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  1. #1

    More '94 SL650 Cooling Questions

    Hello All,

    I am in the process of restoring my 1994 SL650. In the middle of working thru all the needed fuel related tasks, the last 3 brittle strands of wire finally broke off the Thermo Switch (in the upper Water Outlet Manifold) that leads back to the “Brain Box” so now I must do something about that too.
    I must say that I’m less than impressed with a warning system that consists simply of a buzzer that may, or may not, sound off if I’m overheating. So I have a few questions for you all if you have the time.

    I was wondering about eliminating the “Buzzer” system and putting an aftermarket Temp Gauge in the dash next to the Fuel gauge but I’m not exactly sure how to do it. Most importantly should I do it at all? Would you consider doing it to your ski? and if so, Where would I correctly monitor the engine temp from? ………. would I screw the new temperature sender into the upper Water Outlet Manifold where the old Thermo Switch was? Or would I screw it in over on the Exhaust Pipe where the Temp Switch is? Also, does anyone know if the new Temp Gauge would always draw power from my battery since there seems to be no “off” in the system which isolates the battery. Should I wire it direct to the battery and put and interrupt switch in the line to protect the battery charge when not in use? Or is there a 12v wire that only gets “Hot” when the ski is running that I could tap into which could supply the gauge a small bit of power without overloading that circuit?

    I read, somewhere in these forums, a reference to completely removing the thermostat. Is this a viable option for my ski. I must admit I like the idea of eliminating as many possible future-overheating possibilities as I can. Do I run the risk of actually running my engine “Too Cold” if I do this?

    Again, thank you in advance for taking the time to read this,

    Jeff Galloway

  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Jul 2007
    near Toronto, Canada
    The overheat warning system in your model is the simplest version Polaris did. The sender is a simple switch that closes when it gets too hot. No power draw when the engine is not running.

    You can upgrade the LR voltage regulator module to one that also has an Orange wire. The Orange wire provides switched power only when the engine is running.

    None of the Polaris carburetor 2-stroke engines, even the most modern versions, has a temperature gauge. In all cases the temp sender is a simple switch that closes when temp gets too hot (about 160F). The newer models have a red flashing lamp and a warning message, while yours has a buzzer.

    While many owners have indeed removed the thermostat, it partially depends on how cold the water is where you ride, and how you ride the machine. The thermostat helps keep the engine at proper operating temperatures when running at LOW speeds.

    There is a spring loaded pressure bypass valve in the thermostat housing that opens up when the engine RPM rises and allows water to flow regardless of thermostat temp. Thermostat is set to open at about 140F.

    This system keeps the engine warm at lows speeds, and when you speed up the cooling flow increases to match engine power.

    Have a look at how the newer model years are configured.

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