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Thread: Blown Piston

  1. #1
    Joined
    Mar 2006
    From
    Molokai,Hawaii
    Posts
    5

    Default Blown Piston

    after 5yrs in storage, my cousin gave me his 95(he thinks)seadoo GTX.sends it to me via boat,then tells me the PROBLEM! It boggs out on the start and ocassionaly dies out.Well three weekends i rode it felt the bogg but did not die out.Then this weekend OH YEAH it died! Took out the spark plug and one plug only is really shot.Looked in the cylinder and theres a hole!What would be the cause of that and the bogg?Also how can i find the year and size engine to buy some parts?THIS TURNED INTO A CAN OF WORMS!!!!!!!!!!!!!!
    Last edited by Can Of Worms; 03-06-2006 at 02:12 PM.

  2. #2
    Joined
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    21,545

    Default Re: Blown Piston

    The last two digits of the VIN tag on the back of the ski are the model year. Look at the engine ID tag on top of the flywheel for the engine size. Post a picture and we can tell you for sure what it is. You'll need to pull the engine and disassemble it for inspection to figure out exactly what went wrong.
    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.

  3. #3
    Joined
    Nov 2003
    From
    Glendora, CA
    Posts
    6,846

    Default Re: Blown Piston

    You have a 720 engine. Most likely, The carbureator is clogged up with debris and it ran lean on that clyinder, burning a hole in the piston. The fuel selector valve may be clogged up too.

    Next time, when your pwc is not running right park it and fix it. By continuing to run it, you spent an extra $1000.00 or so that is unnecessy, and you still need to fix the carbs and fuel system.
    Bill O'Neal <br>
    WCM
    <a href="http://www.watercraftmagic.com"

  4. #4
    Joined
    Mar 2006
    From
    Molokai,Hawaii
    Posts
    5

    Default Re: Blown Piston

    here's pic of the tag in the motor.Another problem is theres no shops on this tiny island so ineed info to order the right parts get a manual and try to fix or sink it
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    Last edited by Can Of Worms; 03-06-2006 at 05:24 PM. Reason: add

  5. #5
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    Default Re: Blown Piston

    First, wrong spark plugs. Only use NGK BR7ES. Second, that's (obviously now) a 657 engine. If those spark plugs are of too hot a heat rnage, you could have very possibly burned the hole in the piston that way. No matter what, you now need a new engine.
    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
    Mar 2006
    From
    Molokai,Hawaii
    Posts
    5

    Default Re: Blown Piston

    could i just get a top end rebuild kit!motor still turns over

  7. #7
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    Default Re: Blown Piston

    When you melt a hole in the piston, the crank bearings are contaminated, and the crank needs to also be replaced.
    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
    Jan 2006
    From
    virginia
    Posts
    3

    Default Re: Blown Piston

    Quote Originally Posted by Can Of Worms
    could i just get a top end rebuild kit!motor still turns over

    top in rebuilt kit fixed mind ,and cleaned carbuetors ,still running find .
    never run engine when not running on both cly's .
    ;) Fixerupper

  9. #9
    Joined
    Mar 2006
    From
    Molokai,Hawaii
    Posts
    5

    Default Re: Blown Piston

    took apart cyl.no scratches visible,what size piston do i need to order?everything is bone stalk.what size carbs are on this can of worms.i just wanna order right parts(piston's,carb rebuild kit;etc,):emotredf

  10. #10
    Joined
    Aug 2001
    From
    Las Vegas, Nevada
    Posts
    1,220

    Default Re: Blown Piston

    Quote Originally Posted by Technical Support
    First, wrong spark plugs. Only use NGK BR7ES.
    Actually Champion Power Sport #8415 is the correct Spark Plug for the 657 engine. It is not an NGK, but it is a plug that is engineered specifically for the Power Sports market. I've had pretty good luck with them especially in the Sea-Doo Jet Boats.
    John Kubiak
    Powersports Technical Training Professional
    Las Vegas, Nevada
    Sea-Doo Tech 13736
    PWC Tech since 1988 (22 years)
    PowerSports since 1976 (34 years)
    NEVER BUY TIRES AT A "BLOW-OUT" SALE
    Please do not use Private Messaging, use the forums.

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