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  1. #1

    Engine Boggs and dies near 4000

    96 slt 780 rebuilt engine, carbs, fuel pump etc took it to the lake today and it ran ok, idles etc. when you throttle up it dies between 3800-4000 almost acts like a rev limiter. It feels like it loses one cylinder, pulled the plugs and they all match, not fouled etc. Seems like it might be fuel
    related. I disassembled the fuel pump, inspected and installed a new
    diapram. I might have timed the housing wrong. I am going to check the compression just for sh*ts and giggles. I am probably going to remove the fuel pump and diassemble again. Anyone ever encountered this problem before. Oh, I had to cut the fuel sender wires. Guess it is bad, was full show empty and blink blink fuel arggghhhh that was agrevating. How do you adjust the trim on these damn things??
    thanks everyone..

  2. #2
    please see pics of plugs, I tried to take some good ones but I am no photo man.. Plugs are not wet. Golden brown, One is slightly blackish brown, there is maybe one hour of tune time on them, they never changed colors..
    Last edited by gvnitup; 05-29-2010 at 08:11 AM.

  3. #3
    axgrider73's Avatar
    Join Date
    Feb 2007
    Southeast Ohio
    Quote Originally Posted by gvnitup View Post
    Oh, I had to cut the fuel sender wires. Guess it is bad, was full show empty and blink blink fuel arggghhhh that was agrevating.
    Sounds like your ski is running in limp mode.

  4. #4
    Alright, I removed the fuel pump, checked and no problems there. I removed the carbs, went all the way back through them. They are fine. Compression shows 120-122-125 thats fine. Again, I cut the fuel sender wires. But, I dont think that would cause this. If you get on the throttle hard it takes off like a bat out of hell, then bogs. let up on the throttle slowly you can get to 26-28 miles an hour 3800-4150 rpms max. All the while it sounds like it dropped a cylinder.. Please, help me go somewhere.
    I did not set the timing after the engine overhaul but I did mark the stator.. Really dosent seem like thats the problem, seems like Choking, maybe starving for air, not a derate. really weird.. I must be missing something simple..

  5. #5
    axgrider73's Avatar
    Join Date
    Feb 2007
    Southeast Ohio
    Most skis have a saftey feature known as "limp mode". If the ski get too low on oil, gas or over heats a rev limiter kicks in and limits the rpms to around 3500-4000. Limp mode is designed to allow you to get to shore without ruining your ski.

    I am not an expert, but it sounds like the cut fuel sender wires are making your gauge read empty sending your ski into limp mode. It might be worth the time to reconnect the wires and see if that fixes your problem.

  6. #6
    I agree, I have tried them both ways, when i cut the wires. That damn little light stopped flashing.. But it did run like crap both ways..

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
    Join Date
    Oct 2006
    Cleveland OH
    Check the float inside the fuel sender unit. If it sinks in fuel replace it and reconnect your wires. No more limp mode.

  8. #8
    absentx's Avatar
    Join Date
    Aug 2006

    If the problem was in the sending unit, then snipping the wires isn't going to do anything, because the system still thinks your low or out of fuel.

    Check the sending unit for proper operation, or solder a resistor into the snipped lines from the sending unit.

    I assume you want a fuel readout though, so I think checking the sender would be the best option.

  9. #9
    Yup, I odered a new fuel tank float. But wanted to ride and make sure this fixed the issue. I installed a 33 ohm resistor and took the unit to the lake. It was a big big difference It topped out at 51 mph on a very choppy lake.
    I just want to say thanks, And wow what a difference.

  10. #10
    Moderator beerdart's Avatar
    Join Date
    Aug 2006

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