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Thread: 750 Overheat

  1. #1
    I transcend race Hombre! TBone14's Avatar
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    750 Overheat

    I helped a buddy of mine rebuild a '95 SLT750 - rebuilt carbs - replaced holed piston.

    Took it out for a shakedown run yesterday....ran great for a couple of minutes then then HOT warning came on and engine shut down....I swam it back into shore and got it out of the water. Turns out, he left the cooling supply line off of the exhaust and it was just pumping into the hull.

    I think I read on here that 750's don't have limp mode....do they shut down the engine if it overheats? After we let it cool down, it turned over and started. Obviously, we are going to comp test today, but what are the chances that it is toast? I feel horrible, because I should have double checked all his stuff for him....we even started on trailer etc...and didn't see anything wrong.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    As far as I know none of the Polaris 2-stroke engines will purposely shut themselves down under any condition. The most the electrical system will do is enforce an RPM limit, even if it is overheating, out of fuel and oil, taking on water, upside down and on fire

    If it stops while riding then the cause is mechanical, such as hot piston seize.

    Tip: This is why the first stages of 'water testing' should happen with the seat off, strapped to the trailer in the water at the launch ramp. Then you can run it long enough to confirm it is not overheating and there are no significant water leaks or hose issues.

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    I transcend race Hombre! TBone14's Avatar
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    Quote Originally Posted by K447 View Post
    As far as I know none of the Polaris 2-stroke engines will purposely shut themselves down under any condition. The most the electrical system will do is enforce an RPM limit, even if it is overheating, out of fuel and oil, taking on water, upside down and on fire

    If it stops while riding then the cause is mechanical, such as hot piston seize.

    Tip: This is why the first stages of 'water testing' should happen with the seat off, strapped to the trailer in the water at the launch ramp. Then you can run it long enough to confirm it is not overheating and there are no significant water leaks or hose issues.

    Did that...I guess not long enough, because neither of us noticed anything.

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    BlueFishCrisis's Avatar
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    Quote Originally Posted by TBone14 View Post
    Did that...I guess not long enough, because neither of us noticed anything.
    Then perhaps the hose was on, and not clamped tight.... I have had hoses that will stay on under idle conditions but blow off when higher pressures are introduced at higher RPM. I would think that if you caught the overheat as soon as it happened, and you did the right thing (by getting a workout swimming), hopefully all should be ok....

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    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by TBone14 View Post
    Did that...I guess not long enough, because neither of us noticed anything.
    Did you apply heavy throttle and hold it for at least a few seconds?

    I might run my own on the trailer at the ramp for several minutes. The longer the better, as sometimes while I am watching it run on the ramp I remember something else that I should check or do.

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    BlueFishCrisis's Avatar
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    Like put the plug in

  7. #7
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
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    I'm betting the ski died from sucking some water into the intake. Doesn't take alot to stall a motor. Hope thats the case.

  8. #8
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Prob seized from heat. Hopefully you are running the 32:1 break in ratio and the extra oil prevented much damage from occuring. Comp test might help. But if the rings haven't seated yet, your reading will still be low. So don't panic yet.

    If comp is low, remove the head and get a better look at what is going on. If no major scarring has occurred, the rings may still need to be broke in.

  9. #9
    I transcend race Hombre! TBone14's Avatar
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    110 - 110 - 110 cold

    I think it'll be alright - was 120 on all three prior to the problem

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