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  1. #1
    Inssomniak's Avatar
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    780 Bogs bad (trailer)

    I just acquired a SLT780, overall pretty rough, but complete, don't know all the history.

    Starts and runs, but bogs and wont rev high at all., I can see fuel just getting dumped into all the cylinders by looking down the carbs. Good 130+ compression on all cylinders, good spark on all 3.

    After running and trying to get to rev up for 20 seconds, plugs and cylinders are soaked in fuel.
    I don't have a timing light to check timing. Mag cylinder is the only one that really gets warm after 20 second run on trailer. Piston wash looks rich across the board, worst on MAG (totally black)

    No history on carbs, no nothing..


  2. #2

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    Clean carbs - minamum and use genuine Mikuni kits with needle and seat . You will need a new intake gasket as well .

  3. #3
    Inssomniak's Avatar
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    I just pulled the inspection cap off, and found the timing marks, there are 2 sets, 2 small dashes, with a large dash in the middle.

    EDIT:

    When mag is at TDC, the timing marks are not even close, its off probably 3/4 of an inch from any of the marks on the flywheel.
    I think the key is sheared.

    (Ill also take a link to the service manual for this engine if anyone has it)

    Thanks
    Last edited by Inssomniak; 03-29-2017 at 04:11 PM.

  4. #4

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    Find Bluefish - he is all knowledgable

  5. #5
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    First and foremost....read this entire website:

    http://polarispwcknowledge.shorturl....t-things-to-do

    I agree that you need a carb rebuild at a minimum. If you're seeing fuel leak into the throats, you definitely have an issue going on there. More than likely you have a stuck needle and seat allowing fuel to dump into your engine. If you are not careful, you could potentially hydro-lock your engine with fuel.

    Timing could be an issue if your flywheel sheared the woodruff key but I think you need to start with the basics...get your fuel system up to par since it has been probably sitting then worry about timing if it still isn't running correctly.
    Last edited by K447; 03-29-2017 at 09:25 PM. Reason: http://polarispwcknowledge.shorturl.com/first-things-to-do

  6. #6
    Inssomniak's Avatar
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    Fuel doesnt leak in, it seems to spray nicely and evenly out the main jets in all 3 carbs when the throttle is pressed., no lack of fuel when revving is attempted, Just doesnt rev up much past idle, and the exhaust is dripping wet with oil its dripping out the through hull, so I suspect its been doing this for a while.

    I just want to know, what I should see on the flywheel, with the MAG at TDC? It sure is off an inch, from any marks.

  7. #7

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    As mentioned above - start reading and its not too difficult- this forum on the Polaris has had a very very comprehensive group of individuals share all of their experience and well documented - as stated earlier start reading and enjoy their efforts in making it simple

  8. #8
    Inssomniak's Avatar
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    Where is a good place and price, to get the genuine kits? There are tons on eBay, and SBT even carries it, but is it good enough?

  9. +1 by:


  10. #9
    BlueFishCrisis's Avatar
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    Kits will be $50 plus per carb, so expect to pay $150 to $175. Get only Genuine Mikuni parts.

    Not revving up past idle tells me its time to check timing and/or ohm out your stator. Even if the stator Ohms out OK, it may be bad. Also check the limiter on the CDI by removing the grey wire from the circuit board. You could be experiencing a limiter effect. Hyoctan23 provided the link for the info you need......

  11. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    First, before you buy anything.....

    With the engine running, pull 1 spark plug wire at a time. (be careful to not get shocked)

    If the engine does not drop RPM, that cylinder is not firing.

    Make sure all 3 cylinders are running.


    What I find most is people tend to suck up water in the engine (hydrolock) and put the ski up because something is wrong.

    If that is/was the case, your crank phase may be off.

    Or you may have a bad reed or reeds.

    Lastly, is the orange plastic ring in the fuel/water seperator floating? If so, you have water inside the fuel

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