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Kohler 20hp sputting

Discussion in 'Mechanic and Repair' started by mcambrose, Dec 27, 2004.

  1. mcambrose

    mcambrose LawnSite Senior Member
    Messages: 514

    My Kohler 20hp (in a Walker) has about 1,600 hrs. It starts fine and seems to run fine when it is cold. After a while ( 20 minutes or so) the engine starts to sputter intermittently at full throttle and the rpms decrease. The sputter is similar to what you get when there is water in the fuel filter, but I have checked that several times and have also cleaned the carburetor bowl and didn't find any water. Could this be a blown head gasket. I had similar problem with a 25hp and it was a head gasket, but it had a sound that was like a sneeze when the engine was turned off and I don't hear that in this engine. Any help would be appreciated.
  2. Travis Followell

    Travis Followell LawnSite Silver Member
    from KY
    Messages: 2,206

    One thing that you could try that may or may not help is put some fuel treatment in it. Its probibly got a small amount of water in it so the fuel treatment should solve the problem if it does. Burn out that whole tank of gas before you put anymore in it. If it still does it with the next tankful then you may have a blown head gasket.
  3. fixer67

    fixer67 LawnSite Silver Member
    Messages: 2,098

    Are you sure it is firing on both cylinders when it gets warmed up? After a few minutes on one side the coil may be getting hot and mis-firing. I seen that before. Have you checked the spark plugs? If a plug gets fouled it can cause mis-firing after a few minutes of running. Also try removing the fuel cap, if the cap is not venting the engine will act fine on start up and then act up as a vacuum is pulled in the fuel tank because the tank vent is plugged. When was the last oil change and what weight oil was used? If the oil gets thinned out from being too old (too used) then the hydraulic lifters will act up when the engine heats up. And use 10W-30 only, if you use SAE 30 the hydraulic lifters will go nuts.
  4. mcambrose

    mcambrose LawnSite Senior Member
    Messages: 514

    Thanks for the suggestions. I will try what both of you suggested. All are very good suggestions. I use Mobil 1 sythetic 10w30 and it has probably been 15 hrs since oil change.

    UNISCAPER LawnSite Bronze Member
    Messages: 1,426

    They may have changed this, but there was a time when Kohler schools told us that synthetic oils should not ever be run in thier air cooled engines. The why part was never answered, but I thought I would pass this along....
  6. Mikes Machines

    Mikes Machines LawnSite Member
    Messages: 112

    If you suspect a head gasket which is not uncommon on Kohlers the check for it is a leakdown tester. If you do not have one most repair shops do. It shouldnt take more than 10 or 15 minutes. Some shops wont charge you too much for this other shops have a minimum charge. This would tell you for sure that the gasket is or isnt good. If you suspect fuel contamination a flashlight in the tank should give you a clue, also drain the carb to try to flush out any contamination. Also kohler do have some problems withthe coils
  7. mcambrose

    mcambrose LawnSite Senior Member
    Messages: 514

    I agree that the coil is a likely suspect. How can I test to see if the coil is the problem? If there is not a test, do I just have to replace the coil and see if it helps.
  8. Mikes Machines

    Mikes Machines LawnSite Member
    Messages: 112

    For a do it yourselfer there isnt an easy way to check them other than replacement. Kohler does have an electronic tester but even that is not foolproof. For a home type mechanic about all you could do is positively eliminate all causes other than the coils then if it still acts up replace the coils. You could also pay a Kohler dealer to test the coils for you. They need to be in the machine for testing. This is why I suggested a leak down test. I am not saying there is or is not a bad head gasket but this tells us for sure if we have a compression related problem or not. Then verify the fuel system, this means from fuel filler cap to intake manifold. Not just I changed the fuel filter. Another clue would be one plug being considerably darker than the other. There is only one carb so both plugs should burn the same as long as there arent compression problems or vacuum leaks. The coils will work until they get good and hot then fail but they can also fail cold. The amount of time before yours acts up could indicate a coil problem. It is just too hard to fix over the internet but I hope these suggestions help.
  9. mcambrose

    mcambrose LawnSite Senior Member
    Messages: 514

    I was finally able to get the mower to act up while at the mechanic. He used his tester to show me that one of the cylinder's wasn't firing. I had just replaced the plug about 10 hours before, but the plug was fouled. He replaced the plug with a new one and it worked great immediately. The plug may have been fouled by water in the gas line a few hours before. The mechanic said he had previously had problems with some Champion plugs fouling. Thanks for everyone's suggestions. I guess I don't underst and why the mower would work fine when cold and then act up after it heated up. I'm just thankful to have it fixed.
  10. Mikes Machines

    Mikes Machines LawnSite Member
    Messages: 112

    I dont want to jinx you or anything but I am still a little suspect of a problem. It is not normal to foul only one plug. This is what can happen when a coil starts to fail it also could point to a mechanical problem with that cylinder. I do hope that it was a fluke. If it truly was water in the fuel that fouled the plug it would have left tell tale signs on both plugs because both cylinders are pulling the same fuel from the same carb. Any way if it runs ok now good for you :drinkup: :drinkup: :drinkup: :drinkup:

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