750 ssxi carb tuning
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  1. #1
    PWCToday Newbie js550uscgman's Avatar
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    750 ssxi carb tuning

    Ok I bought the coffman pipe for my 94 ssxi 750 and its not running right, i heard that when you buy the pipe new it would come with the jetting and the way to set the cards up for it well I bought my pipe used and didnt get the sheet, Does anyone know how the carbs are supposed to be set onc you install the pipe on the ski. Please help the 4th is soon and tring to get it running good before then.

  2. #2
    PWCToday Newbie js550uscgman's Avatar
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    Re: 750 ssxi carb tuning

    bump

  3. #3
    PWCToday Newbie
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    Re: 750 ssxi carb tuning

    Any info yet? In the same boat as you..

  4. #4
    PWCToday Guru scottw090's Avatar
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    Re: 750 ssxi carb tuning

    you'll want to open the needles up and see if that does what you need. if you get passed like 2 turns out you will want to put a larger jet on the low circuit. While youre in the carbs go ahead and confirm your internal filter is free of debris.

  5. #5
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: 750 ssxi carb tuning

    I have used these carbs on a lot of 750 conversions. These should be the 40mm 3 jet type, with the jets 72 45 135. All three should be on the same side (later Keihins were different and I can't speak to their jetting.

    Ironically, for as much as I have used these carbs, I haven't tried this jetting on an actual ss xi or my xir. But the theory is the same. You need way more low and mid fuel, and a bit less up top. With aftermarket flame arrestors and a pipe, I have had very good results with 78 50 132. If you want to be a bit more conservative you can keep the 135 up top, and slowly turn in the high screw and see if rpm / speed continues to increase. I found that it's so much extra fuel down low, you need to reduce the main jet to compensate. Turning in the high screw with a 135 jet may not be enough.

    No needle and seat change is required with these jets. For these carbs at least, the bigger jet is the way to go about compensating for the fuel needs and not needle and seat change. That info comes from wmazz. The bigger mid jet helps compensate for an inherent lean spot these carbs had stock. After talking with wmazz, I believe the main issue with these carbs is that they were really optimized for fuel economy on the sit downs. As such when you add mods you really have to compensate on the jetting, more than you would on other carbs. I never noticed the mid range hesitation and lack of throttle response on my skis with these until I cured it, and had absolutely crisp throttle response bottom to top. As set up, they should be pretty much equal in throttle response to the 750-800 dual Mikunis on big pins, which I still find pretty surprising.

    We have run these settings on:
    3 or 4 550/750s including Hydro-Mike's old ski and Still Standing's old ski
    650sx/750 dual carb with a coffmans pipe
    750x2 with a blaster pipe
    Another few from the forum which aren't local but appear to have had good results

    Hope that helps.
    1985 JS550/800 "Pretty Red": Newmiller 800, Rhaas 750 pump conv. [56.3mph gps]
    2009 1100 SJ:
    Kawi 1100 build in progress
    2009 SJ MINT:
    KP steering adaptor, Worx 228 intake [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1995 SJ MINT:
    [TBD]



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