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Power Drop on Kohler 18hp

Discussion in 'Mechanic and Repair' started by clean_cut, Feb 27, 2011.

  1. clean_cut

    clean_cut LawnSite Bronze Member
    Messages: 1,327

    I have a scag wb with the Kohler engine found here...

    http://www.kohlerengines.com/onlinecatalog/productDetail.htm?productNumber=Command PRO CV493

    I recently put a new silicone seal on the valve cover to fix an oil leak. Since then, the engine seems to have lost power. If I open up the throttle, it will take longer than usual for the engine to get to full throttle, it also takes the engine longer than normal to recover from me putting the throttle past full and onto choke, and then back down. Then engine will now die after a few seconds after what use to be a normal idle speed. It has so little power that it will take 10-15 seconds for the new high-lift blades to get up to speed while the engine is at full throttle :hammerhead: I recently changed the oil and the problem seemed to be fixed with the oil change (engine idled fine, blades went fine, etc), but I started the mower today and it's back, here's what the manual says...

    Engine Loses Power
    1. Low crankcase oil level. It's hard to tell the level with new oil so I'm not sure if this is the issue
    2. High crankcase oil level.
    3. Dirty air cleaner element. Nope, air filter's clean
    4. Dirt or water in the fuel system.
    5. Excessive engine load. Even when the Engine has no load it still struggles
    6. Engine overheated. Nope, even when the engine is just started it has issues.
    7. Faulty spark plug.
    8. Low compression.
    9. Exhaust restriction I did have to remove the muffler for the valve cover seal replacement, so this could be the cause

    Anybody know what could be the issues here?
  2. 44DCNF

    44DCNF LawnSite Bronze Member
    Messages: 1,563

    loose spark plug
    blown head gasket
    misadjustment of choke/throttle settings
  3. clean_cut

    clean_cut LawnSite Bronze Member
    Messages: 1,327

    I'm thinking it's not the throttle or choke, but the spark plug is a high possibility, it was removed during the recent service and may not have been put back in correctly. Blown head gasket? I hope not. I'll check the spark plug tomorrow, thanks!

    I'm guessing the power loss is due to the lack of compression as air escapes through the spark plug hole?
  4. laman

    laman LawnSite Senior Member
    Messages: 351

    Plug would have to very loose to lose a lot of compression..
  5. jetta

    jetta LawnSite Member
    Messages: 223

    have had 3 kohlers with 300 to 400 hr all have had out of round cylinders.now were trying kaws kohler was no help and no answers.
  6. clean_cut

    clean_cut LawnSite Bronze Member
    Messages: 1,327

    Thanks for the help guys, but I think I found the problem. I took off the carb bowl and washed it out and it runs a lot better. The idle still seems a tad off, but it runs much better now. There must have been some water in the bowl or something. Thanks for the help guys :)

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