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  1. #1

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    Initial carb tuning... and low speed adjusters

    I have read the mikuni manual. Need some clarification.

    Manual states that low speed adj. is only used to obtain smooth idle.

    I'm sure I don't start with closed LS adjusters, so where should I start? 1/2, 5/8, 1, 1 1/2 turns out????

    I know I've tried in the past to turn in the LS adjusters for tuning and went lean and died off idle, and to the other extreme turned out the LS adj. and bogged from being rich off idle....both with smooth idles.

    See what I am getting at here?


  2. #2
    cheatin' piston popper addicted's Avatar
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    start with both at 1.5 out. Work on the LS first, then the HS. Not seadoo specific, but should get you going. Always, always start rich and lean it out

  3. #3

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    So the mikuni manual that states the low speed adujusters have absolutely no effect except to maintain a smooth idle is kind of like those fire works you buy, you know the ones that say light fuse and get away!!

  4. #4
    David 1 FAST VE's Avatar
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    Low speeds carry you from Idle until your N&S open.
    They are doing something you just have to know how to listen.

    It is not a good idea to use low speed screws to compensate for a small low speed jet either so both must be right.

  5. #5

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    So, aside from listening, which I'm not sure i Have that skill yet, if the low speeds are 2 out and still running lean off idle, that would be a good indication the LS jet is too small?

    Sounds like what you guys are saying is get the low speeds dialed ,and then set the idle. then proceed with the higher throttle testing.

    I've read that darn manual so many times. First time out with out any "for sure" jetting specs.

    Thanks for all the help guys.

  6. #6
    GTXX's Avatar
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    get the LS adjusted in the 1 1/4 to 1 3/4-2 turns open range so that it runs good transitioning from idle, then set idle speed. too low of a pop-off will give you problems too, what is it? what jetting do you have?

  7. #7
    GTXX's Avatar
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    2.0 NS, stock spring, stock high speed jets, 10 numbers larger than stock on the lows usually works good.

  8. #8
    MILLER PHASE 3 1050's Avatar
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    what motor are we trying to blow up here anyways ?

  9. #9
    Faster Than a Snail on a Log mongorunner's Avatar
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    Quote Originally Posted by MILLER PHASE 3 1050 View Post
    what motor are we trying to blow up here anyways ?

    i was just passing though but couldn't help myself


  10. #10

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    It is a 96 gsx GK sleeper, Rossier Pipe, NOVI modified 40mm I series carbs, now 42 MM NOVIS.

    Jetting is 170 highs, 80 lows, 80 gram springs for a pop off of 15psi. 2.0 needle and seat.

    With a 77.5 LS jet the pop off was 18psi.

    This is 27.5 more total jetting than the GK sleeper 40mm true bore carb setup. Most additional jetting comes on the high end.

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