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Different Country Different Jets

Discussion in 'XJ Technical Chat' started by Tomq, May 30, 2017.

  1. Tomq

    Tomq Member

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    Hey guys,

    This is purely just out of interest and I've googled it and can't find a simple answer. I'm super new to bike mechanics and I've just started my first restoration of a 81 XJ750RH.

    Im half way through rebuilding the carbs and my question is why different countries have different jetting set ups? Whats the pros and cons of re jetting and why would you do it? I don't even really know exactly what the jets do so any links or links to discussions on here would be great.

    Cheers in advance!
     
    Tomq, May 30, 2017
    #1
  2. Jetfixer

    Jetfixer Well-Known Member

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    Emission is one item , another is altitude. Now when dealing with a bike that is 30 years old and is long out of waranty safe to say exhaust changes if owner has fitted my dreaded PODS then anything is game. When new jetting was lean going up one or two sizes larger usually helped this. In my seca 750 I'm running a 124 main and 41 pilot with the stock airbox but I have a MAC 4 into 2 exhaust. Runs great....
     
    Jetfixer, May 30, 2017
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  3. XJ550H

    XJ550H Well-Known Member Premium Member

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    Read This First


    EPA regulations differ between countries. in the 80's U.S. has one set of rules Canada has another set of rules, and the rest of the world differs from U.S.
    as far as the jetting you can pick what ever setup you want to jet to there is a list at this link http://xjbikes.wikidot.com/carb-specs
    what jets do and when



    THE SECRET LIFE OF CARBURETORS

    TALKIN' TECH: Various thoughts on various issues
    from above link
    The pilot fuel circuit is active from idle up to about 2500-3500 rpms, and at about 3000 rpms the main fuel circuit starts becoming involved, and by 4000+ rpms the main fuel circuit is responsible for about 80%+ of the engine's fuel supply conditions.

    The Information Overload Hour
    .
     
    Last edited: May 30, 2017
    XJ550H, May 30, 2017
    #3

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