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2003 Lazer HP backfires REALLY bad

Discussion in 'eXmark' started by TurfPro, Jun 29, 2003.

  1. TurfPro

    TurfPro LawnSite Member
    Messages: 232

    1st off I'd like to say I'm EXTREMELY pleased with my Exmark Lazer HP,,,it's been a real asset to my business. But i am having one problem that concerns me... I'm a stickler when it comes to any of my equipment,truck , etc,I want them to be well maintained and well,,, right. So I am quick to notice things that seem a little "outta wack" hopefully to prevent any serious damage.
    Here's what it's doing,you all tell me if it's a problem :
    The HP has the 23hp Kohler and when I have ran it for ,oh, say an hour or more,and try to shut it down,it will "diesel" and then backfire at least once,but usually more like 2-3 times. .... here's what I've tried to remedy the situation:
    (1) I've tried to let it idle for 15-30 secs before shutting off
    (2) let it cool down at 1/2 throttle or less and then shut down
    (3) shut down and then as its dying, increase throttle
    (4) tried using the choke at shut down......
    (5) A/Filter is clean (new/replaced) s/plugs new (50hrs on machine)
    I don't know what else to try ,please provide me with some suggestions.

    If you want me to take it to my dealer please contact me by private message on this forum.
    Thank You
  2. 65hoss

    65hoss LawnSite Fanatic
    Messages: 6,360

    Seems all new motors do this even more than a broke in motor. I found a way to stop mine and let the motor cool at the same time. I shut the fuel off and let it run it out. No backfire and the motor cools before shutdown. Thats how I do it anyway.
  3. TLS

    TLS LawnSite Fanatic
    Messages: 7,943

    Many times engine manufacturers set idle speed too high.

    I found that lowering idle speed a bit allows motor to spin slower (duh) and when you shut down, increase throttle to 1/2 immediately. This has stopped ALL backfires in all my machines.

    Seems like the wrong thing to do, but it works.

    Now, don't allow the engine to idle at this new LOW idle speed for to long, as oil pressure is pretty low at this speed, and cooling for an A/C engine is decreased. But, cut down to low idle, switch off ignition and immediatly raise throttle.

    Works for me.
  4. TurfPro

    TurfPro LawnSite Member
    Messages: 232

    Thanks for the replies guys,,,but this is not your standard Kohler backfire . It'll diesel for several seconds,studder,and try to restart,rev up and down,etc.

    My buddy has a 23 Kohler and a 23 Kawi and neither do what mine does. Mine used to have the "kohler backfire" but it has steadily got worse to the point it is now. Nothing wit hthe throttle makes any difference.
  5. ACut AboveLandscapin

    ACut AboveLandscapin LawnSite Member
    Messages: 42

    I have had two lazer Z HP with the 23 HP engine and both of them backfired for at least the first 1 hundred hours.

    I brought mine to the dealer and he adjusted the engine speed which corrected the problem.
  6. eXmark

    eXmark Manufacturer / Sponsor
    Messages: 4,258


    The truth is all the engines available today will backfire. The only question is how often and how severely.

    The cause is generally raw fuel making it to the hot internal components of the muffler. The fuel then ignites making a distinctive bang that can be heard by customers and neighbors on both sides of the block at several houses in each direction. The "dieseling" is just a twist on the same basic theory.

    In the dieseling process the raw fuel is "pre-igniting" in the combustion chamber which cause the engine to spit, cough and shake as if it's been invaded by gremlins.

    Most generally the "dieseling" can be eliminated and the backfiring can be reduced simply by shutting the unit off at half throttle or above.

    Neither situation is good. The backfire's can over time loosen the baffles inside the mufflers that have become weakend simply by all the heat and condensation from cooling through normal use. The "pre-ignition" can put additional stress on engine componants over time. This is probably not a huge issue unless there is a weak componants somewhere.

    Hoss is correct shutting the fuel off will eliminate any possibility of either "backfiring" or "dieseling".

    Let us know if you have any other questions.


  7. TurfPro

    TurfPro LawnSite Member
    Messages: 232

    Thanks Terry,

    I'll try to shut it off at a higher speed and see if that helps........... If it doesn't I'll let you know ;)
  8. TurfPro

    TurfPro LawnSite Member
    Messages: 232

    Ok , tried the higher RPM shut -off,,no change,,actually it "dieseled" worse than ever. It seems as though the hotter it gets the worse it gets. .........
    I also tried shutting off the fuel and that cured the problem,but who wants to wait 5-7?? minutes everytime you shut it off? I have some very wide spread properties where I have to mow ,edge ,trim,& blow each section before going to the next,so shutting down alot each day is a part of my daily routine.
    Thanks for any input
  9. eXmark

    eXmark Manufacturer / Sponsor
    Messages: 4,258


    If you don't want to take it to your dealer to have them look at it, I would go straight to the horses mouth - Kohler. Contact them, explain what you've tried, and work from there. It sounds like you've tried some of the easy fixes without any luck.

    Call this number - 800/544-2444. This is Kohler's Customer Service number. You could also e-mail them. Here is a link to this portion of their web site - http://www.kohlerengines.com/contact.html. If I were you, I would probably give them a call. Make sure that you're near the mower (if possible), and have the model, spec, and serial number of the engine handy. I'm sure they'll want this information. Let us know what happens.

    Talk to you later,

    Exmark Customer Service
  10. Jman

    Jman LawnSite Member
    Messages: 217

    Try reading the Kohler owners manual. Shut the engine off with the throttle at least 3/4 open. I say leave it wide open when you shut it down. There is a fuel shut off solenoid in the high speed jet, it does not shut off the idle jet. When you shut down at wide open throttle, the solenoid closes, you don't wash down the cylinder with fuel, none gets thru, the oil pump is constantly pumping oil, so no bearing goes without lubrication. Try it.

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