HELP! Kohler command 20 problem!

Discussion in 'Mechanic and Repair' started by Westbrooklawn, Aug 15, 2002.

  1. Westbrooklawn

    Westbrooklawn LawnSite Senior Member
    Messages: 427

    As I previously posted, I am having trouble with my Kohler command 20 on a Walker with 48" GHS. It is running rough, missing, and slight consistent backfire while running.

    I have drained and cleaned gas tank, lines, and carb. Installed new gas filter, air filter and plugs. Still running rough, and seems to be overheating very quickly, even after only a couple of minutes of running at idle. The high heat seems to be coming from only the front cylinder, to the point it heats the muffler to cherry red where that cylinder exhausts into the muffler....and only after a couple of minutes of running. Could this be a stuck or burnt valve? How can I test for that? I can borrow a compression guage, but not sure how to run the test properly. I know there are some great mechanics on this site......any suggestions??? Thanks!!
  2. barnard

    barnard LawnSite Senior Member
    Messages: 618

    definately sounds like aburned valve . Or else atight one. Disconnect the spark plug wires. set throttle in wde open position and crank it over a couple of seconds. (after removing the plug and while holding the compression tester in the spark hole-very firmly) . the compression should be 100-120 range.
  3. Ryan Lightning

    Ryan Lightning LawnSite Senior Member
    from CA
    Messages: 554

    Just incase you didnt know, Kohler has a 2 year warranty. Im guessing yours is older though?
  4. Westbrooklawn

    Westbrooklawn LawnSite Senior Member
    Messages: 427

    Yep....5 years old....out of luck!!!
  5. Westbrooklawn

    Westbrooklawn LawnSite Senior Member
    Messages: 427

    Finally got around to checking the compression......both cylinders are right at 170. I guess this means it's not a burnt valve? I am thinking now that it might be the coils.....but not sure how I can test them. Any suggestions would be appreciated.
  6. captdevo

    captdevo LawnSite Senior Member
    Messages: 932

    compression looks good.

    stuck valve is possible, or weak/broken valve spring. squirt a little marvel mystery oil in the cylinders and start it, or squirt some in the carb throat as it's running..(do this outside, it's gonna smoke)

    does it run rough as soon as you start it, or does it happen after it heats up?

    does it start easily cold/hot?

    cooling fins clean?

    pull valve cover and inspect.

    maybe blown head gasket.

    could have dirty carb., causing it to run lean.

    flywheel key sheared enough to offset timing and cause misfire.
  7. Westbrooklawn

    Westbrooklawn LawnSite Senior Member
    Messages: 427

    Captdevo -

    Thanks for the reply. To answer your questions, it starts easily both cold and hot, runs rough from the start but gets worse as it warms up, cooling fins are clean now but were not when this problem started, I've pulled both valve covers and valves seem to be operating properly while running, have cleaned carb out, and hadn't hit anything that would have sheared flywheel key. Also if head gasket was blown wouldn't compression have leaked down after I stopped cranking and let it sit? Any further suggesions would be greatly appreciated!!
  8. captdevo

    captdevo LawnSite Senior Member
    Messages: 932

    the fins were clogged.

    you probably have a blown head gasket, i've seen the compression tests show good and still have a blown head gasket, even a scored cylinder for that matter.

    i've seen them blown through into an oil port.

    when you removed the valve cover, was there severe dark discoloration around either valve?

    you don't necessarily have to hit anything for a key to shear, they can shear on a compression stroke or when an engine is shut down and reverses rotation.

    i would bet $$ you have a blown head gasket though, especially if the fins were clogged enough to overheat the engine
  9. Westbrooklawn

    Westbrooklawn LawnSite Senior Member
    Messages: 427

    Hmmmmm......... Thanks again for the reply...... I'm not a mechanic by any stretch of the imagination, but I have found I can fix about anything if I have the right instructions (either verbal or written manual). I guess I need to go ahead and pull the head. Hope it's as simple as a blown gasket! Any other helpful hints are always appreciated.
  10. John DiMartino

    John DiMartino LawnSite Silver Member
    Messages: 2,555

    When a Command blows a head gasket 99% of the time it blows it into the pushrod galley.I believe you have a blown intake gasket,This is just my educated guess.You do not have a blown head gasket if you have 170PSi on both cylinders,IMO.With it running spray some carb cleaner or starting fluid around the intake of the front cylinder,if it picks up ,and smooths out,youve found the problem. BTW with an intake gasket blown the front cyl will run really lean,and that will explain the red exhaust ,and high cyl temp,and lean missfiring/backfiring. John D

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