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Bigger mains + fairing + UNI = 4% more MPG

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  • Bigger mains + fairing + UNI = 4% more MPG

    I'm frankly amazed. Over the winter I added new butterfly seals, 140 mains (had 137.5's), an UNI filter and a spitfire fairing (like the rifle). I expected my MPG to drop. I used to get 40MPG. To my surprise, it went up.

    Yesterday I did my shakedown run prior to the XS East rally. Fxrer, five of his buddies and me did about 180 miles through the Lehigh valley on mostly twisty back roads. I did the last 50 miles home on the interstate, at about 70-75 mph, so it was a good mix of road types. I filled up at home and discovered that I got 44MPG. Go figure.

  • #2
    Randy,

    Glad to hear you made it back safe, and good news about the increase in mpg! That is a bit surpising. Maybe the group driving style was tamer than your norm?

    Have a good time on the Rally next weekend and be safe.

    Rick
    Rick
    '80 SG
    '88 FXR
    '66 Spitfire MK II

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    • #3
      Riding with a group (especially if you're not in the lead) you may be benefiting from a "draft". Also some fairings and/or windshields will create a more efficient airflow over the bike and rider. Now the wind isn't hitting the upper forktubes, gauges, your chest, speedo cable, clutch cable, brake hose, etc.
      Also with the increased main jets and filter the engine might be running more efficiently, not having to work as hard.
      All possabilities and they may all be wrong .
      Pat Kelly
      <p-lkelly@sbcglobal.net>

      1978 XS1100E (The Force)
      1980 XS1100LG (The Dark Side)
      2007 Dodge Ram 2500 quad-cab long-bed (Wifes ride)
      1999 Suburban (The Ship)
      1994 Dodge Spirit (Son #1)
      1968 F100 (Valentine)

      "No one is totally useless. They can always be used as a bad example"

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      • #4
        the engine might be running more efficiently, not having to work as hard
        Same reason you may get as good or better MPG with a V-8 over a V-6 in the same type of vehicle. Especially pulling a trailer.

        I also agree with the fairings helping, versus my body being a big &@% parachute sitting there in the wind without one. Plus... not nearly as many black specks in my teeth after a ride!!

        Tod
        Try your hardest to be the kind of person your dog thinks you are.

        You can live to be 100, as long as you give up everything that would make you want to live to be 100!

        Current bikes:
        '06 Suzuki DR650
        *'82 XJ1100 with the 1179 kit. "Mad Maxim"
        '82 XJ1100 Completely stock fixer-upper
        '82 XJ1100 Bagger fixer-upper
        '82 XJ1100 Motor/frame and lots of boxes of parts
        '82 XJ1100 Parts bike
        '81 XS1100 Special
        '81 YZ250
        '80 XS850 Special
        '80 XR100
        *Crashed/Totalled, still own

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        • #5
          I had the same results when I had switched winshields. My old one was destroyed in the accident, and I replaced it with a Nat'nl Cycle windshield with lower extensions. I used to get about 28 mpg at freeway speed, and now I am getting over 30 mpg.It must be the difference in the shape of the shield. The new one must be more aerodynamic.

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          • #6
            Surprised ... me too!

            Randy,

            I just filled up today, 169 mi, 3.08 gal = 54.8 mpg! Must have been the wind?
            Rick
            '80 SG
            '88 FXR
            '66 Spitfire MK II

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            • #7
              WOW!

              If we keep riding 339 all summer, think of the savings!

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