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  1. #1
    TyCast's Avatar
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    Exclamation 1993 Polaris SL 650 Overheating Issue

    i believe I have finally found out the issue I have been having for a long time.

    In a previous thread, i had the issue of erratic bogging, which it would accelerate then deaccelerate over and over, erratically.

    Well, i just changed out my old faulty carb for a good running used one (which sucked cause the nuts stripped and i had to Dremel them off).

    So i fixed the carb issue which prevented the front cylinder from working. But the old issue remains, the erratic bogging.

    So after 25Mins or so of running at near top speed, it does this erratic bogging. I check the cylinders while floating in the water with my hand and theyburn my fingers. I assume its supposed to be real warm, not hot to the touch (correct me if im wrong). It works fine until that 25min mark.

    I think it could be one of two things. One, the pistons arent getting enough oil, or two, theres some issue in the cooling assembly.

    What do you guys think?


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    The 1992 and 1993 Polaris Fuji engines have a different cooling system than later model years. If your 1993 SL 650 is still in the original factory configuration there is water cooling running through the crankcase water jacket as well as the cylinders, heads and the exhaust manifold water jackets.

    It sounds like your engine has problems with cooling water flow. You need to investigate the entire cooling system. Look for kinked hoses, incorrectly connected hoses, clogs, etc. all the way from the plastic inlet mesh screen inside the jet pump exit nozzle, through the water tube, all the way to the water exit out of the hull. Open everything and look inside.

    Tip: Take photos before you begin disconnecting hoses. And make a diagram so you can put it back together afterwards.

    These engines sometimes accumulate sand and silt inside the water jackets. If you see any signs of sand inside the cooling water connections at the engine or in the thermostat housing, you may need to tear down the engine to fully investigate. The sand can get packed into the water jackets and needs to be mechanically dug out water flushing will not do it.

    This is a fairly involved process so the engine is best removed from the hull. A set of new engine gaskets will be needed.

  3. #3
    TyCast's Avatar
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    Luckily, my ski has never been to the beach, so no sand issue. Taking out the enigne would be a nightmere. Taking out the carbs was a nightmere.

    So, as for the slow overheating, could that be an not enough 2-Stroke oil issue or just an issue in the water cooling system? I mean, it takes about 20-25 mins to reach overheating. I would assume if it was the cooling, it would overheat much quicker.
    Last edited by TyCast; 08-06-2014 at 04:11 PM. Reason: forgot the goodz

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by TyCast View Post
    Luckily, my ski has never been to the beach, so no sand issue. Taking out the engine would be a nightmere. Taking out the carbs was a nightmare.

    So, as for the slow overheating, could that be an not enough 2-Stroke oil issue or just an issue in the water cooling system? I mean, it takes about 20-25 mins to reach overheating. I would assume if it was the cooling, it would overheat much quicker.
    Generally speaking lack of oil will result in rapid wear of the piston rings and cylinder walls. The engine will have a short lifespan if there is not enough oil.

    Does this engine still have the factory oil injection system? Has it been checked over and serviced? New oil filter?

    The fact that it gets too hot to touch tells me the cooling system is not working properly. Until the cooling system is gone through and the problems found and fixed, there is no easy work around.

    Your 1993 machine is now twenty one years old. Who knows what has happened to it in the past. Do not assume it was working properly before you got it, or even before the guy before you got it.

    As noted in my signature links, the only way to have a reliable older PWC is to make it reliable yourself. That means doing the work up front. Almost everything needs to be at least inspected, and lots of things will need maintenance, servicing, updates and internal cleaning.

    Removing the engine may seem scary, at least the first time. If you view this as an opportunity to learn how these things work and how to work on them, then it offers a lot of potential.

  5. #5
    BlueFishCrisis's Avatar
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    I would classify my Fujis at operating temperature as hot to the touch, as opposed to real warm, and it gets there after 1 high speed pass, not 25 minutes. I can touch the cylinder tops, but not for more than a few seconds before it gets uncomfortable. The Thermostat operates in the 140-150 degree range. Get an infrared thermometer from Home Depot or Harbor Freight for around $30 to verify.

    Also, your ski does have an overheat sensor connected to the water rail. Verify that your overheat buzzer (located under the handlebar pad) is operating properly. If it is, and it is not sounding, than I would think the bogging is likely caused by something else.

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