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re-jetting my carburetors

Discussion in 'XJ Technical Chat' started by jdoggsc, Jul 2, 2012.

  1. jdoggsc

    jdoggsc Member

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    Hey all, I just moved from 1387 meters (4000+ ft) elevation (where I was when i bought my xj) to 275 meters (~900ft) and I need to retune my bike because it's running super lean.

    I was told by a friend who is familiar with carburetors but unfamiliar with hitachis that I have a size 40 pilot jet and a size 110 main jet. he didn't really know what sizes those were, so he couldn't tell me what sizes to go to, but he said that I should go up about 3 sizes to adjust for the new elevation change (~3000ft)

    doing a quick calculation, I determined that the air is 14.4% more dense here, and he said that I would need to select a jet that was ~14.4% larger in area. Problem is, i don't know what the inner diameter is for a 110 jet, and i don't know what increments the sizes increase by.

    Anyone have any experience in this?

    Also, do I need to increase my pilot jet from 40 to 41?
     
    jdoggsc, Jul 2, 2012
    #1
  2. Metal_Bob

    Metal_Bob Active Member

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    Have you tried to simply adjusting the 4 mixture screws?
     
    Metal_Bob, Jul 2, 2012
    #2
  3. Ground-Hugger

    Ground-Hugger Member

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    That sounds to EASY we need a more in depth solution!!
     
    Ground-Hugger, Jul 3, 2012
    #3
  4. Metal_Bob

    Metal_Bob Active Member

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    Strip the bike. Reassemble wrong with parts left over. Take apart working carbs. Drop them and break float towers. Buy new carbs and clean them half arsed and spend all year asking for help in posts.

    That hard enough? :p

    Or adjust the 4 mixture screws IF NECESSARY. :)
     
    Metal_Bob, Jul 3, 2012
    #4
  5. mook1al

    mook1al Member

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    Metal_Bob has the best first angle of attack. The jets you have are stock and correct for your current alt. Try adjusting the idle mixture screws, starting at 2.5 turns out.
     
    mook1al, Jul 3, 2012
    #5

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