61X 701 with girdled head (heat and cooling)
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  1. #1
    PWCToday.com Is My Home Away From Home JSNate's Avatar
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    61X 701 with girdled head (heat and cooling)

    I upgraded my daughters ski from a 61X (stock) that had a B-Pipe with Mod chamber, single cooling and a Jet Works flow unit in the stinger line. The ski ran well and engine temp was what I consider normal.

    Upgraded to a Blowsion One Piece Girdled head with 37cc domes, compression at 170 PSI. I ran the water lines as they were before the head change. Single cooling, stinger retained the Jet Works in the stinger line and put a T to join both exit lines from the head. Ran the water from head to lower pipe as it was before. I also tried blocking the one line from the head to see if that changed anything. It did not.

    The cylinder and head is hot.. And by hot, I mean after five minutes of running normally, I can't touch it for more than a couple of seconds. I've had this amount of compression on several other skis with no issue. So... Wondering if anyone has had similar results?


    Does anyone think the Jet Works stinger restriction could be slowing water flow enough to cause excessive heat in the engine?

    Thanks for your feedback!

    Nate
    Last edited by JSNate; 09-16-2018 at 07:52 AM.

  2. #2
    Resident Guru JC-SuperJet's Avatar
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    Re: 61X 701 with girdled head (heat and cooling)

    Try this cooling routing:

    Single Cooling Supply Line to Bottom of Exhaust manifold (standard obviously)

    Rear Cylinder Head to Bottom of Head pipe (no splits or tees)

    Block the Front Cylinder Head Outlet with Brass plug, Rubber Cap or Flush Kit.

    Front of Head Pipe to Pisser and Stinger with a Tee. Drop Leg of Tee should go to Stinger.

    So only one Pisser Bypass is needed.

    Also make sure the Flow Control Valve is not clogged.

    Rule of Thumb: One Cooling Line ====> One Pisser Bypass

    There is some discussion of minimum cooling water dwell time inside the Block in order for good heat transfer (cooling) from the Block & Head to the Cooling Water to occur.

    Remember that the Cooling Water is "dirty", meaning it is aerated, full of air bubbles and silt. Air Bubbles and Silt don't help cooling.
    Last edited by JC-SuperJet; 09-16-2018 at 10:10 AM.

  3. #3
    Resident Guru JC-SuperJet's Avatar
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    Re: 61X 701 with girdled head (heat and cooling)

    Also do a Compression check to double-check against the nominal 37cc Dome size = 170psi.

    It's possible for a set of Domes to be mis-labeled...

  4. #4
    PWCToday.com Is My Home Away From Home JSNate's Avatar
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    Re: 61X 701 with girdled head (heat and cooling)

    Thank you for the feedback, JC. I will check compression and make certain the lines are clear. I gave thought to dwell time as well.. Years ago, I had a JS 550 with dual cooling lines that would get hot and seize. Omitted one of the cooling lines and problem solved. Clearly the water was not staying in that engine long enough to dissipate heat.

    I plan to update with my results.

    Nate

  5. #5
    PWCToday.com Is My Home Away From Home JSNate's Avatar
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    Re: 61X 701 with girdled head (heat and cooling)

    Compression is 178 ish PSI and I ended up removing the Jet Works restrictor in the stinger line. Allowed both water outlets from the head to flow into a T, and then to the lower fitting on the B Pipe head pipe. Jumping 28 PSI with this Blowison head did exactly what I expected regarding performance. Gave the ski a nice hit and excellent pull.. She feels a bit rich on the low end, but I can tune that out.

    Thanks again for the input, JC. Much appreciated.

    Nate

  6. #6
    Resident Guru JC-SuperJet's Avatar
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    Re: 61X 701 with girdled head (heat and cooling)

    Right on Nate!

  7. #7
    PWCToday.com Is My Home Away From Home JSNate's Avatar
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    Re: 61X 701 with girdled head (heat and cooling)

    Put the ski on the trailer, tied her down and water tuned the ski from my beach.. I was able to keep on eye on the heat and tune the carb under power. Took her out for an hour of hard riding, and she runs perfectly!!

    Nothing quite like adding compression to enhance the B Pipe.. Nice combination tossing all that torque at 155 millimeters of pump!
    Last edited by JSNate; 09-17-2018 at 07:39 PM.

  8. #8
    Resident Guru JC-SuperJet's Avatar
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    Re: 61X 701 with girdled head (heat and cooling)

    Amazing how the cooling water hose routing can make or break a two-stroke engine's performance.

    Now we're having fun!

    I can just visualize that SuperJet jumping out of the water with that big pump...
    Last edited by JC-SuperJet; 09-17-2018 at 08:55 PM.

  9. #9
    PWCToday.com Is My Home Away From Home JSNate's Avatar
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    Re: 61X 701 with girdled head (heat and cooling)

    Thanks, JC! The Air Blair's are custom made hulls, hand molded in Michigan by Adam Blair. He makes a few models.. Dart, Fixxie, Air and hybrids of each. Light, short, wide and tough as nails. The skis are made primarily for surf riding and the ensuing abuse encountered in the surf. My two skis are Darts, and they are great machines that can do it all.


    **That is Adam Blair inverted on a "Fixxie". The builder can ride like no other!
    Last edited by JSNate; 09-18-2018 at 06:42 AM.

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