Surging Engine

Discussion in 'Mechanic and Repair' started by wvaughn7, Aug 16, 2011.

  1. wvaughn7

    wvaughn7 LawnSite Member
    Messages: 219

    OK, we have a liquid cooled 27 HP Kawasaki engine model number FD750D-S04. It has a very bad surging problem from half throttle and above as long as it is not under a load. Once the blades are engaged or if you drive up a hill it smooths out and runs great. Another thing is it backfires and sputters when we take it from full throttle back to idle after it has been ran for a few minutes. Is there anything we should look at to try to sure these problems? The only things we have done so far are new fuel and air filters. Could it be an improperly adjusted governer? I really had no clue where to start.
  2. StanWilhite

    StanWilhite LawnSite Silver Member
    Messages: 2,397

    My 26hp LC Kawi came from the factory with the fuel mixture set extremely lean. If I pulled the throttle from wide open to idle it would die....every single time without fail. I reset the mixture and it straightened right out. Is your mower out of warranty?
  3. wvaughn7

    wvaughn7 LawnSite Member
    Messages: 219

    Yes it is very out of warranty haha around 5 years ago to be exact. It works great and other than these two things is in great condition. I was just wondering what everyone else thought I should start out trying. I am going to set the carb tomorrow night, I just don't exactly know how to do it without a tach. I have the service manual, but it states to set it at different RPM's while adjusting each part.
  4. StanWilhite

    StanWilhite LawnSite Silver Member
    Messages: 2,397

    Well, I thought if you had just bought the mower new, that maybe your problem was like mine was. But, since you've had the mower as long as you have, your problem is going to be something other than a mis-adjustment from the factory.
    Sorry, Stan
  5. wvaughn7

    wvaughn7 LawnSite Member
    Messages: 219

    Well the mower is relatively new to us, and it has done that since we got it so maybe it is the problem. Thanks for your help.
  6. gebby

    gebby LawnSite Senior Member
    Messages: 712

    I'd change the plugs, clean and adjust the carb, check and or replace the fuel lines, clean the sediment bowl, Change the fuel filter try a little top end cleaner (mix with your fuel). Replace the air cleaner. I also blow compressed air around the carb and in it. Be careful when doing. It could be anything fuel related. My 15 hp Kaw will do that. I do the above and one of those things usually does the trick. If all else fails don't be afraid to take to the dealer. Usually money well spent.
  7. Merkava_4

    Merkava_4 LawnSite Bronze Member
    Messages: 1,443

    You have an obstruction in your idle circuit. As soon as you put the engine under
    load, the engine no longer runs off the idle circuit - it runs off the main nozzle.

    Either that or you need to dial in your idle mixture.

    Last edited: Aug 17, 2011
  8. wvaughn7

    wvaughn7 LawnSite Member
    Messages: 219

    Merkava that is a much moer useful response. I worked late today and didn't get a chance to work on it, but I will start there as I have already performed all the things gebby suggested except for cleaning the carb. Hopefully that will solve our problem.
  9. Ridin' Green

    Ridin' Green LawnSite Fanatic
    Male, from Michigan
    Messages: 17,828

    This is the answer you needed. The low speed circuit is plugged (at least partially). I just went through this with an old JD push mower that I picked up cheap, but that was still in good shape.

    I first removed the float bowl, and found lots of "debris/sediment" in there. I cleaned it, then blasted Gumout carb cleaner all around the outside of the carb, and ran some through the throat of the carb while the engine was running. I still couldn't get it to clear so I took the thing apart as far as was possible, and really cleaned it up with the Gumout spray, and a soaking. When I put it back together and fired it up, it was still surging, but after about 20-30 seconds it coughed a little, sputtered then smoothed right on out. I have run a few tanks of Sea Foam through it since to get any remaining varnish. That stuff works pretty well.:)

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