90 587 GT jetting Q
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  1. #1
    Resident Guru DamageInc's Avatar
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    90 587 GT jetting Q

    Buddy of mine brought by a 1990 Seadoo GT 587 that's got a set of 38mm mikuni round body carbs. They're in pretty bad shape, so he picked up a set of sbn 38's.
    They reportedly came off a 90 GT 587 as well.
    I looked at the Seadoo carb source chart for this model, but it says 110 on the mains, and a ?mark for the pilot and n/s.

    Does anyone happen to know proper jetting and screw settings for this model?
    Bone stock ski.

    Thanks for any help.
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    Resident Guru DamageInc's Avatar
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    Re: 90 587 GT jetting Q

    As of now, it's got a 102.5 main and 62.5 low. Don't know the n/s/spring setup is o.
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    Re: 90 587 GT jetting Q

    Quote Originally Posted by DamageInc View Post
    so he picked up a set of sbn 38's. They reportedly came off a 90 GT 587 as well.
    90' used round body carbs, 91' used sbn carbs.

    The round body carbs have good low speed bypass holes for improved acceleration.

    They would be good dual 38's for a js650.


    http://seadoomanuals.net/manuals/1991-seadoo.php



    Bill M.

    Be careful, the 1991 rotary valve covers had problems with the RV clearances.

    I would flat sand the intake manifold, rv cover, replace the o-ring and inspect
    the oil pump seal by removing the plastic gear. The pump seals tend to fall out.
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    Last edited by wmazz; 05-26-2019 at 03:07 AM.
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    Resident Guru DamageInc's Avatar
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    Re: 90 587 GT jetting Q

    Thanks for the info, Bill.
    So are you saying that I can't, or shouldn't use the sbn set over the round body's? If so, why, and if not, is there jetting for the sbn's...?
    The round body's seem to have and exterior fuel pump, and what appears to be a smaller second one. The pulse line, which is about 24" long, T's, and a second pulse line is connected to the tiny pump, which then feeds the carbs.

    I was hoping to avoid that by using a set of sbn''s that have their own internal pump.
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    Re: 90 587 GT jetting Q

    So the link you provided shows the 91 gt carbs are 38mm, 107.5 mains 65 pilots.
    Will these carbs he bought work, and if so, will this jetting be a good starting point.
    Or should I put the round bodies back on?

    Thanks
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    PWCToday.com Is My Home Away From Home john zigler's Avatar
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    Re: 90 587 GT jetting Q

    Put the SBN's on. Early Seadoo's with the early style pipe and round body carbs would be different jetting than the later Westcoast Pipe, and SBN's.

    It will run with your set up, nut you may need to tune and or even re-jet
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    Re: 90 587 GT jetting Q

    Okay. I'll put the sbn''s on this '90 587 with what's in them.
    102.5m 62.5p. I'll start at 2 turns out on the lows, and 2 on the highs. And tune from there.

    Am I understanding recommendation's correctly?

    And Bill, when you mentioned the rv cover and is clearance issue, was that for the 91 model, or the 90 as well? This one is a 90.

    Thanks for the input guys.
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    Re: 90 587 GT jetting Q

    And if I need to jet up, I'll do so and retest.
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    PWCToday.com Is My Home Away From Home Grumpy Old Guy's Avatar
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    Re: 90 587 GT jetting Q

    Quote Originally Posted by john zigler View Post
    Put the SBN's on. Early Seadoo's with the early style pipe and round body carbs would be different jetting than the later Westcoast Pipe, and SBN's.

    It will run with your set up, nut you may need to tune and or even re-jet
    X 2 bolt on & go.

  10. #10
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    Re: 90 587 GT jetting Q

    Thanks Grumpy.
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