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  1. #1

    SLX 780 running hot on PTO

    What could cause just the PTO to run hot. On the trailer (in the water) it was getting too hot to touch when idling for only a minute or so. We also noticed that after you'd run it and kill the engine, exhaust smoke would continue to escape back through the PTO carb for several minutes. It did not come out of the other two carbs.

    Another observation - looking at the water bar, the hole for the PTO was much smaller than the other two. Was there an update or anything to open up this hole more and get some more water flowing through it?

    My first though is a bad reed, but I don't know if this would cause a lean/hot situation. Looking through old threads on here, I'd also consider:
    -Running lean - I checked the screws and even reset them
    -Sucking air - bad rear crank seal?

    What say the Hulk?


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Smoke coming up from the PTO carb after engine shut down? Check the PTO reeds.

    Also check crank index.

  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    That's an odd one.....

    There's a 3/8" fitting that comes off the exh manifold that is plumbed to the "T" in the incoming water supply. Make sure that fitting, "T", and hose are clear and unobstructed.

    Also make sure the thermostat is working properly. Check to see cooling water is actually exiting the engine.

    Check the waterbar (blow through it to be sure it's not obstructed) and the PTO head for restriction.

    You may have got an "air pocket" trapped in the cooling system that needed to work itself out. (which would be a first for me)


    If the ski was still in the water when you saw the "smoke" coming out the carb top, that's normal. Waves tend to force air back through the exhaust pipe and out the 1 cyl that's exhaust port is open.

    Reeds don't seal 100%, so that's the "smoke" you're seeing. Actually, it's not ucommon to hear your reeds whistle when this happens. The petals flutter as the air pushes past them creating the sound.

  4. #4
    We pulled the water bar and ran it for a few seconds to verify water was flowing....it gushed out out of the heads on all 3 cylinders quickly. I don't think it's a blockage problem.

    What about the size of the holes in the water bar? Was is the PTO so much smaller than the other two? I would think the smaller hole would restrict water flow and make that cylinder hotter.


    I'm pretty sure it does still have a thermostat. We didn't have an allen wrench at the lake to pop the housing out..gonna have to get it later...but that still shouldn't make only one cylinder overheat.

  5. #5
    cigarlust's Avatar
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    Hey Brian, I was jacking around on Ebay and found a pic of a 96 slx water bar, it looks like the pto hole is smaller?
    Click image for larger version. 

Name:	cooling bar.png 
Views:	134 
Size:	399.6 KB 
ID:	235927 Just like mine...



    I also need to buy a 780 head off someone, looks like it had grenaded at some point in its life, the PTO dome is the one I'm after

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by bgaidan View Post
    ... What about the size of the holes in the water bar? Why is the PTO so much smaller than the other two? I would think the smaller hole would restrict water flow and make that cylinder hotter.

    thermostat ... that still shouldn't make only one cylinder overheat.
    Polaris had a reason for making one hole smaller, and when running properly the stock machines do not have an overheat problem.

    Perhaps there is sand/silt or something else in the water jacket restricting flow to one cylinder.

    Do check crank index, and it would be good to know the reeds were not damaged.

  7. #7
    thester71's Avatar
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    Are you positive the head gasket is oriented properly?

  8. #8
    Nope!

  9. #9
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by bgaidan View Post
    We pulled the water bar and ran it for a few seconds to verify water was flowing....it gushed out out of the heads on all 3 cylinders quickly. I don't think it's a blockage problem.

    What about the size of the holes in the water bar? Was is the PTO so much smaller than the other two? I would think the smaller hole would restrict water flow and make that cylinder hotter.


    I'm pretty sure it does still have a thermostat. We didn't have an allen wrench at the lake to pop the housing out..gonna have to get it later...but that still shouldn't make only one cylinder overheat.
    Ok, but is there a blockage in the water bar?

    The PTO hole is smaller in the water bar to keep water from just flowing up and out since that's where the exit is. By restricting it, it now feeds more water to the MAG which needs the most coolant of all 3.

    You are correct about the thermostat, but if you're having cooling issues, might as well check the thermostat since you're there anyway.



    Quote Originally Posted by thester71 View Post
    Are you positive the head gasket is oriented properly?
    Great response.

    Where did you situate the head gasket's '"shark fin"? Should be positioned under the cooling bar mount

    And did you make sure you had the right side up? It's labeled "up" or the number 78 is stamped into it and must be positioned correctly.

  10. #10
    Quote Originally Posted by K447 View Post
    Polaris had a reason for making one hole smaller, and when running properly the stock machines do not have an overheat problem.

    Polaris has also been known to screw up and make revisions and corrections to parts in later years and previous owners have also been known to put the wrong replacement part on. I learned this with my Genesis which had burnt down at least 2 MAG pistons because it had the wrong water bar installed on it.

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