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Rare carbs

Discussion in 'XJ Technical Chat' started by wizard, May 14, 2012.

  1. wizard

    wizard Active Member

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    These carbs are fitted to a '85 xj 750, they have 4 spigots not seen on any other carbs, is anyone running these, be nice to get some feedback.[​IMG][​IMG]
     
  2. midnightmoose

    midnightmoose Member

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    Perhaps its a fuel overflow valve? Does each Carb have one? I'm sure someone else will know for sure
     
  3. RickCoMatic

    RickCoMatic Well-Known Member

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    A Blind Plug belongs there.
    That's a point where the Passage's are drilled.

    I'd guess it was an attempt to provide Auxiliary Air to the Pilot or Enrichment Circuit.

    If there is a Port drilled from inside the Diaphragm Bowl that meets that Opening at a Right Angle, ... It might be an Atmosphere Vent.
     
  4. Bushy

    Bushy Active Member

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  5. ol_750

    ol_750 Member

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    My 2 XJ750RL's have the hoses on the Carbies
    The 750RL supplement to the 900 manual show the hoses in the carby information but says nothing about them.
    I have the supplement as a PDF if you want it.
     
  6. jmilliken

    jmilliken Well-Known Member

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    i just picked up an 85 xj700 maxim.... and i have the same thing on those carbs. there's drain hoses off of all of them.... dunno what's up with that....
     
  7. wizard

    wizard Active Member

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    If you plug those you get an impossibly rich condition, the hoses must be exactly 10" long & they lean out the mixture as the revs increase.
     
  8. RickCoMatic

    RickCoMatic Well-Known Member

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    I rummaged thru all my Carb Bins and couldn't find a one that has a hose fitting there.

    I looked at a Hitachi sites.
    Couldn't find it listed.

    Checked the 750RL Site.
    No specific information.
    The 750RL Carbs View shows the Hose w/o a P/N.
     
  9. wizard

    wizard Active Member

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    They are HSC33s. very rare & I might add a PITA.
     
  10. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    I think "atmospheric vent" is a good possibility based on the behavior you're describing.
     
  11. wizard

    wizard Active Member

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    You're probably right, Fitz, but is there a 'special' way to sync the swines.
     
  12. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    You may need to block-off those vents when synching?
     
  13. wizard

    wizard Active Member

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    Reading up on atmospheric vents, they would appear to have the opposite effect, because the AVs force the float down & produce a richer mixture, whereas the more air these suck the leaner it becomes.
     
  14. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    Could it be that those are for the Calif. version that would have the canister behind the right side cover?

    Dave Fox
     
  15. xjlenordski

    xjlenordski Member

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    Hi Wiz,

    My 84 750RL has those same pipes (1 on each carb) with Hitachi carbs.
    I have just rebuilt the carbs with all parts from Len (isn't he great!) including throttle shaft seals & float needles & seats.
    I have done a bench sync & re-fitted them & it runs ok-ish.
    I am up to doing a running sync (but I have no YICS tool), so I'm interested to see what other info you get on this one.

    Cheers,

    Tim
     
  16. wizard

    wizard Active Member

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    +1 Len is simply the best, rock on XJ4EVER.
     
  17. RickCoMatic

    RickCoMatic Well-Known Member

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    Cut the Botttom Hem off a Cotton T-shirt.
    ::: Mostly Cotton :::
    Then, ... cut the Bottom around the waist making a continuous ribbon of T-shirt one-half inch wide.

    When you get a 20-foot ribbon of T-shirt, ... wind it into a Ball and soak it with Marvel Mystery Oil.
    Wring-out the excess MMO.

    Open the YICS Passage.
    With a Rod or Dowel, ... Unwind the T-shirt and STUFF it into the YICS Passage.
    Pack it tightly :::: (From BOTH Ends)

    Once the Passage is stuffed full ...
    Apply the End Caps and Go-about Vacuum Syncing.

    Before you begin ...
    BENCH Sync the Throttle Plates with an Ultra-thin Medium.

    ::: 3X5 Card Strips -- Business Card Strips -- Resume' Paper Strips -- 35mm Negative Strips :::
     
  18. jmilliken

    jmilliken Well-Known Member

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    So.... here's my question, can i swap these out on my 86? same hitachi 33's, but with the plug instead of the vent?
     
  19. RickCoMatic

    RickCoMatic Well-Known Member

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    Write=down all the Jet Sizes.

    If they'll bolt-up, ... give 'em a shot.
    Try to find-out what those upper Hose connections are actually for.

    You might get lucky and run like a champ.
    Or, maybe you'll need to tune and tinker.

    Good Luck.
     
  20. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    1986 versions of the HSC33's used on the XJ700 air-cooled engines do NOT have those brass vac ports..........only the 1985 versions have them.
     

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