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sticky valves? kohler CH740

Discussion in 'Mechanic and Repair' started by cgrand, May 26, 2009.

  1. cgrand

    cgrand LawnSite Member
    Posts: 15


    hope everyone had a nice holiday

    the 27HP kohler on my turf tiger keeps bending the push rods under the same set of rocker arms...one on each side of the block, at the valve closest to the rear of the mower

    this has happened twice now, about 20 hrs apart. engine has 1700+ hours, i bought it used and do not know the maintenance history

    i assume this is a case of sticky valves due to carbon build-up? if so, how do i de-carbon (seafoam?)?

    any other thoughts?
  2. ricky86

    ricky86 LawnSite Bronze Member
    Posts: 1,841

    It could be. It could be the lifters also. Or both. I would try a valve train kit and new lifters first. A whole lot easier. You can take the lifters apart for cleaning, but they are only about 20.00 each. The valve train kit is rockers, pivots and push rods. One kit, one side. (If I remember correctly)
  3. cgrand

    cgrand LawnSite Member
    Posts: 15

    is a visual inspection enough to determine what my issue is? as far as i have gotten is removing the valve covers and replacing the push rods. the rockers appear to be fine...what else am i looking for?
  4. ricky86

    ricky86 LawnSite Bronze Member
    Posts: 1,841

    You should be able to push the valves down by hand. Not the lifter, but the valves. Are you using 10W-30 oil? I would at least replace one lifter in one side and see if the problem goes away in that side. I have never seen valves sticking in a CH25, but it is possible I guess. Engine would backfire when the valve sticks, but it will do the same thing when the pushrod bends. When a unit comes into the shop with a bent push rod, the lifter is removed and inspected and usually replaced (because they always look ok) along with making sure the oil supply hole in the block is clear. It is not a good idea to switch lifters from side to side and never use a used one (just in case you were thinking of doing that ).
  5. cgrand

    cgrand LawnSite Member
    Posts: 15

    here's what the local scag dealer told me...

    he said kohler has advised them that older engines (mine is definitely older) are having backfire issues with ethanol-blended fuel (and yes, mine was backfiring at shut down), which could bend the rods, and that i should shut it down at full throttle, instead of idling it down first

    so last night i changed both of the bent push rods, put it back together, and mowed a little grass, ran fine. at shut down i did as advised and it didn't backfire.

    i am using 10w30
    the next time i open it up the check the rods i'll have a look at the lifters

  6. ricky86

    ricky86 LawnSite Bronze Member
    Posts: 1,841

    Thats nothing new. You should always shut down at 2/3 to full because of the fuel solenoid. You should idle it a while to cool the engine before whacking it to WOT. The part about the Kohler advisory is interesting. I wonder how they advised them? We are a expert dealer and haven't heard anything like that. Maybe that dealer is special. Personally, I think your dealer is FOS, but I hope you can find a solution to your problem. I can't for the life of me understand how a backfire can bend the same pushrod on both #1 and #2 cylinders. They are at different points of their cycle.

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