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Thread: XB9r Afterfire and AFV issues

  1. #1
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    XB9r Afterfire and AFV issues

    Hi I'm pretty new to this forum and have been lurking for the better part of a year and I have finally broken down to ask for help. I have a 2003 XB9r that I bought used about a year ago with 25k on it. I bought it cheap knowing it would be a project and that turned out to be true.

    As far as the afterfire goes I know I have read that it is pretty common with these vtwins but my bike sounds like an ak47 when Im coasting. I have a Feeling that this has to do with the AFV being so high and its getting way to much fuel but I am not sure

    As for fixing the AFV right now it goes between 116-120%. I have not added any mods to the bike, I bought it with a k&n filter and jardine exhaust already installed. The previous owner had also done a breather reroute. I changed the bike from the stock tune to the race map but that did not change my afv problem. I replaced the intake seals after doing a leak test and Im not 100% if they are seated correctly and have purchased a set of james ones to install this week. Hopefully that will fix all my issues but I am looking for some other advice on what my problem could be. Thank you! sorry in advanced also, I am not very technically inclined and I may ask a few dumb questions
    Last edited by BigWhale; 01-11-2020 at 03:14 PM.

  2. #2
    Senior Member Cooter's Avatar
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    Hello Big Whale and welcome to the forum

    You are describing symptoms of being lean, but the AFV you posted shows rich, so I'm confused.
    Lets try one at a time.
    The AFV is how the ECM adjusts to current conditions. While it is a little high (rich) it's not a "problem" at 116-120.(EDIT: I had it backwards, that AFV is LEAN, brainfart sorry)
    Does it run well besides the decel popping?
    Are you sure the map is a "BUELL Race Map"? Where did you get it?
    If you test the intake seals again, that would tell you if they are seated properly.
    Good luck, post up what you find.
    Last edited by Cooter; 01-12-2020 at 06:30 PM.

  3. #3
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    The bike runs well and it does not get hot like it would if it was lean. I have been running logs with Buelltooth and looking at them on megalogveiwer just to get an idea of running temps. Also I got the racemap from this site - https://sites.google.com/site/ecmspy/home

    I did a the intake test again today, first when I started it up before riding and also when I got back from about an hour ride. It was fine when I left but when I tested it when I got back the rpm's increased so I am assuming that's where my problem lies?

    Also I thought that the AFV being that high was a problem? From what I read before anything over 110 was bad. I know every bike is different but is that not the general rule of thumb?

  4. #4
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    Also thank you for welcoming me! You guys all seem super helpful and kind on this forum

  5. #5
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    I don't know jack but is your intake horn installation correct. Mine wasn't and the bike had symptoms like you describe.

  6. #6
    Senior Member pdksh's Avatar
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    The AFV increases to address a lean condition. Its adding 15% to 20% more fuel to. Compensate for a lean running engine. Excessive back fires during deceleration also indicates a lean condition. Id be very suspicious of your intake gaskets. They get hard and allow extra air, causing, you guessed it; a lean condition. Very easy to test with a can of carb cleaner. Twin motorcycles has a video or two. Could also be a bad O2 sensor.

  7. #7
    Senior Member BuellyBagger's Avatar
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    I did a the intake test again today, first when I started it up before riding and also when I got back from about an hour ride. It was fine when I left but when I tested it when I got back the rpm's increased so I am assuming that's where my problem lies?
    You probably found your issue. The two bikes I've had to do intake seals on have shown symptoms when the were cold and then got better as they warmed up, but that's not to say it couldn't go the other way. Checking out your velocity stack installation before you go any deeper is good advice, as what ever you were using to spray for your gasket test could've snuck into a poorly installed air horn/velocity stack too.

    I will also add that if you remedy your wandering afv and still have decel pop that I've found that having a properly set TPS (with a nice clean throttle body) and then setting the idle as low as safely possible (within the recommended rpm range of course) can clean up minor decel pop.
    Last edited by BuellyBagger; 01-12-2020 at 03:27 PM.

  8. #8
    Senior Member Cooter's Avatar
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    I edited my post, because I'm an idiot and had it backwards (AFV). All these guys are right about it being lean, and checking that the intake horn is sealed to the airbox base is a great catch from outthere



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