowl seals.
    I hope some of this helps you but please be careful! Gasoline can ignite easily or can also cause skin problems when contacted. Be careful of the fumes also.
     
  9. moopups

    moopups In Remembrance

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    Ok, when its chugging, is there very black smoke comming from the muffler? If yes its getting too much fuel. If the smoke is blue it is burning oil. White smoke indicates water in the fuel.

    From your description of the problem there may be a quick fix. Do not adjust the carb, that is a pro's job. I suspect you have either a clogged atrosphere vent in the float bowl or a clogged jet. Take off the air cleaner, get the engine running as fast as it will run with no load, slap your palm over the air cleaner hole and stall the engine until it has maybe 2 or so strokes left before it stalls. Pull away your hand before it stalls, the suddon vacuum change may clear the obstruction. If this and whats to follow does not help, disassemble the carb and find the vent in the bowl that lets air in and out, if it is clogged the fuel will keep entering at a rate too much for the engine to consume.

    I am assumeing you have a crisp blue spark? If yes thats good, but do check it at night when you can see any other sparks. The electrical system may be causeing the chugging.

    The atrosphere vent is tiny, smaller than a pencil lead in diameter, use wd 40 or similar to see positively that it is open. The last place to look is the choke flapper (butterfly), it could be with a broken shaft or similar that is not visable until you disassemble. The vent will be located in the top of the float houseing chamber.
     
  10. herefordman

    herefordman Well-Known Member

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    At the risk of sounding too simplified here, you said in your first letter the "son" was supposed to have topped up the oil but the level was still low, you sure he didn't put the oil in the gas tank by mistake ?..........kids are so much fun :)