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  1. #1
    brad148405's Avatar
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    Sl 780 alive (sorta)

    After replacing alot of parts on a previously sunken 780... we got it to run, sorta... we replaced the started, bendix, flywheel, and stator. CDI box has been gone threw no moisture nothing is lose... had a guy work with me it he adjusted the carbs to spec and the thing will run about 35-40mph... maybe a little faster.. (my SLT700 smoked it, which we all know shouldnt happen) my mfd used to work... we hooked up a 750 cdi before during troubleshooting... then found out that wasnt the cause... so we replaced the orginal 780 CDI. Ic annot tell if its in limp mode or not, ( I have experienced it before and that made the ski run alot slower). Here are the problems right now (I will list to make easier)

    1.) Idles rough (not too bad though) ( sometimes will die on its own)

    2.) pushing the starter in does not start it, Have to hold the throttle down as well then give it gas to start and go almost WOT to keep it running.

    3.) For some reason, that SL 780 is hard to turn, (has no sponsons but a R&D intake grate... does that sound normal? I was on choppy water.


    Things I have done,

    checked the fuse in the CDI, none were blown... Pulled the gray wire/tan wire no change... no corrosion anywhere in the CDI box

    spark plugs were clean (not black)

    with these carious issues could I get some help from my fellow green hulkers on getting this beast revived once and for all?

    a list of what to do/try next would be awesome.. thanks!


  2. #2
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    Sounds like its rich on the idle circuit. Maybe leaky float valves, not seating. Did you find the clean plugs wet? Was a pop off test checked on the carbs? With the F/A off and idling, can you see fuel dripping onto the throttle plate?

  3. #3
    brad148405's Avatar
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    yes the plugs were wet

    I have no performed a pop off test, never have... is it difficult to do? what all is needed? and for the second question what is F/A? lol (sorry for stupidity)

  4. #4
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    Popoff test and more can be found in the mikuni manual. The F/A is the flame arrestor sometimes called air filter.

  5. #5
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    For the test gauge look here.

  6. #6
    brad148405's Avatar
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    Ok I will have to try that after work...

    what would be my next steps with the MFD and the steering issues?


    I did notice when I opened her up that rubber boot that connects the exaust system together had a big rub mark/gash in it when it didnt before... (found out the moron that was working on it didnt replace the bungee cord so the water box was bouncing all around) do you know where I can find one of the boots?

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by brad148405 View Post
    ...what would be my next steps with the MFD and the steering issues?

    I did notice when I opened her up that rubber boot that connects the exhaust system together had a big rub mark/gash in it when it didn't before... (found out the moron that was working on it didn't replace the bungee cord so the water box was bouncing all around)

    do you know where I can find one of the boots?
    For used parts sources, have a look at this list.

    Regarding the MFD; confirm the 1/4 Amp fuse inside the electrical box is good. Check that the Red/Purple and Black wires that connect to the MFD are properly connected inside the electrical box.

    Does the MFD wake up at all when you unplug and reconnect it to the MFD connector?

    Wat do you mean by hard to turn? Does the steering handle bar operate easily, but the machine doesn't actually want to change direction?

  8. #8
    brad148405's Avatar
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    I will try the MFD unplugging and plugging back in.. the fuse is good, we checked it. It worked before now its not working...

    yes you can move the handles bar easily.. but it will not turn easily... (this does not have sponsons by the way)

  9. #9
    brad148405's Avatar
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  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by brad148405 View Post
    CDI box has been gone threw no moisture nothing is lose... had a guy work with me it he adjusted the carbs to spec and the thing will run about 35-40mph... maybe a little faster..

    1.) Idles rough (not too bad though) ( sometimes will die on its own)

    2.) pushing the starter in does not start it, Have to hold the throttle down as well then give it gas to start and go almost WOT to keep it running.

    3.) For some reason, that SL 780 is hard to turn, (has no sponsons but a R&D intake grate... does that sound normal? I was on choppy water.


    Things I have done,

    checked the fuse in the CDI, none were blown... Pulled the gray wire/tan wire no change... no corrosion anywhere in the CDI box

    spark plugs were clean (not black)

    with these carious issues could I get some help from my fellow green hulkers on getting this beast revived once and for all?

    a list of what to do/try next would be awesome.. thanks!
    You need to see if there's any corrosion on the bottom of the circuit board, not just the top.

    Carbs were adjusted to spec.... For what model year?

    Clean, wet plugs sounds like it's rich. So, I doubt they were adjusted correctly.

    Holding throttle open to start indicates a rich mixture. Open throttle lets in more air to lean the mixture out. (carb adjustment)

    What do you mean hard to turn? Handle bars move freely? Does the steering nozzle move freely with the bars?

    Where was the trim set at? (steering and speed issue maybe, if set all the way up)

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