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Idle Mixture Screw Cap

Discussion in 'XJ Technical Chat' started by Fishmaster, Nov 29, 2008.

  1. Fishmaster

    Fishmaster Member

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    Why the Toshiba carbs idle mixture screws comes capped?
    Did the engineers think that the carbs will never need to be rebalanced?
    How do you guys usually remove them?
    Are they located right next to the choke plunger, right?
     
    Fishmaster, Nov 29, 2008
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  2. stereomind

    stereomind Active Member

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    You mean Hitachi?... These bikes were set a tad on the lean side at the factory, lean enough to pass EPA regulations... then they capped them off so owners didn't "tamper" with the mixture settings therefore making the bike out of compliance with EPA.

    My favorite way of removing them is to drill a small hole (1/16" or 3/32" bit) through the cap, being careful not to plunge the bit and damage the idle screw, and use a sheetrock screw to pull the plug out... and you're right, they're next to the plungers.
     
    stereomind, Nov 29, 2008
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  3. Fishmaster

    Fishmaster Member

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    sorry I "mixed" the japanese makers
     
    Fishmaster, Nov 29, 2008
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  4. Fishmaster

    Fishmaster Member

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    stereomind,
    how thick is the cap?
     
    Fishmaster, Nov 29, 2008
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  5. MiCarl

    MiCarl Active Member

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    They're quite thick. They're not little sheet metal hats, but a brass disc. I've never measured one but I'd say 2-3mm thick.

    The key is to use a small, sharp bit at high speed so you're not using much pressure. You'll feel it punch through. If you're leaning into a big, dull bit it'll bugger the head of the mixture screw when it breaks through.
     
    MiCarl, Nov 30, 2008
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  6. Fishmaster

    Fishmaster Member

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    So the screw head is not touching the cap piece, right?
    In my carbs they look like aluminum.
    Tthank you guys, I will try with my Dremmel. I hope they come out easy with out damaging the screws.
     
    Fishmaster, Nov 30, 2008
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  7. wizard

    wizard Active Member

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    Hi fishmaster, I spent an hour yesterday trying to find your carbs, I also spent some time trying to find an '86 XJ700N, I did find an '85.
     
    wizard, Nov 30, 2008
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  8. Fishmaster

    Fishmaster Member

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    Wizard, the owners manual shows XJ700N-XJ700NC and the manual edition is from 1984. Maybe you're right and is a 1985. My brother in law purchased the bike in 1986. I don't know how to upload pictures to show you the carbs
     
    Fishmaster, Nov 30, 2008
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  9. Hack

    Hack Member

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    So, once the "caps" have been taken out to do the adjustments with the colortune, does anyone ever cover the opening afterwards to keep out dirt, etc.? I understand that they were initially installed by Yamaha to prevent tampering, but they also kept out crud. Maybe not an issue?
     
    Hack, Feb 20, 2009
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  10. wizard

    wizard Active Member

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    They don't need to be covered, in fact it's PITA if you want to have a fiddle, I mean tune. :lol:
     
    wizard, Feb 20, 2009
    #10

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