97 GTI carb settings?
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  1. #1
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    97 GTI carb settings?

    what are the correct carb settings to start with on a 97 GTI engine, The manual shows the low speed @ 1 3/4 and the high speed at 0. The seadoo reference guide shows the low speed at 1 and the high speed at 1 1/2, what is the best settings?

  2. #2
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: 97 GTI carb settings?

    It has been too long since I tuned a 97' GTI, but the idle drop test will get you
    close, especially if you decreased the pop-off.

    On many of the SeaDoo's the idle drop test settled in ~3/4 turn, but SeaDoo's
    have a really large return line jet orifice, and that allows the engine to idle
    with the larger than normal pilot screw settings (like 1-1/4 to 1-1/2).

    So, on a SeaDoo increasing the pilot screw adjustment an extra 1/4 to 1/2
    turn past idle drop test result should get you really close to a factory setting.

    It is more important to set the pilot and low speed circuits before the high
    speed because of the overlap. So after you are through with the pilot screw,
    set the hi speed to 1 turn, and if it is too rich lean it out.


    Bill M.

    Just out of curiosity, what was the problem that required a carb overhual?
    Last edited by wmazz; 10-22-2021 at 04:04 AM.
    Horsepower == Speed, RPM != Speed



  3. #3
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 97 GTI carb settings?

    97 is the oddball. Should be single carb with NO acc pump. If so, then 1 1/4 for low and 1 1/2 on the high. Then make any adjustments from there WITH F/A IN PLACE.
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
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    '99 Yama GP1200 65U 61.8 GPS
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    '96 Seadoo HX 717 53.13 GPS
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  4. #4
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    Re: 97 GTI carb settings?

    Here is the set up on this carb Main 175, Pilot 67.5, needle 1.5, pop off at 30psi, low speed 1 3/4 High speed 1 1/2. PSI both cylinders at 150psi. It starts ok but has a hesitation between 2,700 and 2,800, after that it will rev to 7K, it sounds like a lean type hesitation. I will adjust the pop off next- lower. I have tried all kinds of adj with the slow and high speed screws, no help

  5. #5
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    Re: 97 GTI carb settings?

    Pulled the carb off and set the pop off at 24psi. will test Sunday.

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    Re: 97 GTI carb settings?

    Has the carb been rebuilt? Aftermarket kits can have this effect.
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

  7. #7
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    Re: 97 GTI carb settings?

    I use Mikuni parts kits

  8. #8
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: 97 GTI carb settings?

    All too often people on this forum seem to think "pop-off" is
    some kind of silver bullet. Problems occur for a reason, something
    causes that problem and because someone !%@#** POS posted
    his opinion that pop-off should be between 24 to 18psi, everyone
    thinks the manufactures who sold the watercraft were incompetent.

    When the ski was new, or several yrs old and had no problems, was
    the pop-off too high back then too?

    Stop using bandaids, and just fix the problem.


    Quote Originally Posted by homebrewdoo View Post
    Here is the set up on this carb Main 175, Pilot 67.5, needle 1.5, pop off at 30psi, low speed 1 3/4 High speed 1 1/2. PSI both cylinders at 150psi. It starts ok but has a hesitation between 2,700 and 2,800, after that it will rev to 7K, it sounds like a lean type hesitation. I will adjust the pop off next- lower. I have tried all kinds of adj with the slow and high speed screws, no help
    Quote Originally Posted by homebrewdoo View Post
    Pulled the carb off and set the pop off at 24psi. will test Sunday.
    Stock pop-off was 38psi with an 80gr spring and a 1.5 seat. Most
    likely you installed a 65gr spring for 32psi, and either bent the tab
    upwards, or cut the spring to get 24psi.


    Your description of lean @2,700 and 2,800 falls on the low speed jet, and
    how it transitions to the main. The 720 has issues with it's intake manifold.
    If you fixed the problems, you would have a baseline to fix your hesitation,
    if it still exists (with the stock 80gr and 1.5).

    Increasing the low jet 2 to 3 sizes (~72, maybe a 75), and readjusting the
    pilot screw with the idle drop test will properly set the pilot screw to the
    new jet specs.

    Ever since the early 1980's motorcyles, atv's (that were not exempt), and
    watercraft were smog tested for emissions at an idle. So the manufactures
    developed jet specs around a lean low jet. Some times they also used brass
    caps to prevent the pilot circuit from being adjusted. Lean low speed circuits
    had the added benefit of decreasing the gallons/hour rating.

    The need for a lean low speed circuit is why they adopted accelerator pumps.


    Bill M.


    Quote Originally Posted by wmazz View Post
    It has been too long since I tuned a 97' GTI, but the idle drop test will get you
    close, especially if you decreased the pop-off.
    After you change the pop-off, any specs for the pilot(low) speed, and hi
    screw adjustments you have from the manufacture or elsewhere is just a
    guesstimate.

    I have worked on watercraft and motorcycles that had transition problems
    that were an acceptable trade-off for the manufacture trying to balance
    emission testing and performance. The manufacture didn't consider this
    as a defect.

    But they still paid for changes to the low speed jet or low speed by-pass
    holes as a courtesy for our time with a particular customer.
    Last edited by wmazz; 10-22-2021 at 07:34 PM.
    Horsepower == Speed, RPM != Speed



  9. #9
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: 97 GTI carb settings?

    Also, I would think anything under 30psi would be too low for a 717. They are shakers and will shake the needle right off the seat and dribble at idle making the engine untuneable. " All too often people on this forum seem to think "pop-off" is
    some kind of silver bullet."......I have to agree with this! I've had popoff from 35-65 psi on the exact same engine (well tuned), and could barely tell a difference.....and I do this for a living....adjust hundreds of carbs a season. If this were piped and ported, I'd say you were on the right path.....lower the popoff. BUT, on a stock engine the stock specs should work. Are you sure all the tiny holes just under the throttle blade were clear? A plugged one could cause a bog at the low to mid transition. Does the warmed up idle speed change with low speed screw adjustment?
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

  10. #10
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    Re: 97 GTI carb settings?

    Myself, you may have the answer with low speed screw, it had very little effect on idle, I will take a close look at the holes. thanks

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