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Carb Jet sizes

Discussion in 'XJ Technical Chat' started by Plug, Sep 22, 2019.

  1. Plug

    Plug Active Member

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    Hi all! I recently added another XJ to the stable. A 1983 750 Maxim. As I started tearing down the carbs, the first thing I have found is that the pilot fuel jets are 43 instead of 40, and the main fuel jets are 122 instead of 120. The jets do not look like they have ever been removed, not a scratch or a mark on them. The pilot air jets are 225 and main air jets are 80 like specified. Is it possible they came from the factory with these jets installed?
     
  2. Polock

    Polock Well-Known Member

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    probably not, but more important is how the plugs look
     
  3. Plug

    Plug Active Member

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    They actually look pretty good, but I do not think it has run much in several years, so I am not sure how good of an indicator that is. Am just kicking around if I need to order jets before I proceed, or if I will be able to get a good tune out of it with these jets. I only had 3 valves out of spec and they were not by much so it appears the maintenance has been kept up on as it has 33,000 miles on it.
     
  4. XJ550H

    XJ550H Well-Known Member Premium Member

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    http://xjbikes.wikidot.com/carb-specs

    not uncommon to up pilot jet.

    what do the jets look like ? flat where the hole runs through them or a cone shape to the hole.

    could be someone put an ebay cheap set to rebuild carbs they come with those sizes but jets are flat where hole goes through them.

    you should be able to tune them with those jets but will get less mpg

    maybe the PO was trying to get more out of the motor than the smaller jets would give him.
     
  5. Plug

    Plug Active Member

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    20190922_185920.jpg


    I went ahead and just ordered the 120s and 40s from Chacal.
     
  6. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    Those are Hitachi jets, but they sure aren't 36 years old (unless you cleaned them already).
     
  7. Plug

    Plug Active Member

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    No Sir...as I found them. Got correct ones on the way
     
  8. RonWagner

    RonWagner Member

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    I usually run one size over in the early 80s bikes. They were set up lean from the factory. The larger keys may hurt mpg but will start easier, run cooler, and you won't need to run the choke as long warming up. You will get a little more power too.
     

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