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rubber caps

Discussion in 'XJ Technical Chat' started by wolfmajor, May 13, 2013.

  1. wolfmajor

    wolfmajor New Member

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    Hi,

    I found a missing rubber cap on the carbs of my '85 Maxim XJ750 (airhead) and I'm not sure of what it is. I've had nothing but problems getting and keeping this bike running well and now I wonder if this could be the problem. Can someone name this part for me, please?

    Thanks!
    Cheryl
     

    Attached Files:

  2. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Those are vacuum ports, so they would be called "vacuum port caps." There should be (3) of them, and a hose running to your petcock (if it's vac operated) on the 4th, usually the #3 position.

    If you don't have the original, vac-op petcock, then all (4) should be capped. Those ports are only used for vacuum sync (and one to operate the petcock.)
     
  3. hogfiddles

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

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    it's been on the second port on almost all my bikes, but it really doesn't natter as long as its on one of them for the vacuum source.

    dave
     
  4. bensalf

    bensalf Well-Known Member

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    if you ca'nt get the rubber caps, nos. 1&4 , and 2&3 can be linked with suitable lengths of tube,
    my xj600 has these tubes fitted as standard with a "t" piece in the 1&4 pipe for the petcock vacuum.
    stu
     
  5. joeperezis

    joeperezis Member

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    You can also make them out of short lengths of black fuel hose with a "round head" brass machine screw (24 threads per inch) screwed into the short length of hose to block off one end. You can then secure the DIY vacuum port caps to the vacuum port with spring clamps sized to the fuel hose.
     
  6. maverickbr77

    maverickbr77 Member

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    don't know why you'd DIY/alter them (except as a temp quick fix) most auto places have a rack full of them for a couple of bucks a pack.
     
  7. wolfmajor

    wolfmajor New Member

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    Wow...thanks for the quick replies everyone. I was out for a few hours and came home to a list of responses. I had to remove the gas tank from the bike after realizing the petcock was leaking (ugh). This was a rebuilt petcock, so I'm a little bummed to have to go through this again.

    Thanks again to everyone for the great info. This is such a great group. :)

    '85 Maxim XJ700N
    Manchester, NH
    ** In need of a petcock rebuild **
     
  8. joeperezis

    joeperezis Member

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    Yeah, I tried three different auto parts stores locally and the ones that were "close" in size would not stay on.

    I was between parts order with XJ4Ever and this short term fix seems to be turning into a longer term fix. It also gives it a nice finished look with the round head brass showing at the top of each cap.
     
  9. Captainkirk

    Captainkirk Member

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    Just bought a set of new ones from Chacal, a couple bucks each. Old ones were hard as a rock. Just do it!
     
  10. bensalf

    bensalf Well-Known Member

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    --------------------------------------------------------------------------------------
    most auto places have a rack full of them for a couple of bucks a pack.
    ---------------------------------------------------------------------------------------
    really? never seen ,or heard of anything like them over here,--
    what would they be used for, generally?
    stu
     
  11. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Plugging/capping vacuum lines? They're generally sold with the hose fittings, caps, t-fittings, etc.
     
  12. KrS14

    KrS14 Active Member

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    Secondary YICS lol I wouldn't trust tying two of them together, there's too much that cause issues with tuning.
     

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