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  1. #1

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    run away seadoo?!?!

    so, my engine would run fine for about an hour then start bogging at anything over half throttle. well i used the handy dandy search function and found out how to clean the carbs and their filters and yada yada yada. all went well, cleaned it and threw it back on. put new non ethanol gas into the tank and i start it on the water hose "the proper way" and it idles like a dream around 3k. i tap the throttle a tad and BOOM it shoots to 7k rpms, the throttle was not pushed, so i kept calm and pulled the lanyard. wtf the thing kept running, pulled the wires from the top of the spark plugs THE DAMN THING KEPT RUNNING! so i panicked and grabbed a handfull of fuel line and pulled the return line off the top of the carb. it shut off thank the lord, but i broke the fitting that the connects the hose to the MAG carb and follows out the other side to the PTO side carb. so i need to find a place to buy that fitting, and HOW ON EARTH is my engine revving so high without the throttle pinned? i checked my cables and linkages and nothing was binding. i seriously need help here, the sooner the better. and no i do not have the grey fuel lines on my ski.


  2. #2

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    it is a 1998 seadoo XP, sorry should have mentioned that :P

  3. #3
    rhyne717xp's Avatar
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    Lean runaway condition, maybe an airleak at carb base gaskets, not enough fuel to carbs, fuel valve in the OFF position. A number of thangs it could be.

    Any time working on a fuel system you should prime the fuel system by pumping some ai r into the return to fuel tank line and have a Gatorade type bottle to catch the fuel from the 45 tee wye.

    More than likely the carbs didn't have a steady stream of fuel bc of air in the lines.

    Next time your motor runs away pull the choke, or primer valve.

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  5. #4

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    good idea on the choke! and i will look into the lean condition, i put the carbs back togethor the exact way i took them out, maybe i connected a fuel line in the wrong spot but the dry carb idea sounds very very possible as this was the first time running it since the carbs were apart!. i have figured out how im going to fix the hose fitting, tomorrow but ill prime the carbs and see how she does. probably wasnt a good idea to give it gas right as i started her up anyways, that definitely would give me air in the fuel lines.

  6. #5
    rhyne717xp's Avatar
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    Quote Originally Posted by brblommel View Post
    good idea on the choke! and i will look into the lean condition, i put the carbs back togethor the exact way i took them out, maybe i connected a fuel line in the wrong spot but the dry carb idea sounds very very possible as this was the first time running it since the carbs were apart!. i have figured out how im going to fix the hose fitting, tomorrow but ill prime the carbs and see how she does. probably wasnt a good idea to give it gas right as i started her up anyways, that definitely would give me air in the fuel lines.
    Make sure the pulse line is hooked up, it drives the fuel pump.

    The choke is your best allie in a runaway condition.

  7. #6
    Myself's Avatar
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    Usually that's exactly how it happens after a carb cleaning or rebuild. Fire it up, idle a bit, blip the throttle and all hell breaks loose.

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  9. #7
    The 951's run away easily. If there are no air leaks, the most common things are too high an idle (set at 2800 out of water), or throttle cable too tight.

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  11. #8

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    i didnt change the idle settings on the carbs, but i might have put the throttle cable on too tight. ill look into that tomorrow, just kinda freaked me out that it kept running after the plugs were removed. lol

  12. #9
    You said it idles at 3000. Set it to 2800.

  13. #10
    Just FYI, the 951 engine was purposely made to run really lean at just off idle, at around 3000 RPM on the hose. People that don't know this fact always assume that there is something wrong, because most 2 stroke engines will runaway if there is a lean condition. A lot (not all) of 951 engines will runaway if the idle speed on hose is set too high, say 3200 or higher. But some runaway at 3000, which is the speed that the service manual tells you to set it at. This is why Wire4money's advice is good, many guys set it at 2800 to keep them from running away. And if your throttle cable is too tight (it MUST have slack!), you will runaway....

    I have a theory that the 951 engine runs away, (technically called "auto-ignition") not from plug glow-plugging like most people think, but from exhaust gas re-ignition. This is where the chemical reaction of burning is not totally complete, and the leftover exhaust gas that is still technically "burning" ignites the incoming mixture. This phenomenon is actually used in some exotic (mostly experimental) engines to ignite the next charge. I am involved on an automotive engineering forum, and posed this question to several experts on this, and they agree with my theory as being most probable. I have not taken the time to prove this, which would be to install a window into the head and IR measure the plug tip during runaway to prove my theory. (I've got more pressing issues than this on my plate at the moment...)

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