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  1. #1
    PWCToday Newbie Corndog69's Avatar
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    1998 750SXI Pro POP-off question

    Hello all. I know this has been a well discussed topic but I was hoping to get some feedback in a single thread for my application.

    Rebuilding Ng stock block with new kit but did buy ADA head to get 180psi compression to stay with high octane fuel. Bought used Factory limited pipe and aftermarket k&n filters and new boyessen reeds. Other than those mods, motor will be stock.

    Will be rebuilding carbs again but wanted to dial in what springs to use from the kit and what pop-off setting should be (I understand that it will vary slightly from ski to ski).

    Group K recommends keeping stock jets, but I’m curious what others might have used?

    I want out of the hole “grunt” as I’m 46 and the high-speed falls “suck”!!! Looking to keep the ski reliable for many years as it is a community runner when people come over.

    Appreciate Some feedback.

  2. #2
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: 1998 750SXI Pro POP-off question

    Quote Originally Posted by Corndog69 View Post
    Will be rebuilding carbs again but wanted to dial in what springs to use from the kit and what pop-off setting should be
    (I understand that it will vary slightly from ski to ski).
    When you rebuild carbs, you would be better off to ignore alternate pop-off specs.

    Instead, purchase 2 oem Kawasaki springs, and use stock seat diameters. Properly
    set the lever height to level with casting. The try to achieve a 1 psi difference between
    each carb.

    Quote Originally Posted by Corndog69 View Post
    Rebuilding Ng stock block with new kit but did buy ADA head to get 180psi compression to stay with high octane fuel. Bought
    used Factory limited pipe and aftermarket k&n filters and new boyessen reeds. Other than those mods, motor will be stock.
    The most important thing to worry about here is the impeller and a peak rpm goal of
    7000 rpm in order to have a reliable set-up. Get a tachometer!

    The Boyesen reeds are a waste of money. In general they will increase the bottom
    end response, and loose peak HP. I have not dyno tested the 750 and dual stage
    reeds, but on the engines that have been tested, the reeds consistently lost peak HP.

    The Mikuni manual states that if you remove a restrictive flame arrestor and replace
    it with a free flowing flame arrestor, that you should lower the pop-off. I have only
    experienced this with old JS550's with the BN 44mm carb and the stock FA made from
    pumice.

    The manual came out in ~1992, and at that time all manufactures had free flowing
    flame arrestors, including SeaDoo. Kawasaki and Yamaha had the most free flowing
    flame arrestors, and do not require a pop-off change.

    The manual has a flaw IMO, lowering pop-off seems to fix everything.


    Bill M.

    Don't forget to purchase a decent exhaust manifold if your pipe has a 650 exh
    flange. Try to stay away from exh manifolds that have an increased flange diameter.

    Check the condition of the headpipes (3) water adjustment screws. It is very possible
    they will need to be replaced.

    If you keep the Boyesen reeds, your pilot screws may require a slightly leaner
    setting for best performance.

    Do not disassemble the carb rack, unless you remove the intake manifold and
    use it as an assembly jig. Replace all gaskets!
    Last edited by wmazz; 02-05-2018 at 08:27 PM.
    Horsepower == Speed, RPM != Speed



  3. #3
    Resident Guru 2strokesmoke's Avatar
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    Re: 1998 750SXI Pro POP-off question

    I had your same set up. With oem reeds and aftermarket ProK flame arrestor I used:

    75 pilots
    147.5 mains
    Dull silver spring

    Ran perfect. Lots of bottom end and topped out at 52mph with the stock 9/17 skat-trak. 7200 rpm with 80mm nozzle
    Last edited by 2strokesmoke; 02-05-2018 at 10:41 PM.

  4. #4
    PWCToday Newbie Corndog69's Avatar
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    Re: 1998 750SXI Pro POP-off question

    That is perfect!!! I had the nozzle bored as well and added stubby cone. Do you happen to know what your pop-off might have been?

    Thank you!

  5. #5
    Resident Guru 2strokesmoke's Avatar
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    Re: 1998 750SXI Pro POP-off question

    Sorry. I never measured it. It ran great so I was happy lol.

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