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XJ900 Mukuni Carb Pics 2 - Cleaned - VERY PIC HEAVY - 58 Pic

Discussion in 'XJ Technical Chat' started by Alive, Mar 29, 2007.

  1. Alive

    Alive Active Member

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  2. Hired_Goon

    Hired_Goon Member

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    Re: XJ900 Mukuni Carb Pics 2 - Cleaned - VERY PIC HEAVY - 39

    Excellent pics Alive. Nice to see a shiney clean set of carbs.


    Some good measurements for interchangability would be measurements between each carb and throat size. I presume the 900 is 35mm.

    Good to see the differences even between different Mikuni models. Yours are very similar to my XS1100 BS34 Mikunis with some subtle differences. Mainly in different air mixture screws but a few others as well.

    Also very similar to my XJ550 28mm Mikunis but again still has some minor differences.

    Keepup the good pics. A great learning tool for all.
     
  3. FinnogAngela

    FinnogAngela Member

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    Re: XJ900 Mukuni Carb Pics 2 - Cleaned - VERY PIC HEAVY - 39 Pic

    Damn, that´s good work!

    2 questions:

    - are the "caps" above the mixture screws a replacement solution for the originals?

    - arent you in trouble having seperated the carbs from the rack?

    Again, invaluable pics for anyone cleaning those carbs.
     
  4. PghXJ

    PghXJ Member

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    Re: XJ900 Mukuni Carb Pics 2 - Cleaned - VERY PIC HEAVY - 39 Pic

    very nice pics. Where did you get all those new parts? new nozzles and everything...wow. All I see are carb rebuild kits that have a new float valve and float bowl gasket and a couple o-rings.
     
  5. Alive

    Alive Active Member

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    Re: XJ900 Mukuni Carb Pics 2 - Cleaned - VERY PIC HEAVY - 39 Pic

    I don't know if they are replacements or not... They were on them when I bought the bike.

    I didn't want to split them, but it sure does make it a whole lot easier to clean. With these ones there isn't really an issue because once you have the bar with the idle screw and the top bar off, the only things holding them together are the fuel & breather connectors and the small springs on the bottom of the balance screws so it will be pretty easy to get them back together as a rack without even putting them out of balance... Hopefully :lol:
     
    dgroot likes this.
  6. Alive

    Alive Active Member

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    Re: XJ900 Mukuni Carb Pics 2 - Cleaned - VERY PIC HEAVY - 39 Pic

    The only new parts are the Float Valves and slightly bigger Main Jets the rest was just cleaned in degreaser then lightly scrubbed with a toothbrush sized wire brush :)
     
  7. RickCoMatic

    RickCoMatic Well-Known Member

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    Re: XJ900 Mukuni Carb Pics 2 - Cleaned - VERY PIC HEAVY - 39 Pic

    Wicked-GOOD Photography.

    Those Caps over the Screws are a nice touch. They aren't on my 900 and I'd love to have a handful.

    Do you have a special lens for the Close-up work?
     
  8. Alive

    Alive Active Member

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    Re: XJ900 Mukuni Carb Pics 2 - Cleaned - VERY PIC HEAVY - 39 Pic

    I'd love to have a few spares too :)

    I went on a trip to Fiji for a week last year and needed a decent camera and ended up buying one of these:

    JVC Camcorder

    Great camera as you can tell :)
     
  9. Alive

    Alive Active Member

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    Re: XJ900 Mukuni Carb Pics 2 - Cleaned - VERY PIC HEAVY - 58

    Just uploaded another 19 pictures 8)
     
  10. Polock

    Polock Well-Known Member

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    Re: XJ900 Mukuni Carb Pics 2 - Cleaned - VERY PIC HEAVY - 58

    after seeing those pictures i think i'll just throw mine away
     
  11. Alive

    Alive Active Member

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    Re: XJ900 Mukuni Carb Pics 2 - Cleaned - VERY PIC HEAVY - 58

    Don't forget that these carbs are off a bike thats only done 8k miles :)
     
  12. louis

    louis New Member

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    On my 81 xj750 seca i also have mukuni carbs The little rubber grommets that you put on your mixture screws are inside my carbs they are on the small jet next to my main jet could that be that i have got starting problems on my bike. I stripped and cleaned my carbs and put the grommets back where they came out. I have starting problems since i bought the bike, and my inrichmint circuits are clean I checked it 4 times already.Can you please tell me if it is rite or wrong.
     
  13. wingnut325

    wingnut325 Member

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    There are 2 types of Mikuni BS34s out there. The early models have the exposed idle mixture screws and there is a hole drilled between the main jet and the pilot jet. If you have that setup than you need the cap over the pilot jet. These early units usually have a larger main jet as the pilot jet fuel supply flows thru it. The later models have the encased or recessed idle mixture screw as shown in the pictures above. The later units have smaller jets and NO hole drilled from the main jet galley to the pilot jet. These should not have the plugs installed in the pilot jet hole as the pilot jet pulls its fuel supply directly from the fuel bowl. The later model also has a smaller main jet. I could not see from the pictures above if those had the hole or not. The little black caps that come in some kits are for the pilot jet galley on the early carbs. They jest happen to fit the idle mixture screw hole very nicely. There was some mixing and matching done by Yamaha on the 1100s in 80 but most of the 81 and later carbs were the later style that did not require the pilot jet caps in the fuel bowl.
     
  14. louis

    louis New Member

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    Thanks for the help i will try running the bike without them and see what happens.
     
  15. RickCoMatic

    RickCoMatic Well-Known Member

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    According to YAMAHA ... the 1981 750 Seca was equipped with Hitachi Barbs ... NOT Mikuni.
    Look at the Top Cover of the Carb.
    If there is a Slanted-type Ramp stamped into the Cover ... they are Hitachi's

    If the Carb Top Cover has NO Ramp, is Completely Round ... they are Mikuni

    Hitachi Carbs have Button Pilot FUEL Jets.
    Mikuni Carbs have Bullet Pilot FUEL Jets.
     
  16. littlegiant

    littlegiant Member

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    hi alive,
    Thanks for pictures..really helpful and i just went thur the carb cleaning on my Maxim X Mikuni carbs(XJ750) pretty much same and found that carb 4 had buggered pilot screw hence could not clean or adjust. Am going to put them on bike tommorw n see how it performs.
     
  17. Alive

    Alive Active Member

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    No prob... I hope they continue to help out others trying to clean theirs.

    Hopefully yours work well :)
     
  18. RickCoMatic

    RickCoMatic Well-Known Member

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    Your photography is exceptionally good.
    You Carbs are exceptionally well cleaned.

    I have sent to Australia a replacement for the Enrichment Valve.

    Scrub and Polish the Bores.

    (You can repair a broken-off Enrichment Valve Top by taking a Brass Screw and holding-it ... surrounded by 400 Paper while spinning it with a Screwdriver Bit to "Machine-shine away the threads"
    Drill the Valve Body.
    Put the Brass Screw in and solder it.
    Reheat set the depth and let cool.
     

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