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Kohler CH25s problems

Discussion in 'Mechanic and Repair' started by 2dedge, Oct 23, 2007.

  1. 2dedge

    2dedge LawnSite Member
    Messages: 4

    I have a ch25s with 1420 hrs it was running pretty well at idle but as soon as you throttle up and put a load on it it starts to make a popping/sucking sound that seems to only be on one bank. Did a compression test and both cyl were 180, plugs look a little lean whitish, and when you run it with out the air cleaner it seems to spray fuel back through the carb.

    So I read all the posts I could find here and talked to the local shop and the general concencious was bad head gaskets and an intake leak.

    Replaced the head gaskets, one of which was smoked. Replaced the intake and exhaust gaskets cause they come with the kit. Reassemble and it runs the same:hammerhead: So I run it some more with the valve covers off thinking may be I have a bent push rod or collapsed lift but every thing looks ok. Basically its running like a chevy motor with a worn out cam.

    Family SK#725u1g2ra
    Model ch25s
    Spec 68590
    displacement 725
    S# 2916618831

  2. stevesmowing

    stevesmowing LawnSite Senior Member
    Messages: 847

    did you check the spacing between the lifters and the valve stems? If it is overhead cam which it sounds like it is, they may need adjusting.
  3. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    I have seen baffles break loose inside the muffler and restrict exhaust flow, They would make strange muffled noises/pop and spit fuel back out of the carb and lack power.

    Just something to check......
  4. pugs

    pugs LawnSite Gold Member
    Messages: 3,024

    Leakdown test? How did the valves look? If you went through the trouble to take the heads off I would have at least cleaned/lapped the vavles if not done a complete valve job while you were in there...
  5. 2dedge

    2dedge LawnSite Member
    Messages: 4

    One of the local shops suggested the coils may be bad also:dizzy:
  6. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Well, It's possible there is a problem with the SAM.

    Enter your engine numbers in the link below and down-load a service manual, Go to section 8 and check the ignition system. But, There is a special tester required to fully test the SAM but you can get a basic idea.

  7. 2dedge

    2dedge LawnSite Member
    Messages: 4

    Well after all was said and done I found my problem today.

    Bad cam shaft:hammerhead: One of the lifters was scared and the cam was almost flat on that lobe.

    Note to self next time pull both valve covers at the same time and crank over with plugs disconnected and watch the lift on all 4 rockers.

    Bought a new motor and installed it myself to the tune of 1800 bucks
  8. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Hmmm, The above statement removed any thought to a worn cam lobe !

    Will you be replacing the cam and lifters in this engine to have a back-up on the shelf ?
  9. 2dedge

    2dedge LawnSite Member
    Messages: 4

    We might what is involed getting to the cam?
  10. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Flip the engine up side down and remove the sump (oil pan), It will be sitting there looking at you.

    If you go to the link I posted and down-load the manual it will tell you all you need to know for this job.

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