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Thread: 03 Xb9s 70mph issue

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  1. #1
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    03 Xb9s 70mph issue

    Hey all,

    I just went on about a 28 mile round trip mostly highway and on the way there I got up to approx. 80mph with no issues. I stopped at my destination for only about 5 minutes.

    On the return trip when I accelerated up to around 70-73mph the bike sputtered pretty bad and would continue until I slowed down to under that 70mph range. I tried to accelerate back up to around that 70mph range several times on the remainder of my trip with the same outcome. Even downshifted into 4th and the issue was still there. Also tried riding in 2md gear at 4000rpm (what 5th gear is at while doing 70mph) and no issue. I have a battery voltage gauge in the cluster and it fluctuated between 13.7-13.9V during this time.

    Any idea what this could be? Obviously it is load/speed dependent.

    Edit: I have nearly a full tank of gas (Shell) and also have the RSS with ambient temperature of 72F so it wasn't an overheating issue. The fans do work fine I confirmed

    This is the first time I got up to these speeds since last riding season (9 months ago)

    2003 XB9SL
    17,xxx miles
    Hawk exhaust with race tune
    Oil change 1 month ago and I verified fill level is correct

  2. #2
    Senior Member Cooter's Avatar
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    Paging Lunatic with an instant fuel pump diagnosis using ALL CAPS!!



    Lol, He could be right ya know. He stocks the parts for a re-build and whole new assemblies he gives a great deal to forum members too!

    It could be lot of things (seriously fuel pump is one of them) but you will need some tools and technical skill to diagnose it properly instead of guessing and throwing expensive parts at it until you are so frustrated you sell your beautiful Buell

    No offense but I'll assume your skill is not much more than oil changes, because you went right to the forum to ask for guesses from strangers that have never seen your bike... instead of your toolbox NO one here knows what's wrong with your bike
    We will need you to help us diagnose it first.

    May I suggest to at least download ECMDroid (free on google play) you will need to get a bluetooth dongle that lets it communicate wirelessly to your ECM. I like mine from Buelltooth.com

    ECMDroid can tell you if it is running rich or lean, electrical problems, sensor problems, and yes install fuel tables as well. *Please DO NOT assume ECM 'tuning' is at fault and go down that rabbit hole!

    You can also get a free .pdf download of the factory service manual from Buellmods.com or Buelltooth.com.

    You will need a 50psi pressure gauge and a Buell specific 'tee' for the fuel line before you can test for fuel pressure. ECMDroid won't do that.

    Or find a decent V-twin mechanic familiar with Buells or Sportsters.

    Good luck buddy, I'll keep an eye out on this thread and help if I can
    Last edited by Cooter; 07-17-2019 at 12:15 AM.

  3. #3
    Junior Member
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    Quote Originally Posted by Cooter View Post
    It could be lot of things (seriously fuel pump is one of them) but you will need some tools and technical skill to diagnose it properly instead of guessing and throwing expensive parts at it until you are so frustrated you sell your beautiful Buell

    No offense but I'll assume your skill is not much more than oil changes, because you went right to the forum to ask for guesses from strangers that have never seen your bike... instead of your toolbox NO one here knows what's wrong with your bike
    We will need you to help us diagnose it first.

    May I suggest to at least download ECMDroid (free on google play) you will need to get a bluetooth dongle that lets it communicate wirelessly to your ECM. I like mine from Buelltooth.com

    ECMDroid can tell you if it is running rich or lean, electrical problems, sensor problems, and yes install fuel tables as well. *Please DO NOT assume ECM 'tuning' is at fault and go down that rabbit hole!

    You can also get a free .pdf download of the factory service manual from Buellmods.com or Buelltooth.com.

    You will need a 50psi pressure gauge and a Buell specific 'tee' for the fuel line before you can test for fuel pressure. ECMDroid won't do that.

    Or find a decent V-twin mechanic familiar with Buells or Sportsters.

    Good luck buddy, I'll keep an eye out on this thread and help if I can
    I have the ECM cable and the PDF. I am pretty familiar with the bike and able to do the diagnostic work on my own but the pdf does not specifically call out this issue nor have I triggered any DTC's. What I find most troubling is that it is ONLY between 70-73mph. I ride it a few times a week on my commute where the speed limit is 45 and never have this issue. Even with stop and go on the way home in 85*F weather.

  4. #4
    Junior Member
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    Hey all,

    I have bought a fuel pressure kit and verified it is within 49-51psi (might be 48 as the needle jumps a bit). Any other ideas?

  5. #5
    Senior Member Cooter's Avatar
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    Does it have 49-51 Psi at 70 mph?

    Use your "ECM cable" to check your current AFV. That will help diagnose whether it is a fuel, spark, or air, issue and give some clues here to help us do more than guess.

    "The answers you get can only be as good as the questions you ask"
    Last edited by Cooter; 08-27-2019 at 02:21 PM.

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