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Help ZXR/Balius - Running without the thermostat

Discussion in 'Kawasaki 250cc In-line 4's' started by jack_lee, Feb 25, 2023.

  1. jack_lee

    jack_lee Active Member

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    I'm running into a problem recently, where my thermostat jammed. Does anyone here run without the thermostat in their ZXR/Balius?
     
    jack_lee, Feb 25, 2023
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  2. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Generally speaking, running without a thermostat is doable, BUT the thermostat in addition to allowing the water to reach the operating temperature also restricts flow somewhat so that the water doesn't cavitate and has sufficient time in contact with the hot metal to absorb heat and take it to the radiator, where it needs to be moving at the correct speed to dissipate the heat it's absorbed.

    You could continue to do it until you get a replacement
     
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    ruckusman, Feb 25, 2023
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  3. yak_attak

    yak_attak Active Member Premium Member

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    Hi Jack, it's Jack here.

    I know a motorcycle wrecker here in NZ and could ask about sourcing a thermostat for you if you would like. Let me know and I'm happy to cover the postage to Malaysia.

    Chairs
     
    yak_attak, Feb 25, 2023
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  4. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Part number is 49054-1066 for an early Balius, the ZR250 was manufactured up to 2007 in Japan

    Cost is about $35 USD from megazip
     
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    Linkin, Feb 25, 2023
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  5. DannoXYZ

    DannoXYZ Well-Known Member

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    Depending upon ambient temperatures, running without thermostat is bad idea. This would prevent engine from running at proper temperatures. Oil should be above 100C to boil of all water that condenses inside crankcase. Without that, your oil's lubrication properties are compromised and increased wear is result. And since engine parts aren't up to operating temp, they don't fit and mesh properly, also leading to increased wear and less power.
     
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    DannoXYZ, Feb 26, 2023
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  6. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    As a temporary measure (until you get a replacement), you could drill a hole or two in the existing thermostat so that water flow is restricted enough to heat up, but still flows around the engine.
     
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    Frankster, Feb 26, 2023
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  7. jack_lee

    jack_lee Active Member

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    Actually, I've tried to run it without the thermostat. The bike still get overheated after about 20min of riding. There water overflows to the reservoir & the are air pockets inside. Just like you said, the water does not have sufficient time to cool down in the radiator before going into the engine. The worst is I could have cooked the head gasket at the earlier event.
     
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    jack_lee, Feb 28, 2023
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  8. jack_lee

    jack_lee Active Member

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    Thanks for the helps man. I've found a used thermostat(with its housing) from a EL250. Will give it a try when it arrived.
     
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    jack_lee, Feb 28, 2023
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  9. jack_lee

    jack_lee Active Member

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    I should have tried this before totally removing the thermostat. As I noticed from the radiator cap inlet(before it gets hotter), the water just runs through the radiator at a face pace. The manual said that the thermostat only opens 3mm when the water temperature reaches 85°. But the whole cooling system is already at 50° just letting the engine idle for about 5 minutes. So there is nothing could cool down the engine faster when it reaches its operating temperature.

    I'm just worried that i've cooked the head gasket.
     
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    jack_lee, Feb 28, 2023
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  10. thebeefsalad

    thebeefsalad Well-Known Member

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    Exhaust gas tester is free to rent at parts houses here, just have to pay for the fluid ($25, enough for 2 tests) Have you ran the engine with the rad cap off to see if its burping as into the cooling system, and checked for a milkshake in the oil?
     
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    thebeefsalad, Feb 28, 2023
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  11. jack_lee

    jack_lee Active Member

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    ya. No burping from the cap mouth and no milkshake in the oil. Does all head gasket burn cases cause a milkshake in the oil?
     
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    jack_lee, Feb 28, 2023
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  12. thebeefsalad

    thebeefsalad Well-Known Member

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    No.
    You can mix combustion gasses and oil, combustion gasses and coolant, and oil/coolant depending on where the leak develops. Leakdown test is probably the cheapest/easiest now that I think about it.
     
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    thebeefsalad, Feb 28, 2023
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  13. jack_lee

    jack_lee Active Member

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    Copied that. I will replace the thermostat first. If the situation persists, i'll get the exhaust gas tester to check. thx!
     
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    jack_lee, Feb 28, 2023
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  14. DannoXYZ

    DannoXYZ Well-Known Member

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    What's gauge say when water is overflowing into resevoir? Have you checked temperature of radiator by inlet port with IR thermometer?

    This really appear just to be weak and worn-out radiator cap. Test it to determine what pressure opens it.

    [​IMG]
     
    DannoXYZ, Sep 20, 2023
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