650SX Overheating, Should It Need Dual Cooling?
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  1. #1
    Frequent Poster joshuabbrown's Avatar
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    650SX Overheating, Should It Need Dual Cooling?

    Ive got a 650SX that ive had tons of trouble with. Recent issue is that it kept popping head gaskets. After decking both head and cylinder, plus a fiber gasket, still popped. Swapped in a spare stock motor with 130psi. Swapped over the bigger carb and coffman pipe. Also has a mariner waterbox if that matters. I didnt think you needed dual cooling till you started getting to 180s compression, but my motor is sure overheating. After riding, it has a solid sizzle with the water test on the head and cylinders, fine on the pipe. It runs amazing and is super peppy, is it possible it is too lean maybe in the top end so that is causing the overheating? I can run dual cooling, but I didnt think it was really necessary and want to make sure I have the root of the issue before I kill another motor.

    The lines are run from the stock water inlet, to the ex manifold, out the head to the front of the ex pipe, out the rear of the ex pipe to the pisser and stinger. I believe this is standard routing. The line laying on the carb is the stock water exit, that I am going to use if I have to dual cool.

    Last edited by joshuabbrown; 08-26-2021 at 10:36 AM.
    Anyone in South GA, (Vidalia) lets ride.

    The Fleet:
    1990 650sx (minty fresh)
    1991 650sx all the aftermarket bolt on stuff
    1990 TS (The water moped)
    1986 JS550
    1991 Square Nose 650 SJ
    90something Blaster 2
    Somehow they all run, for now.

  2. #2
    PWCToday.com Is My Home Away From Home
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    Re: 650SX Overheating, Should It Need Dual Cooling?

    drill out all your npt fittings for more water flow. Might also need to buy new npt fittings that have a larger ID. And check the pump and water line. Could be broken or cracked and not flowing the full amount.
    triceps are the biceps of the back of your arm.

  3. #3
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    Re: 650SX Overheating, Should It Need Dual Cooling?

    Is it possible that you are missing the gasket between the exhaust manifold and head pipe or that the gasket you used has bypass holes in it?
    If that gasket is missing or has holes in it, the water will bypass the engine and go straight from the exhaust manifold and into the head pipe. I ask this because you said your exhaust is cool but the engine is hot. In a normal set up like you have, the only way for water to get to the exhaust is through the engine. If that gasket is missing or has holes it will do what you are describing.

  4. #4
    Frequent Poster joshuabbrown's Avatar
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    Re: 650SX Overheating, Should It Need Dual Cooling?

    Thanks for the quick replies. I will try drilling out the fittings, that should be easy to test. Do I drill out just the pump fitting or the fitting in the head and pipe as well? Do you know the max drill size?

    I just swapped the pipe over from the other blown engine, so the exhaust gasket should be good. But I will pull it back off and check, Im only human and could have made a mistake assembling.
    Anyone in South GA, (Vidalia) lets ride.

    The Fleet:
    1990 650sx (minty fresh)
    1991 650sx all the aftermarket bolt on stuff
    1990 TS (The water moped)
    1986 JS550
    1991 Square Nose 650 SJ
    90something Blaster 2
    Somehow they all run, for now.

  5. #5
    Frequent Poster joshuabbrown's Avatar
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    Re: 650SX Overheating, Should It Need Dual Cooling?

    So to close this thread, chock one more up to exhaust gasket. Found my gasket had a little flap blown out. Probably what killed my last motor. Thats what I get for reusing exhaust gaskets.
    Anyone in South GA, (Vidalia) lets ride.

    The Fleet:
    1990 650sx (minty fresh)
    1991 650sx all the aftermarket bolt on stuff
    1990 TS (The water moped)
    1986 JS550
    1991 Square Nose 650 SJ
    90something Blaster 2
    Somehow they all run, for now.

  6. #6
    PWCToday.com Is My Home Away From Home Cleatusjo's Avatar
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    Re: 650SX Overheating, Should It Need Dual Cooling?

    Yikes
    '94 Kawi TS 650
    2002 Kawi STX-R 1200
    too much to list

  7. #7
    Top Dog JC-SuperJet's Avatar
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    Re: 650SX Overheating, Should It Need Dual Cooling?

    Yep, you saved a lot of money reusing Gaskets...Lesson learned and never forgotten now.

    Metal Gaskets can be reused IF in good condition.

    Another Rule is to ALWAYS use Genuine Made in Japan Mikuni Carb Kits. Don't fall for the cheap made in China knock-offs!
    Last edited by JC-SuperJet; 08-27-2021 at 11:53 PM.

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