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Question Regarding "High RPM" Sync

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  • #1

    Question Regarding "High RPM" Sync

    So, the GSX1100 uses flat-side CV carbs. Not that it makes a difference, but just a note. Forum members on there are relatively young in age (first-time bike owners), so the collective knowledge does not have the experience like our forum.

    So, there are literally 12 pages of threads regarding syncing the carbs. However, contrary to our "low idle" sync, their recommendation is for a higher idle sync. Their response as-to why:
    "it is mid point on the idle circuit. it has a higher vacuum reading, making the sync more accurate as rpm will fall or rise as the adjustment is made. Too low of an rpm and the readings are too low to get even precisely and could stall the bike. There are many ways to do a sync, I sure. This is the way I and many Kat owners do a sync with a column type sync tool, which is another reason, they need more vac to pull to mid point on the scale."
    1979 XS1100F
    2H9 Mod, Truck-Lite LED Headlight, TECHNA-FIT S/S Brake Lines, Rear Air Shocks, TKAT Fork Brace, Dyna DC-I Coils, TC Fuse Block, Barnett HD Clutch Springs, Superbike Handlebars, V-Star 650 ACCT, NGK Irridium Plugs, OEM Exhaust. CNC-Cut 2nd Gear Dogs; Ported/Milled Head; Modded Airbox: 8x8 Wix Panel Filter; #137.5 Main Jet, Viper Yellow Paint, Michelin Pilot Activ F/R, Interstate AGM Battery, 14MM MC, Maier Fairing, Cree LED Fog Lights.
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  • #2
    What I do is adjust the sync at about 1000 to 1200 RPM, and then rev it up to 4,500RPM and let it settle then check to see that all 4 are still in line. The low RPM sync is NEEDED to get the bikes to run as they should, and the midrange sync is a sanity check on the overall condition of the carb sync.
    Ray Matteis
    KE6NHG
    XS1100 E '78 (winter project)
    XS1100 SF Bob Jones worked on it!

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    • #3
      Originally posted by DiverRay View Post
      What I do is adjust the sync at about 1000 to 1200 RPM, and then rev it up to 4,500RPM and let it settle then check to see that all 4 are still in line. The low RPM sync is NEEDED to get the bikes to run as they should, and the midrange sync is a sanity check on the overall condition of the carb sync.
      Agreed! Should still be close in mid to higher rpm.

      If they are having that much trouble getting a vac reading down low then they must have other issues.
      Nathan
      KD9ARL

      μολὼν λαβέ

      1978 XS1100E
      K&N Filter
      #45 pilot Jet, #137.5 Main Jet
      OEM Exhaust
      ATK Fork Brace
      LED Dash lights
      Ammeter, Oil Pressure, Oil Temp, and Volt Meters
      Green Monster Coils
      SS Brake Lines
      Vision 550 Auto Tensioner

      In any moment of decision the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.

      Theodore Roosevelt

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      • #4
        Originally posted by natemoen View Post
        ... If they are having that much trouble getting a vac reading down low then they must have other issues.
        +1! What Nate and Ray said!

        .
        -- Scott
        _____
        ♬
        2004 ST1300A: No name... yet
        1982 XJ1100J: "Baby" SS Brakes, '850 FD, ACCT
        1980 XS1100G: "Columbo" SS Brakes, '850 FD, ACCT
        1979 XS1100SF: "Bush" W.I.P.
        1979 XS1100F: parts
        2018 Heritage Softail Classic 117 FLHCS SE: "Nanuk" It's DEAD, it's not just resting. It is an EX cycle.
        ♬

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