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Husqvarna 580bts misfire

Discussion in 'Mowers and More' started by fatboycowen, Dec 5, 2017.

  1. fatboycowen

    fatboycowen Well-Known OPE Member

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    I've got a 580bts. It's about 3 years old, and it is only used by me, on my property. I'd guess I've got 10-15 tanks through it, so it's not that well used.

    Recently, it developed a misfire. I'm having trouble diagnosing.
    Starts normally. I usually let it idle a few minutes before using it. I'll start blowing leaves, and within a few minutes, it starts misfiring at high rpm. Just a constant, or on-off misfire. It continues to run, just with a high RPM stutter, that reduces the RPM.

    I changed out the spark plug, fuel line, fuel filter. I pulled the air filter (very clean). I pulled off the carb, and muffler. Muffler is not plugged up. Piston/cylinder look mint. It seems like it has great compression. I made sure the carb was sealing against the intake.

    I ordered a carb kit. Though, I'd hope it wouldn't need it, as it's only had non-ethanol fuel since day 1.

    The ONLY thing that i can think of is ignition related. I noticed the spark plug wire had some light chafing, where it goes over the cylinder cover. Somehow, the grommet disappeared. So, i ran it for a while without the cover on, so i could monkey with the wires. The misfire comes and goes. Moving around the wires doesn't seem to be effective.

    Thoughts?

    Thanks,
    Jon
     
  2. AVB

    AVB Well-Known OPE Member

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    Sounds like you are exceeding the max rpm limit of the coil (limited RPM) as it is speed regulated ignition system which should be set to approximately 7500-8000 rpm. It will misfire as you exceed the coil's preset limit.

    Try adjusting the top end speed to 7200 rpm or slightly less. The 580BTS max output is speced at 7200 rpm. If your rpms are below 7200 when it starts miss firing then coil is probably starting to fail. Also check your blower's fan for excessive wear or missing blades and that there is no restrictions. Restrictions will reduce the engine loading allowing it to exceed max rpms easily just like a vacuum cleaner motor.
     
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  3. fatboycowen

    fatboycowen Well-Known OPE Member

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    AVB. Thanks for the reply. Unfortunately, that's not the problem. When not misfiring, it runs at a steady 7200. When misfiring, it's much less. It's clearly a misfire, and not a limiter. Sometimes it will be a single or double stutter, sometimes continuous.

    So, here's what i've done so far. I pulled the carb, and dissembled. Ran it through the ultrasonic cleaner, and installed a new carb kit. I found the grommet for the ignition wire, and reinstalled it. Plug is new. Muffler is clean.
    I put it all back together, minus the rear cover, and ran it. It was night, so i didn't do any work, but i couldn't get it to misfire. It ran perfect. So, i figured it was fixed. I put the cover back on.
    Today, i went out to finish up the leaves i missed, before it snowed. A few minutes in, it started to misfire again. Unfortunately, i had a small pile of leaves in the driveway, and didn't want to leave them. So, i continued on, and moved them. I varied the throttle, so i wasn't constantly on the misfire. It misfired for a few minutes, then miraculously, the misfire vanished. I continued on, for about 20 minutes, and it ran PERFECT, without a single hint of misfire.
    Now I'm stumped. What could it be?

    Jon
     
  4. Moparmyway

    Moparmyway Its just a saw

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    Check the connection under the spark plug boot.
    If its loose or not connected well ....................

    When you say misfire ................ is it popping through the muffler or carb, or is it just like tapping the kill switch, it stops spark ?

    Any chance of getting this on video ?
     
  5. fatboycowen

    fatboycowen Well-Known OPE Member

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    I fully intended to get video, after I finished clearing the leaves in the driveway. But the problem disappeared. So, I never recorded it.
    I'll check that connection. Thanks.
    It's hard to explain the misfiring. I'm a car guy. Sounds like when a car has a misfire. Sounds like when a 4 cylinder runs on 3, kinda. Doesn't sound to me like a backfire.

    I'll check that connection, then try it again later, and see if the problem returns.

    Sent from my VS988 using Tapatalk
     
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  6. Moparmyway

    Moparmyway Its just a saw

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    If that connection is solidly made, the next time the miss happens (not a misfire), I believe youre going to need a new coil
     
  7. fatboycowen

    fatboycowen Well-Known OPE Member

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    Ok. Not sure what you mean by (not a misfire). But I'll keep that in mind, and get a coil next, if it comes back.

    Sent from my VS988 using Tapatalk
     
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