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  1. #1
    de922's Avatar
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    Some carb tuning advice needed

    I`m having problems with the 44`s on my Ultra 150.
    Whatever jet sizes,mixture settings i have tried so far i can`t get past 6400 rpm at wot

    idle speed is also acting strange. in water idle is 1200 rpm while out of water idle is over 3000 without touching the throttle


    carb settings are

    2.0 N/S
    95g spring
    100 highs 1.5 turns out
    112.5 lows 1.5 turns out

    any suggestions from the resident tuning gurus would be appreciated


  2. #2
    jonny5's Avatar
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    What type of carbs and how old since rebuild ...

  3. #3
    de922's Avatar
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    Click image for larger version. 

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ID:	315805Mikuni super bn`s purchased about 18 months ago .never been rebuilt

  4. #4
    jonny5's Avatar
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    Interesting is that the stock manifold ..? Haven't seen that yet but should be good for throttle response how does it match up with the carbs is there any lip..??

    As far as jetting I don't think your far off although I would switch the hi and low numbers but the n/s is good with spring.

    Carbs look clean from pic...?

    How is all the low speed and mid range ..? Not to abnormal for about 1200 in water and maybe a little higher out up to 3000 mm maybe not seadoo yes but not kawi with AFM carbs.

    Here is where you have to start from the top...

    Spark plugs good....
    Compression good
    Fuel good
    It ran fine before other carbs ..???
    Carbs are sinked ...

    As long as you know everything ran or worked before the carbs went on then you at least know the carbs are the problem.

    Then it would be making sure each carb is working correctly so do they need rebuild or no...?
    Is that manifold a problem and reeds are good and so on ....
    Need to make sure everything is good so we are pretty sure we can focus only on carbs and intake stuff

    K

  5. #5
    de922's Avatar
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    intake manifolds are from Group K
    by "switch hi and low numbers" do you mean reverse them? i have 110 highs and 105 lows
    spark plugs are NGK BR9EIX iridium 2-3 years old still look ok
    don`t know compression. 25 thou taken off heads, top end rebuild 2008
    only use 95 RON premium unleaded
    oem carbs ran fine. from memory reeds looked good not chipped or cracked

  6. #6
    jonny5's Avatar
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    First things first
    Change plugs even if they look good it's a cheap diagnostic and I have never ran a set longer then about 3 months but I was also racing but even a rec boat at least once a year.
    Really need a compression check you may have a cylinder down 20-30 psi or maybe a couple or who knows but need to know so we know motor is good.

    Make sure the plugs you buy are the ones it calls for...?

    I assume this is a ultra 150....2003
    I like the groupk manifolds I think they had the slimmest design which I think had the best throttle response.

    So compression check and new plugs

    And yes 110 highs and 100 lows or 95's or 105
    But yea the high number for your main jet.
    There are sometimes though when they flip the other way which I see more common on seadoo

  7. #7
    SplishSplash's Avatar
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    Same prop?

  8. #8
    de922's Avatar
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    new plugs are on the shopping list
    had a feeling you would mention the compression test again. hopefully borrowing a gauge tomorrow from a friend

    SplishSplash 16/20 solas

  9. #9
    de922's Avatar
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    ok jonny, i finally got the compression test done

    cyl 1 - 130 psi
    cyl 2 - 120 psi
    cyl 3 - 130 psi

  10. #10
    captainoverspray's Avatar
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    what happens when you turn your high speed in? You should pick up some of the RPM it is not over jetted in the main. Here is what I ran when I had 44's.

    115p
    110m
    2.0 n/s
    115g spring
    1/4 turn h/s
    3/4 turn l/s

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