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Thread: Troubleshooting high AFV percentage

  1. #1
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    Troubleshooting high AFV percentage

    Ok Iím at a loss chasing a high AFV percentage.

    The bike is a 2005 xb12s with right at 11,000 miles. I bought it with a drummer exhaust and it has a race ecm in it, allegedly with a dyno tune. I have all the paperwork provided by the previous owner, but take that with a grain of salt I suppose.

    A while back I noticed it was starting to act as though it had an intake leak and I confirmed it with some carb cleaner testing around the intake seals. I bought a buelltooth and checked the AFV and sure enough it was 110%. I opted to pull the frame off the bike and check everything over while doing the intake seals. I decided to replace the plugs, wires, and clean off the grounding points while I was at it. Long story short I didnít install the seals properly the first go around and immediately had to redo my work.

    Everything is back together now and sealed properly. Iíve verified the intake seals with carb cleaner and a smoke system I have for checking for vacuum leaks. The TPS is set and bike runs and idles fine. For some reason the AFV percentage continues to sit around 110%. Iíve set it back to 100 and after a 50 mile ride it returned back to 110. I do have some popping on decel so Iím inclined to think the bike is in fact lean.

    I tested my fuel pressure and its sitting right at 51psi all the way up to 3000rpm. Iím sort of at a loss where to go from here. I could replace the O2 sensor but I donít think thatís the issue. Perhaps pull the injectors and ultrasonic clean them.

    Any thoughts on where to go from here?

  2. #2
    Senior Member Cooter's Avatar
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    Runs fine, a little decel pop is fine, 110 AFV is fine.
    Ride more, worry less


    Don't believe me?
    Internet rumors and old wives tales propagated by junior mechanics parroting bad info. Possibly a small leak in the exhaust.

    The factory set range of your AFV is 50-150. It is an ECM adjustment. Yes, it can be a diagnostic clue for a poor running motorcycle, but being in the center of an adjustment isn't 'better'. Let it do it's job. If it wants to sit at 110 and runs fine, let it sit at 110 and ride it.

    Want to replace the O2? Sure. It could be lazy after 18 years. Couldn't hurt.
    Want to clean the injectors? Sure. They get dirty in 18 years of service. Coudn't hurt.

  3. #3
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    Thanks Cooter. I guess I had just assumed that the AFV would have changed after fixing the intake seals so my brain started making a mountain out of a mole hill. It definitely increased on my first failed attempt at replacing them.

  4. #4
    Senior Member Cooter's Avatar
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    I understand the concern, and I would assume the same. BUT theres just so many reasons AFV will change, and 110 is really OK.

    Go ahead and do that preventative maintenance if you want too, your Buell will thank you with even more years of service Most of them live a pretty neglected life In fact my favorite babies have all been on the back end of a Tender for much too long, time for some fresh fluids and some exercise!

  5. #5
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    If you would stop drinking all of 34-19's beer, you would have enough time to take care of the babies.

  6. #6
    Senior Member Cooter's Avatar
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    You have a point
    But its BEER!



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