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  1. #1

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    98 seadoo 951 back fires while cranking.

    Hi everyone,I have had this Isue with my 1998 seadoo GTX ltd twice.I've got to the ramp.warm up my engine while still out of the water,i put it in the water and when i'm all ready to go i push the start buton and instead of get the engine to run,it back fires thrue the exaust (it's very loud too)and it blows the exhaust hose an plenty of water starts coming into the hull.any idea why this is hapening???has it hapened to any of you?? By the way,if i pump the primer before cranking the motor it won't hapend.I'll ipreciate any help.


  2. #2
    wkuadam07's Avatar
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    Why do you warm it up out of the water? My guess is that you are getting excess gas in the pipe at the shutoff from warmup... when you start that gas goes off... If the engine is in good condition and running properly you should drop it in the water, start it, warm it up while leaving the no-wake zone, then have fun.

  3. #3
    m schmidt's Avatar
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    Quote Originally Posted by wkuadam07 View Post
    Why do you warm it up out of the water? My guess is that you are getting excess gas in the pipe at the shutoff from warmup... when you start that gas goes off... If the engine is in good condition and running properly you should drop it in the water, start it, warm it up while leaving the no-wake zone, then have fun.
    I always start my ski before it leaves the the driveway. And then at the ramp. It's nice to know if you have problem at the house instead and the water.

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  5. #4
    If i knew,...I wouldn't ask sea-one's Avatar
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    seriously, who would leave the house without making sure its ready to go instead of looking THOOPID at the ramp..If your one of those out there, i assure you im calling you names..

  6. #5
    wkuadam07's Avatar
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    Quote Originally Posted by sea-one View Post
    seriously, who would leave the house without making sure its ready to go instead of looking THOOPID at the ramp..If your one of those out there, i assure you im calling you names..
    BE NICE... i start it at the house too though sometimes to check operation. But this guy said he "warms it up" on the ramp...

    As for you schmidt... i bet you wear out a lot of starters... LMAO

    Bottom line here is your craft is water worthy or not, it's a 1 or a 0, it's a yes or a no. No grey area. No maybes, if it's a maybe then you should keep wrenching or you will be getting towed in (looking THOOPID).

    So back to helping this guy already!!!!! And no more insults for the new guy to the forum (me)!!!!! I may be new to the forum, but i can wrench and ride 2 stroke skis with the best of them. I have never seen a ski backfire...but i didn't see anybody else try to help... so i offered my $.02.

  7. #6
    Two strokes will back-fire through the exhaust due to the pipe being loaded up with fuel.. This can happen because of fouled plugs, leaking carbs, excessive choke or primer...

    This is also a DC-CDI ignition system - the spark is very dependent on battery voltage... If you have a high starter draw or a low battery voltage, you could actually have an ignition miss fire..

    When the unit is in the water you also have a slightly higher cranking load and a higher starter current draw..

    What's common most of the time is you will be cranking and as soon as you let go of the starter button the unit will backfire or start.. This is due to low ignition voltage while cranking..

    Two suggestion, remove and clean carbs - and test your battery voltages while cranking... Black or wet plugs are considered fouled and could be the cause or indication of this issue.

  8. #7
    icdoo's Avatar
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    Lets keep it simple first. Try fresh gas and new plugs correctly gapped. Im guessing the fuel cause I've had it happen on skis and sleds before

  9. #8
    AndinoWatercraft's Avatar
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    Ask our friend seadooer what jet size he's running . Bet you all be surprised lol..... I think there may be part of the problem.

  10. #9

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    Cool

    Quote Originally Posted by AndinoWatercraft View Post
    Ask our friend seadooer what jet size he's running . Bet you all be surprised lol..... I think there may be part of the problem.
    Do I read a jolwosly coment? LOL.... I'm runing drilled low speed jets to a size that's watever bigger than 110,1 turn out low speed screw,165 main jets,1-1/2 turns out hi speed screw,95g spring and 2.3 needle seat.


    1mm over size bore pro-x pistons
    mild ported exaust (just enouth to match the sleeves)
    home made intake plenum
    cylinder deck milled to 1mm
    165 psi compression on both cylinders
    stock pipe
    stock waterbox
    stock reeds
    stock mpem
    eliminated rave solenoide
    eliminated water regulator


    It does run kinda rich at idle so I'll be re tuning my carburators.m
    akes sense to me that the rich condition might be causing all the issue.thaks veryone for th replying.

  11. #10
    SURFnTURF's Avatar
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    Check your N/Seat is holding pressure and not leaking

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