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  1. #1

    Limp mode or maybe something else?

    I'm new to this forum so I'm not sure if I am in the right area to ask this question. I'm working on a 1996 Polaris SL780. I rarely work on Polaris and the few I have, never had this issue. It starts right up, idles great. I have no flashing red light or warnings on my display. My oil and fuel gauge all seem to work when I add fuel or move the oil sender float. The carbs have been gone through this week with all new needle/seat and the whole rebuilt kit, etc. However, it will not run past 5000 RPM. Right around 4000 RPM it smokes like crazy and starts to cut out and sputter like a limp mode. I have tried a different temp sensor, that didn't make a difference. I have also tried to unhook the grey wire from the CDI to the board, still no difference. My compression is kinda odd but I would say good, 150, 138, 141 with a blue point compression gauge. I have good spark on all three plugs, I have tried .15 and 0.25 plug gap. Any ideas?


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    4200 is right about where limp mode would come into play, but the gray wire not making a difference rules that out.

    The excessive smoke is a clue. Sounds like she's going rich for some reason.

    Run it until it happens and pull the lanyard. Take the plug wrench with you and see what the plugs look like.

    Might have a coil/stator failing under load. Had a similar issue once

  3. #3
    Thanks for the reply. I figure the limp mode is ruled out also, I'm really confused now. The plugs are definitely oily, not dripping wet with oil but if I could adjust the oil pump I would. It seems like it won't clean up after running wide open for awhile which is why I put new carb kits in right away. However, honestly the carbs looked perfect. Pop off pressure is about 21-22, filters didn't have a thing in them. Fuel pump also looks great, nothing cracked or odd looking. I will try a new coil but would like to try a new stator however I don't have one right now. Just don't want to buy parts I don't need. Would you assume it's definitely an electrical issue?

  4. #4
    Tried a new CDI unit - no change
    Tested the ignition coil.
    • I have 33 ohms from the plug wire to one of the two black wires.
    • I have 8.5 ohms from the same black wire and the inside of spark plug cap.

    Tried a different set of coils - no change.

    The carbs
    • high speed is at 1 1/2. Low Speed 3/4.
    • all new gaskets, seals, needles and seats.
    • pop off pressure is 21-22

    MFD
    Everything seems to be working good. Fuel and oil gauge work. Red light works but isn't flashing right now. I have no warnings.

    I have unhooked the grey wire from CDI to the board, no fix.

    Spark plugs all have spark. They are gapped at .15.

    Good compression.

    Just won't clear up past 5000 rpm. And smoke pretty bad.

  5. #5
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Did you pay attention to the oil pump linkage?

    The 780 uses a variable rate oil pump. So if you didn't install the linkage properly, the oil pump should go full open.

    Also make sure your choke isn't slightly closed.

    And the carbs are all in sync.

  6. #6
    Just did another compression check to double check what I have. 145, 142, 138. Pretty good I would say, popped the heads off, the cylinders look perfect, pistons barely have any time on them.

    Tested the Stator, ohms tested out within range so I didn't try a new stator.
    Red/Purple to Yellow .7 OHMS;
    White/Yellow to Black 213 OHMS;
    Blue/Red to Red/White 90 OHMS;
    Red/White to Green/Red 440 OHMS.

    Carbs are all in sync, they seem to be perfect.

    I'm not sure about the variable rate oil pump. How does that work? The linkage seems to be clicked in properly I don't see how it could be any different. The connecting rod between the carbs and the pump has a contour that bends around to fit in between the intake manifold. It's not hitting or rubbing anything, looks proper to me.

  7. #7
    Display randomly doesn't work now.. Doesn't light up anywhere at all. It is definitely clicked in, no corrosion. Just doesn't work today. Motor still runs the same.

    I tried closing off the oil line temporarily to stop the smoking, doesn't seem to make a difference.

  8. #8
    Finally runs right!! I decided to try a different stator and it fixed the issue. So, you can have an electrical part test with in range and still be bad. Learned something new. However, the Display now doesn't work. Has nothing showing up on the display as though it is turned off.. Any way to test this thing in case it works but I have something wrong?

  9. #9

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    yep the stators are tricky you can't go by the ohms testing sometimes

  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Did you check the fuse in the elec box?

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