SBT Jetski Engines, Parts & Accessories

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  1. #1
    Joined
    May 2006
    From
    Lansing
    Posts
    10

    Default Possessed engine

    I purchased a new short block for my 1999 xl 1200 ltd from sbt. Installed it, and just had the weirdest thing happen. I started the engine, and it was running rough, so I adjusted the idle screw, and it seemed to smooth out, but was still acting kind of weird. I turned off the engine, and started it again, it quickly rose to about 6k rpm, so i figured i set the idle screw to high. I went to stop the motor, and that is when it got weird. I hit the stop button, but nothing happened, the engine kept running. I pulled the lanyard kill switch, but nothing happened, the engine kept running. I turned the fuel switch to off, gave it about 30 seconds, but nothing happened, the engine kept running. I then pulled off all 3 spark plug wires, but nothing happened, the engine kept running. I was pretty freaked out at this point. It ran for about 1 minute with the fuel shut off, and all 3 spark plug wires unplugged. Then for some reason I decided to blip the throttle, and it finally died. Any ideas????? Also, would it running at this high rpm during break in cause any engine damage?

  2. #2
    Joined
    May 2005
    From
    Indian Rocks Beach, FL
    Posts
    16

    Default Re: Possessed engine

    Is your house built over a graveyard?

  3. #3
    Joined
    May 2006
    From
    mississippi
    Posts
    2

    Default Re: Possessed engine

    sounds like engine was flooded as for running after the plug wires were pulled could have been deiseling or running from heated engine check carbs to make sure not flooding:emoticonw

  4. #4
    Joined
    May 2006
    From
    Lansing
    Posts
    10

    Default Re: Possessed engine

    I googled dieseling and that makes sense. If my idle was to high, the throttle plate on the carbs would have remained open enough to keep feeding the engine gas, and the hot engine would have used the built up red hot carbon in the cylinders to ignite the gas. thanks james

    But now, if the engine got hot enough to ignite itself and keep running, did that cause internel damage? Its my understanding that you can run a pwc engine for 10-15 minutes without any cooling before you risk damage, but only at idle speeds. My engine ran at 6k rpm for about 1 minute, but it didnt feel hot to the touch.

  5. #5
    Joined
    Mar 2003
    From
    SBT
    Posts
    21,545

    Default Re: Possessed engine

    It's called glowplugging. It's caused by air leaks and user error. In this case, most liely your idle too high, and you running the ski off the hose, overheating it.

    In the future, adding gas kills it. Pull the lanyard hit the primer (throttle in your case) and/or pull the choke.

    Yes, if it really ran for 1 minute, you have damage. How much - no one can guess. Take a compression check.

    Now if you are exagurating, and it was more like several seconds, you are probably fine.
    SBT Tech Support is here to help with your problems.
    We try to answer each question quickly and accurately.
    Please do not use Private Messaging for Tech Support, use the forums.

  6. #6
    Joined
    May 2006
    From
    Lansing
    Posts
    10

    Default Re: Possessed engine

    Compression check shows exactly 113 on all three cylinders.

  7. #7
    Joined
    Mar 2003
    From
    SBT
    Posts
    21,545

    Default Re: Possessed engine

    That's fine.
    SBT Tech Support is here to help with your problems.
    We try to answer each question quickly and accurately.
    Please do not use Private Messaging for Tech Support, use the forums.

  8. #8
    Joined
    May 2006
    From
    columbia, sc
    Posts
    12

    Default Re: Possessed engine

    just for reference, you can pull the choke if equipped or block off the intake. if it can't get air, it can't run away. never seen the throttle cause this problem, usually i find that the engine either has an air leak, the carb settings are wrong, or even too much water pressure from flush hose.

  9. #9
    Joined
    May 2006
    From
    Lansing
    Posts
    10

    Default Re: Possessed engine

    The engine seems to be running perfect now.


    I took off the carbs and noticed that my throttle plates were out of sync. When one was closed completely, one was open about 1/16", and the other was open about 1/8". I dont know if that would cause the dieseling, but it definitely was the cause of my rough idle, and inconsistent rpm issue i was having. I never thought to look at the throttle plates, because I never touched them when I rebuilt the carbs, but they must have been out of sync on the original engine.

    So Technical Support was correct, "user error". But I dont know about the air leak part, because I thought I'd still be having other kind of problems if I had an air leak?

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