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  1. #1

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    96 SLT 780 help. Motor wont rev past 4000

    Hey Guys just want to run a problem past ya to see who might know the answer to it. I have an old 96 SLT 780 triple with a Fuji in it.
    Now it doesn't want to rev out on the trailer. (havent put it in the water yet because of this)
    It seems like there is a rev limiter coming on, It seems to limit itself around the 3-4000 rpm area. I put fresh gas in it. Cleaned out the Fuel Pump and rebuilt all 3 carbs. Compression is 140 each Cyl. Reeds are perfect.
    It actually surges a little too when you hold it wide open. It feels like its real real rich and it smokes (oil) like a dog too with it held wide open.But just wont rev past about the 3-4k mark. There is plenty of fuel going through the high speed circuit as I can see it coming through the bombshell
    The gauges are all misted up and appear to not work either.

    Oil is 3/4 full and gas 1/3 full.
    Maybe one of you polaris Guru's can nail it on the head straight away.I was thinking something electrical is causing this. It is not mis-firing at all.
    Any suggestions please???????????
    Thanks


  2. #2
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    You can test if its in limp mode by disconnecting the grey wire from the board from the cdi. Is the red light flashing on the mfd?
    I wouldn't recommend running high revs on the trailer.

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    How do you know what revs you are reaching if the MFD is not displaying clearly?

  4. #4

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    Quote Originally Posted by K447 View Post
    How do you know what revs you are reaching if the MFD is not displaying clearly?
    I can tell from the sound from the engine . And I have a tacho , do you?
    Where were you going with that question?

    I will disconnect the gray rev limiter wire tomorrow and test that.
    I have heard reports that the fuel float if jammed effects the rev limiter and does the oil if low. Still Curious to see if some Mechanic out there can pin point it saving me hours of diagnostic work.

  5. #5

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    Quote Originally Posted by starflight View Post
    You can test if its in limp mode by disconnecting the grey wire from the board from the cdi. Is the red light flashing on the mfd?
    I wouldn't recommend running high revs on the trailer.
    Red light doesn't come on. Maybe its because the whole MFD doesn't work

  6. #6
    axgrider73's Avatar
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    Quote Originally Posted by nz253 View Post
    Still Curious to see if some Mechanic out there can pin point it saving me hours of diagnostic work.
    Well, unless there is a lucky guess, thats not going to happen. There is multiple causes for a problem like yours so it will take some eliminating to properly diagnose the cause.

    On My '02 Virage, the ski will go into limp mode if the MFD goes blank. So, I say that unhooking the gray wire from the CDI would be the place to start.

    Let us know how it goes.

  7. #7
    Moderator beerdart's Avatar
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    Hey nz Welcome to the hulk.

    On the 780 they will limit the RPM for over heat and low Fuel. I would have to say you have a fuel logged float that is not uncommon on Polaris. A new one can be found here. If you do want want to fix the gauge install a 220 ohm resister in place of the fuel sender. http://www.watcon.com/Catalog_Pages/...Update_Kit.htm

    The factory manual can be found here.
    http://www.greenhulk.net/forums/showthread.php?t=38870
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  8. #8

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    Top work beerdart. your the guy I was looking for. I think I'll locate the 220 ohm resistor and put it in place as the MFD dont work. I might pull that Grey wire just to see if it disables the limiter first.. I'll keep you guys posted as to how I get on. Cheers

  9. #9
    Moderator beerdart's Avatar
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    The MFD might be a blown 1/4 amp fuse in the box take a peek while its open.

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by nz253 View Post
    I can tell from the sound from the engine . And I have a tacho , do you?
    Where were you going with that question?
    It has happened in the past that the MFD display was only partially working (some LCD numeric segments staying blank), and it was 'showing' RPM below the actual revs.

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