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  1. #1
    PWCToday Regular
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    951 carbed, no spark in rear cylinder

    It's a 98 model, at the lake it'll start up and idle, but won't rev up and will die. I check the plugs and the rear plug tip is clean no oil stains, the front plug looks normal with oil stain on the tip. So I'm assuming no spark to the rear cylinder, any idea what's causing this or what needs to be replaced?

    It has a new stator, new bendix gear, new battery and it's getting faint sound of the two beeps with lanyard attached.
    carbs have been cleaned, fuel selector valve bypassed, and fuel lines changed.
    Last edited by pwc enthusiast; 05-11-2017 at 05:24 PM.

  2. #2
    PWCToday.com Is My Home Away From Home Grumpy Old Guy's Avatar
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    Re: 951 carbed, no spark in rear cylinder

    Cant happen as both plugs fire at the same time.

    Dont assume,check for spark. Then check compression,my guess is something was not done right in the carbs or could be a broken reed.

  3. #3
    I dream skis
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    Re: 951 carbed, no spark in rear cylinder

    Could be a poor wire connection, in the spark plug wire.

  4. #4
    PWCToday Guru Bionic racing's Avatar
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    Re: 951 carbed, no spark in rear cylinder

    With out compression fuel won't burn and change color , at this point pull plugs and put finger over plug hole and crank , that will let you know what's up

  5. #5
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: 951 carbed, no spark in rear cylinder

    Quote Originally Posted by Grumpy Old Guy View Post
    Cant happen as both plugs fire at the same time.

    Don't assume,check for spark. Then check compression,my guess is something was not done right in the carbs or could be a broken reed.
    Good Advice


    Quote Originally Posted by pwc enthusiast View Post
    It's a 98 model, at the lake it'll start up and idle, but won't rev up and will die.
    I check the plugs and the rear plug tip is clean no oil stains, the front plug looks normal with oil stain on the tip.
    So I'm assuming no spark to the rear cylinder, any idea what's causing this or what needs to be replaced?
    Obvious it isn't running on the rear cylinder.

    Stop trying to run the engine, you could make the problem worse.


    My advice is check the compression.


    If there is any raw gas inside the cylinder, it can be dangerous to
    check the spark.To prevent an accident:

    When you check the spark, do it with the old spark plugs in their
    holes. Ground a set of new test spark plugs against the old spark
    plugs in the head. Then test the spark.

    It is easier to see the spark on non-resistor spark plugs.


    Bill M.
    Last edited by wmazz; 05-12-2017 at 01:07 AM.
    Horsepower == Speed, RPM != Speed



  6. #6
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    Re: 951 carbed, no spark in rear cylinder

    I tried checking compression and it shot up to 190psi because it was flooding with fuel in the rear cylinder.
    I removed compression guage and cranked it over to get the fuel out and it just keeps shooting a load of fuel out evertime the engine cycles. So now i can't check compression, and the fuel is washing away the oil stain on plug tip, and since they spark at the same time, I'm guessing I have spark and the issue is in the carbs not electrical.

  7. #7
    PWCToday Guru Bionic racing's Avatar
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    Re: 951 carbed, no spark in rear cylinder

    Where are you located in california , if close to me bring it here and have diagnosed in 5 minutes , no guesswork

  8. #8
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    Re: 951 carbed, no spark in rear cylinder

    Quote Originally Posted by Bionic racing View Post
    Where are you located in california , if close to me bring it here and have diagnosed in 5 minutes , no guesswork
    I gave you all the symptoms, what's the diagnosis?

    also I shouldn't say im guessing I have spark, I do have spark because I was able to idle the ski to the island where we post up.
    Thanks in advance.
    Last edited by pwc enthusiast; 05-12-2017 at 12:12 PM.

  9. #9
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: 951 carbed, no spark in rear cylinder

    Quote Originally Posted by pwc enthusiast View Post
    I tried checking compression and it shot up to 190psi because it was flooding with fuel in the rear cylinder.
    That is how fires get started, that is why I made this recommendation.

    Quote Originally Posted by wmazz View Post
    When you check the spark, do it with the old spark plugs in their
    holes. Ground a set of new test spark plugs against the old spark
    plugs in the head. Then test the spark.

    It is easier to see the spark on non-resistor spark plugs.
    You will be fortunate if it turns out to be a broken reed as Grumpy Old Guy
    suggested, or a problem with the needle and seat leaking.

    If the lever height is too high, the seats will leak as soon as the float diaphragm
    is installed. So if you tested pop-off like normal, the seats will leak after final assembly.

    I would test pop-off immediately after they were pulled off, while the carbs are still
    assembled. Do you need help with making your own pop-off tester.

    Because it was an ~early 951, I was leaning towards a water damaged
    piston that has seized, and lost compression.

    But I sincerely hope it turns out to be an easy fix.


    Bill M.
    Last edited by wmazz; 05-12-2017 at 04:02 PM.
    Horsepower == Speed, RPM != Speed



  10. #10
    PWCToday.com Is My Home Away From Home Grumpy Old Guy's Avatar
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    Re: 951 carbed, no spark in rear cylinder

    You have a carb issue.

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