SBT Jetski Engines, Parts & Accessories

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  1. #1
    Joined
    Jul 2005
    From
    Austin, TX
    Posts
    1

    Default JS550 Carb problems, replace it?

    Hello,

    I just bought a couple of skis. The mid 80's 550 runs well until it wants to foul the plug on one cylinder. Rather than play the tuning/rebuild/tune again game with this thing I would rather just replace the carb, tune it, and be good to go.

    I imagine the carb has been rebuilt a handfull of times given its age, and each person probably stuck wires in all the passages, etc.

    So which carb is a direct replacement for the stocker? As a motorcycle performance shop I have access to new Mikuni super BN carbs in the 34, 36, 44, 46mm range. The watercraft is all stock except for a pipe.

    I want to get this thing reliable so we can ride it without messing with it. Compression is 145psi per cylinder.

    Thanks for your help guys,

    Jon

  2. #2
    Joined
    Jul 2005
    From
    central NC
    Posts
    14

    Default Re: JS550 Carb problems, replace it?

    I'd put a FP chip in it, then sync the TB's and, whoops, sorry, wrong forum :D

    Hey Jon! imagine running into a "familiar face" over here -

    I've got an '88 JS550 that I've modded pretty well, and I just found this site and was just looking around...

    The earlier model 550's had the BN38, but later models had the BN44, which has proven to be the overall best carb for the 550. Check yours out - if yours has a BN44 (40 mm venturi) and the body is in good condition - hopefully the PO didn't damage it - these things are simple to work on. The Mikuni rebuild kit (~$40) is no sweat to do. You will need to be fairly familiar with the carb's workings to properly set it up anyway - it would be good to verify the pop-off valve pressure is correct. If you want to try your hand at pumper carb tuning, just let me know - I kept all my vintage magazines that have the tuning tips and procedures.

    If you've got a smaller carb or it's trashed, there may be some guys on here with more knowledge about swapping out for a new gen carb. You oughta love it - the old JS hull with a good running 550 is a killer combo, particularly in the surf! - good luck!

    Tony ("prillernut")

    - I just found this thread -
    http://www.sbtontheweb.com/forum/showthread.php?t=10846
    Last edited by prillernut; 07-13-2005 at 05:14 PM.

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