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  1. #1

    Default Kohler Knocking

    Hello, everyone. Hopefully I can get some advice here. I rebuilt a Kohler K241 10hp a couple of months ago; new piston, rings, rod, and valves. The cylinder was dingle-balled, it was not out-of-round or scratched up, and the crank checked out OK also. The piston and rod that I bought are the original size. The valve seats were ground. Everything was lubed very well when it was put together. I had some help from a friend who has rebuilt a few of them, and he also did the work on the valve seats and bore (him and his father have a complete machine shop.)

    I did make one mistake when putting it together, the breaker cam was put in 180 degrees out, so it did have to be torn back down to correct this (crank and piston came back out). The connecting rod I bought had the posi-lock nuts on it, and these were tightened to 200 in-lbs the second time it was installed.

    It had run fine until yesterday. I ran it for about an hour after the rebuild, driving it around the street and yard to get some time on it, varying the rpm's, and then changed the oil. Since then, I've got about 10 hours on it, doing some light snow plowing, all in low gear. Last night, it started knocking real good, and sounds like I might be where I was before the rebuild.

    My questions are: What could be a cause of this? Do you think the rod was put together incorrectly? I've heard some say you shouldn't re-use the posi-lock nuts. Should I get the crank turned, and buy an undersize rod? As I said, the machine work would not cost anything, it's all available.

    Thanks for any help!

    Jeff


  2. #2
    Elite Member
    Join Date
    Mar 2002
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    3,385

    Default Re: Kohler Knocking

    It sounds like you might have "piston slap", (bottom of piston hitting cyl. wall). Not sure what "cylinder was dingle-balled" means, but was there any ring groove at the top, cyl. diameter still within specs., ring clearance within specs? Did you have to, or should you have honed the cylinder and gone oversize on piston and/or rings?

  3. #3
    Elite Member thcri's Avatar
    Join Date
    Jan 2003
    Posts
    4,645
    Location
    Minnesota SE
    Tractor
    New Holland TC29D, 2001

    Default Re: Kohler Knocking

    My last suburban had piston slap. It was a 98 and General Motors would not do anything with it. Under warranty they told me piston slap would not hurt a motor and all motors have it some. I was not impressed but did learn to live with it. I sold the suburban when it had 85,000 miles. When you rebuilt the motor, what did you use to lubricate the crankshaft and rods while you put the motor back together. My dad was a mechanic for over 25 years on Ford tractors. He saw a guy using I think STP. Dad pretty much yelled at the guy because STP was so thick it stopped all oil flow until the crank heated it up enough to get it flowing. Not so sure if that is true, but dad sure stuck to his theory. I guess it makes sense.

    Murph

  4. #4
    Veteran Member
    Join Date
    Dec 2002
    Posts
    1,070
    Location
    Western Washington
    Tractor
    5300 JD 4X4

    Default Re: Kohler Knocking

    Take a stethescope and listen to the block as you turn the crank pulley be hand, if you hear a clunk clunk when you rock the crank back and forth it is most likely the rod.
    This might be far out, but I have known it to happen. Check the intake for missing screws on the butterfly in the carb. If one of those gets in the cylinder it beats on the piston like a drum, sounds like a rod is going to go.
    I once had a rod bolt break at the shank. It let the piston slap the head, but didn't break, sounded like a loud lifter. Had to tear it down completely to find the culprit.
    That was a 336 Yanmar with 300hrs on it.

  5. #5

    Join Date
    Nov 2002
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    112
    Location
    Harbor Springs Michigan
    Tractor
    Bx2200

    Default Re: Kohler Knocking

    unfortunely you only have one option. take it out and take it apart. It won't get better, anyone of these posts could be right but taking it apart is the only way to find out, I vote for a loose con rod. [img]/forums/images/graemlins/frown.gif[/img]

  6. #6

    Default Re: Kohler Knocking

    Thanks for the ideas. I was wondering if it might be piston slap, or the loose rod. It's a sharp knock, not a dull thud, and you can hear it even when the engine is turning over from the starter. I didn't think about loose screws getting sucked in, I'll check for that. By "dingle-balled", I meant we honed the cylinder with the style of hone that has the little balls at the end of the wires, getting a good sideways marking in the cylinder so the rings would set. The cylinder was still within spec, no grooves in it at the top or anything, and it's not been bored over yet. We squirted 5W-30 over everything inside (cam, rod, crank, bearing), lubed up the piston and dumped about a teaspoon of oil on top of it when we put it together.

    I had kinda resigned myself to taking it apart to find out what it looks like. It's just a pain doing all that work! Lol. If I do need to replace the rod, do you think the bearing for the crankshaft should also get replaced? Also, does anyone know the specs for the diameter of the crank at the rod?

    Thanks!

    Jeff

  7. #7
    Platinum Member Molerj's Avatar
    Join Date
    Jul 2001
    Posts
    572
    Location
    Eastern Ohio
    Tractor
    JD 955, Economy Power King

    Default Re: Kohler Knocking

    I vote for a loose connecting rod bolt. Don't you just hate it when you have to tear something all apart again? Only good thing is you can do it alot faster the second or third time! Go to the site below, select parts lookup>kohler>k series>specs. Hope this helps. try here

  8. #8

    Join Date
    Feb 2002
    Posts
    540
    Location
    Mukwonago, WI
    Tractor
    BX2200, '52 8N

    Default Re: Kohler Knocking

    Well you should have used a new rod bearing from the start. You should have measured the crank journal for size to see if had any significant wear. The next step is then to measure the rod big end size with the bearing in place and the rod bolts toqued to spec to get the clearance. Or you could have used plastigauge to determine the rod to crank clearance. This would have told you if the crank needed to be ground or polished and if you needed an oversize rod bearing. You should also check the side clearance of the rod and crank. And of course after you tear it down again look for loose rod bolts. Good luck!

  9. #9
    Elite Member
    Join Date
    Mar 2002
    Posts
    3,385

    Default Re: Kohler Knocking

    Jeff, considering the inspection and work you did on the cylinder walls, the fact that it ran well for 10 hours, and you can hear it at slow cranking, I'm moving away from my "piston slap" diagnosis, to "something came loose", something fell in it, or something didn't get oil. In any case, it should show up quickly with a teardown.

  10. #10
    Gold Member
    Join Date
    Jul 2002
    Posts
    289
    Location
    ECNY
    Tractor
    DK35

    Default Re: Kohler Knocking


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