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  1. #1
    Master of the Dooniverse
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    1997 SLT 750 Rev Limiting

    I have an SLT 750, pretty sure the year is '97, could be a '96. Anyhow, it fires up and idles just fine, but when you gas it thru full at about 3500 it just starts very cleanly misfiring, like it's rev limiting. I can see fuel shooting into all three carbs, everything is super clean on the ski. I'm assuming there's a bad connection someplace just ads I've seen on the Doos when the coil ground is bad/loose.

    Just wondering if any of the more Polaris friendly guys could point me a place to look first, known issue grounds, that sort of thing. I have some experience with Pol, but by no means a guru.

    How many grounds are there to that engine, are the stators known to fail, etc. The ski ran fine when put away and first time pulling it out this season this is the scenario.

    New battery, all *looks* good inside the hull, etc.


  2. #2
    Master of the Dooniverse
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    Update #1

    Cleaned the battery connections, which were a bit dirty and had light corrosion. No change.

    Disconnected the temp sensor, no change

    Removed the plug wires and plugs and reinstalled, fired over and ran perfectly. Shut it down, removed the plug caps and upon reinstall the boat limited again

    Pulled the caps off, suqeezed them a touch to tighten, reinstalled and the boat fired up and ran perfectly.

    Pulled the caps again to verify and again the ski would limit.

    Installed new spark plug caps and boat fired right up, then again after removing the wires it won't fire. I have good connections at the plug caps, so I don't think that or the wires are the issue. I'm pretty annoyed now. I let the ski sit whiel I checked a few things and had the kill switch disassembled to see if perhaps there was an issue inside it, which there wasn't.

    Refired the ski, and it ran perfectly, then after revving a bit, it began again to limit and wouldn't go over 4k or so.

    Now I just don't know what could be going on. Seems everything is good and tight, I've never had an intermittent issue like this that goes away and comes back. I had myself convinced it was the plug caps, but they are good and tight and the coils ohm out perfectly, so I'm just lost.

    Any suggestions?

    Oh, and it's a 1996 SLT 780, not a 750. That's what the side says anyhow. Ebox was clean as a whistle inside and no connections had any corrosions whatsoever. everything was nice and tight.

  3. #3
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    When you installed new spark plug boots, did you trim the spark plug lead about a quarter inch back? They tend to get corroded over time and not make a good connection. Ended up being the problem with my '96 SL780 when it wouldn't rev.

  4. #4
    Master of the Dooniverse
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    Update #2

    Thanks hyoctane, yes I did. did the whoel typical spark plug deal, trimmed back and reinstalled, threading in the screw part. The connections are solid.


    Update #2:

    OK, now I feel I'm making some headway.

    Browsing the helpful tech threads here on the polaris models, I tried to reset the MFD, since it seems there is some sort of sensor error or failure(s) that can make the thing limit.

    Here's what happened.

    I went back outside after 20 minutes and fired it up. Boat ran perfectly. Shut it down, fired back up and it was rev limiting. (Seems it wasn't the plug wires or that was only part of it).

    I held the mode and set buttons for 5 seconds til the CAL screen came up on the MFD. Hit set and it returned to normal and the blinking light went off. At that point, I refired and it ran perfectly. Shut it off and restarted only to rev limit.

    I've repeated this sequence now 4 times, so I am sure it is something along the line of a sensor or the MFD itself that is causing the issue. This particular ski has a failed fuel baffle, such that it reads empty all the time. I've never owned a machine that rev limited on low fuel, but maybe this SLT does?

    I had disconnected the fuel baffle from the Ebox as well as the temp sensor, but that had no change. I'm wondering if the MFD sends a signal to the CDI and once it's "limiting", it won't stop until there's a reset or something???

    I feer I'm close to a solution, but I know that someone must have experienced this before, so I'm hoping for a chime in to either tell me I'm an idiot or tell me I'm right and here's the sequence to unfukk this machine, lol.

    Wayne

  5. #5
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    Edit: I need to double check on something...

    Have you tried just disconnecting the MFD and running it then?

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    The 780 does rev limit, or go into "limp mode" from low fuel

    Try disconnecting the grey wire from the elec board and see if that helps.

    If it does, replace the fuel float and reinstall the grey wire.

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