1989 650 sx carb help
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  1. #1
    PWCToday Newbie
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    1989 650 sx carb help

    Hey everyone,

    So i'm conflicted after doing a bit of reading. I picked up a 89' 650 sx and want to get rid of the 28mm stock carbs. I've done a lot of reading on the whole 44sbn mikuni carbs or the alternative 40-42 Keihin 750 sx carbs with a later model intake and bore out the throat. So my question revolves around how much of a difference really is there in performance. I do like mikuni more than keihin, but there's a noticeable margin in price. Also, can you keep the stock exhaust with a 44? I've heard the stock exhaust does okay with the 40-42 Keihin's. Its something I don't want to turn into a money pit (as easy as it seems it can turn into). Lastly, I've heard the possible upgrades to adding a primer kit, not sure if thats only possible with one vs the other. I'm seeing full carb, manifold, and spark arrestor kits going for 300+ on ebay and that doesn't seem quite worth it.

  2. #2
    Top Dog Boz Mon's Avatar
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    1989 650 sx carb help

    If I had to do it all over again I would throw that keihin in the garbage and go sbn all the way. Cheaper rebuild kits, cheaper jets, easier to tune. IMO the sbn is waaaaaayyyy better than the keihin.


    I donít run primers in either of my skis and I donít even have the chokes hooked up. I use the choke for the first cold start of the day and thatís it. A healthy motor and a good dialed in carb do wonders for starting.

    Sent from my iPhone using Tapatalk
    Last edited by Boz Mon; 08-10-2018 at 01:05 AM.
    1994 FX1
    1985 JS550/650 conversion
    2015 Fiat 500 Abarth

  3. #3
    PWCToday.com Is My Home Away From Home freekstyle's Avatar
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    Re: 1989 650 sx carb help

    You answered your own question. You want more performance but for free. No such thing. Just ride it stock and have fun. Once you start modding a ski its hard to stop.
    Last edited by freekstyle; 08-10-2018 at 02:37 AM.

  4. #4
    I dream skis sportsfreak29's Avatar
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    Re: 1989 650 sx carb help

    Fork out the cash for a Factory Pipe, 44sbn with manifold, a Skat 9/17 and send your head to Newmiller Machine.

    This will turn your no go cruiser into an arm jerking monster.

    A Prowatercraft ride plate, and a set front and side sponsons will give you the handling performance to tame the beast.

    Lots of people bag on the 650sx, but with these mods, it will be a formidable machine.

    An aluminum MMF pole is a great addition after you finish getting the above mods done. It will help you get more weight forward and make it easier to keep the pump hooked up.
    If you're not crashing, then you're not trying!!!

    Ski situation in limbo!

    Special thanks to Chris Newmiller, and Mitchell at M&M Marine!

  5. #5
    I dream skis sportsfreak29's Avatar
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    Re: 1989 650 sx carb help

    I'm currently rebuilding a 650sx with the above mods. I had one years ago and loved it, but sold the hull when I had the opportunity to purchase a js550/650 pump swap hull built by another member on here, and have missed it ever since.

    The 650 motor is significantly detuned with the stock carb, compression and exhaust. The performance gains are SIGNIFICANT with the mods I listed above.

    The js550/650 is a monster high speed carver, but I miss the long high speed power slides that are possible on a 650sx which is more forgiving and a blast to throw around!
    Last edited by sportsfreak29; 08-10-2018 at 12:06 PM.
    If you're not crashing, then you're not trying!!!

    Ski situation in limbo!

    Special thanks to Chris Newmiller, and Mitchell at M&M Marine!

  6. #6
    PWCToday Newbie
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    Re: 1989 650 sx carb help

    where do I get a hold of newmiller machine. I also hear they do a good job with the flywheel. whats their prices on the heads? I can't find anyone selling 9/17 or 15.5 impellers.

  7. #7
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    Re: 1989 650 sx carb help

    freekstyle, you couldn't have been more right. It's a trap!

  8. #8
    Attention ***** PWCToday.com Is My Home Away From Home JonnyX2's Avatar
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    Re: 1989 650 sx carb help

    Quote Originally Posted by 207 View Post
    where do I get a hold of newmiller machine. I also hear they do a good job with the flywheel. whats their prices on the heads? I can't find anyone selling 9/17 or 15.5 impellers.
    Newmiller Machine is mcn6 here on the board. You can get a 9/17 directly from Skat Trak, or a reputable Hot Products dealer like John Zigler at WatCon. Use an 8/16 for a stock motor/pipe. Do not waste your time with a Keihin carb, there are many parts on those carbs you can not get anymore. Mikuni all the way.
    Last edited by JonnyX2; 08-19-2018 at 08:27 PM.
    Quote Originally Posted by Firebird A/C&Heating View Post
    OMG.....Rules for 550 vintage ski class...550 ski riders do not conform to any kind of rules. That is why you are riding a 550 ski in the first place. Rules suck....
    PS...the rule book will be in my 550 pump
    Quote Originally Posted by WB1994
    Listen , stop your cryin' , its only an X2.

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