What causes a push rod to bend?

Discussion in 'Mechanic and Repair' started by ealbertson, Aug 6, 2006.

  1. ealbertson

    ealbertson LawnSite Senior Member
    Messages: 256

    I have 26hp EFI Kohler engine with the left bank's exhaust push rod bent. First, what typically causes this and second will that cause the plug to foul out every few hours?
    The valve pushes in as easily as the intake valve.

    Thanks, ED
  2. dutch1

    dutch1 LawnSite Silver Member
    from Jayhawk
    Messages: 2,249

    It's possible that you have an exhaust valve that is partially sticking thereby putting undue stress on the pushrod. It's likely that fouling of the plug on that bank could be a result incomplete combustion on that side due to the sticky valve. Removal of the head will likely reveal your problem. A bad valve oil seal, carbon buildup, leaky head gasket or rings/piston wear could contribute to the problem.

    A commercial landscaper breought me two wheel blowers that they had been burning 2 cycle fuel in because their crews couldn't keep the two fuel situation straight. Both had stuck exhaust valves due to carbon buildup on the stem.

  3. viper00085

    viper00085 LawnSite Member
    from NC/VA
    Messages: 237

    valves sticking are a good bet as mentioned above. also make sure the valve guide has not moved its way out, usually this is the culprit from overheating, the alum head will expand more than the guide and allow it slide out and not allow the valve to open all the way and bind/bend the push rods. also kohler is bad for rockers coming loose from bad /stripped threads in the head, check that out as well.
  4. ealbertson

    ealbertson LawnSite Senior Member
    Messages: 256

    Hey guys thanks for the input one other question and then some feed back on what I found. First, there was no valve stem seal on the exhaust. The lady at the parts shop said it doesn't show a stem seal for the ex. side. Also, there was none on it. At first I assumed it burned off. Do you guys know if it doesn't take an ex. seal? The second thing is the ex. valve was burned although it did feel free in the guide. At that time I didn't know to check if the guide had moved in the head. Is it hard to see if it has moved?

    Thanks again, Ed
  5. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    There is no seal on the exhaust valve, All you have to do is look in the exhaust port and see if you can see about 1/8" of the guide protruding into the port area. But I would remove the valve spring and check the guide and buff the valve stem re-lube with oil then re-install.
  6. ealbertson

    ealbertson LawnSite Senior Member
    Messages: 256

    Is 1/8th inch what I want to see or does that mean there is a problem?

    Thanks again, Ed
  7. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Sorry :hammerhead: Thats what you want to see, I really doubt the guide moved I am yet to see one that has.
  8. tomo

    tomo LawnSite Senior Member
    Messages: 660

    Hello, sloppy valve train also, look 4 more than a minor wear pattern on the lifter base, inspect cam for wear either by eye or measure against new. Valve train does not have to be noisey for this to happen just excessive wear .Typical in many OEM OHV. As people have mentioned maybe sticky valve?? Oil consumption ,check eng condition comp test wet/dry ,leak down test,oil pressure check.HRS????? Make decision on engine with pro's advice. Info on engine oil consumption in kohlers is readily available if you do a search {air coolled command v twins all very similar] tomo
  9. JJ Lawn

    JJ Lawn LawnSite Senior Member
    Messages: 350

    There were three Kohler 26hp EFI engines in my area that did same, bent push rod. Two of them, mine included was caused by the rocker arm bolt backing off.
    The third I am not sure. But all three motors only had about 1200 hours on them.

    Neither Kohler or Walker say's there is a problem with this.

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