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Optimal Vac Readings

Discussion in 'XJ DIY How-To Instructions' started by Redman276, Apr 26, 2008.

  1. Redman276

    Redman276 New Member

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    Just out of curiosity can someone post the optimal Vac readings in general . just for a quick test with out any buffering , my xj700 read 17 mm/m on carb 1 and only 6 mm/m on 4 i known for years shes been out of sync so its riding season and i want to tune it up and get the idle under 3800 rpm as well .


    Red


    oh and mm/m is milimeters of meurcury , as i read the dial gage onthe el cheapo vac hand pump ( the only good thing that came from the wifes jeep - a diagnostic tool )
     
    Redman276, Apr 26, 2008
    #1
  2. Polock

    Polock Well-Known Member

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    as many times as i've done it, i can't say
    it's more important that they all be the same than what they actually are
    if i was going to win a million bucks i'd say 6 ?
     
    Polock, Apr 26, 2008
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  3. Hillsy

    Hillsy Member

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    What he said ^^^

    It doesn't matter what the reading, as long as they're the same.
     
    Hillsy, Apr 27, 2008
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  4. Redman276

    Redman276 New Member

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    ok , i wasnt sure , cause like i said , this was jsut a quick reading once i actually got the boots togo back on the "in side of the carbs , its been 3 yrs or so since i even messed with it and now i have time to work on it .

    it idles at 3800 rpm and just can barely make 50 mph before breaking up and cutting out , so it needs work .

    Thanks

    Red

    Canton, PA
     
    Redman276, Apr 28, 2008
    #4
  5. Redman276

    Redman276 New Member

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    ok so yesterdays chore was the sync.

    #1 9 inches
    #2 8 3/4 inches
    #3 9 inches
    #4 8 3/4 inches

    Clean power from 1000 rpm to 8800

    all for fuel adjustment screws are between 2 and 2 1/4 turns from bottom .

    The bike never ran this good !!!

    Russ
    Canton, PA
    85 XJ700N
     
    Redman276, May 6, 2008
    #5
  6. MiCarl

    MiCarl Active Member

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    Your units must be wrong. MM HG mercury perhaps?

    Every XJ I've synced ran about 5" water of vacuum.
     
    MiCarl, May 6, 2008
    #6
  7. Redman276

    Redman276 New Member

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    yea i went by inches this time , and yes i am puzzled why im in the 8 -9 inch range , but after i was done with the 700 , i did a 79 XS 750 tripple, and reset all hsi carbs to 6 inches , and wow what a difference .

    so i went back to mine and checked #2 for reference , 9, balanced 3 with 4 , 8 3/4 across then 1 ,2,3, 4 and anything below 8.5 and my bike doesnt run ......

    could something be wrong ????
     
    Redman276, May 9, 2008
    #7

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