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  1. #1
    PWCToday Regular
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    Sxr carbs on 750 small pin..... Needs some jetting help

    So I have a sxr 800 I just picked up with a blown motor. Mostly due to financial restraints I put a 750 small pin in there. I have it all back together now and it runs like crap so I assume I need to rejet. The ski is bone stock 2007 and I think the numbers on the jets were 132.5 for high and 72.5 for low unless I read them wrong. With no choke it rumbles rough, with choke on it dies so pretty sure I'm rich....
    Anyone know what size jets I should get?
    Also after you put in new jets do you have to turn theadjusters to fine tune?
    Should I just turn the adjusters to tune it with the same jets?

    I've never rejetted a carb before so any help is much appreciated.

    Thanks

  2. #2
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    Re: Sxr carbs on 750 small pin..... Needs some jetting help

    OK so I am looking through my manuals and the sxi has the same carb (I think) but the jetting is 67.5 for low which makes sense because it is lower, but the high speed is 147.5 which is higher..... I am thinking since it's a 750 engine and the carbs are the same sbn 40-38 that I should go with the sxi jetting...It seems weird that the high speed is so much higher though, can someone confirm if I'm on the right track before I go and order new jets????

    MUCH APPRECIATED!!!!!!

  3. #3
    PWCToday Guru scottw090's Avatar
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    Re: Sxr carbs on 750 small pin..... Needs some jetting help

    Quote Originally Posted by Yabadabadoo View Post
    Should I just turn the adjusters to tune it with the same jets?

    Start with that. don't try to tune it without the pump in the water. strap it to the trailer and go to the ramp.

  4. #4
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: Sxr carbs on 750 small pin..... Needs some jetting help

    SXI's came with dual Keihin carbs, 1998 and newer Sxi-Pro and SXR's have dual Mikuni BN40-38 I-body carbs. You cannot compare the two carburetors as far as tuning specifications.

    For the Mikuni's with stock flame arrestor start tuning with the stock jetting. For free flowing a/m flame arrestor like Prok or similar start with:
    main = 152.5
    pilot = 80
    N/S = 1.5
    spring = 80 gram

    If you want to tune a carburetor correctly, read and understand pages 13 thru 17 http://www.mikuni.com/pdf/sbn_manual.pdf



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  5. #5
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    Re: Sxr carbs on 750 small pin..... Needs some jetting help

    Quote Originally Posted by mcn6 View Post
    SXI's came with dual Keihin carbs, 1998 and newer Sxi-Pro and SXR's have dual Mikuni BN40-38 I-body carbs. You cannot compare the two carburetors as far as tuning specifications.

    For the Mikuni's with stock flame arrestor start tuning with the stock jetting. For free flowing a/m flame arrestor like Prok or similar start with:
    main = 152.5
    pilot = 80
    N/S = 1.5
    spring = 80 gram

    If you want to tune a carburetor correctly, read and understand pages 13 thru 17 http://www.mikuni.com/pdf/sbn_manual.pdf
    I should have wrote sxi pro, that's the one I looked up. If the carbs for the sxi pro are the exact same as the sxr carbs and now I am using those carbs on a 750 engine, wouldn't that mean I should use the stock jetting as recommended for the sxi pro rather than the sxr? I don't understand why I would use the jetting for the 800 motor when I have a 750??
    And yes, I found that mikuni book and reading it now.

    Thanks a lot

  6. #6
    Resident Guru bored&stroked's Avatar
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    Re: Sxr carbs on 750 small pin..... Needs some jetting help

    I ran 75/147.5 on my small pin with 40i's and open k&N's. Wasn't perfect but never failed me either.
    '90 Superjet: ported 760, dual 44's, B pipe, ADA head 190psi, TDR waterbox, hooker 10-16, sponsons. Girlfriends ride
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  7. #7
    Top Dog bandit88's Avatar
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    Re: Sxr carbs on 750 small pin..... Needs some jetting help

    The porting of the 800 is much closer to a small pin than what the sxi is. I would guess you will end up with sxr porting with a size or two smaller on the pilot.
    -95 750SXI
    -86 440 with PJS800 conversion
    -90 TS650

  8. #8
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    Re: Sxr carbs on 750 small pin..... Needs some jetting help

    Ok now I f'd something up... Rrrrr.
    I took the carb apart and cleaned out the passages as one side was not flowing, now it won't start at all! I still have spark, and it looks like way too much gas!.. There is fuel flowing from the jet inside the smaller inside venturing when trying to start, isn't that the high speed jet? Should fuel be flowing through that at start up? If not what do I do/what should I do?... Ah man, I hate carbs!.... Thanks

  9. #9
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    Re: Sxr carbs on 750 small pin..... Needs some jetting help

    Quote Originally Posted by bandit88 View Post
    The porting of the 800 is much closer to a small pin than what the sxi is. I would guess you will end up with sxr porting with a size or two smaller on the pilot.
    OK thanks Bandit, so the porting effects what size jets to use?..... Carbs are above my pay grade... Lol
    The engine is full of fuel, I pulled the plugs, turned off the fuel selector, then turned over the engine and fuel was just spraying out so I assume my needles are leaking, unless it could be something else?
    Im pulling the carbs and I guess doinv a leaking down and pop off test (which I just sort of learned how to do) amd I'll see what happens there. I ordered some 70 and 67.5 low speed jets and I guess Ill try those out.
    Thanks for the input guys, much appreciated as I find carbs so Friggin frustrating!

  10. #10
    Top Dog bandit88's Avatar
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    Re: Sxr carbs on 750 small pin..... Needs some jetting help

    Yep, sounds like the needles are leaking. I would suggest changing the needles and seats if those carbs are unknown to you.

    There are lots of factors that determine the carburation and porting is a large one.
    -95 750SXI
    -86 440 with PJS800 conversion
    -90 TS650

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