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Thread: Very noticeable flat-spot/sputtering in power-band between 4-4.5krpm

  1. #11
    Junior Member Polishblood's Avatar
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    Quote Originally Posted by 34nineteen View Post
    Your first step would be to get a service manual. Being that you asked if the motorcycle has 2 sets of injectors per cylinder tells a lot.

    And yes, it does sound like the 2nd set isn't kicking in and the sensor probably needs to be recalibrated using dedicated service equipment. There are actually 4 sets of injectors per cylinder. The first set does idle to 1500 rpm, the second covers 1500-3000, the third covers 3000-4500 and the 4th set covers 4500-redline. On the 1125's all the injectors kick on at once, which is why they make so much more power than an XB.

    For someone who wants to fix an issue "immediately", you're are going to wait until "tonight" to look into diagnostic tools? Is Bridgewater in Hawaii?

    Start your diagnosis here... www.buelltooth.com. Tell him Cooter sent you, not me...
    Quote Originally Posted by lunaticfringe View Post
    check once more for historical fault codes. if you find one or more in the "50 series" it's a failing ECM. before replacing check the dedicated ECM ground wire for integrity and continuity.
    otherwise...classic failing fuel pump. service it.
    Thank you for the detailed information gentlemen. I just ordered the BUELLtooth ECM Interface off of www.buelltooth.com. I look forward to using it and hopefully it comes in sooner than later. I will keep you guys updated with any information/questions I may have.

    Lunaticfringe, with regards to Buells, does a classic failing fuel pump exhibit a dip in power at 4,500 rpm?

  2. #12
    Senior Member Cooter's Avatar
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    In stock form these have a slight dip in mid-range power you can see on a dyno chart. Its not as extreme as you describe though.
    Yes. High load/high RPM put a strain on a fuel pump and will expose a weak one. Easy swap, and Lunatic has the stuff if you need it.

    IMO, I wouldn't start guessing quite yet. Wait for the diagnostic device to show up and use it to narrow down the causes. Unless you like frustration, expense, and added time? Lol, keep us posted.

  3. #13
    Junior Member Polishblood's Avatar
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    Screenshot_20200414-110058_EcmDroid.jpgScreenshot_20200414-110124_EcmDroid.jpgScreenshot_20200414-110355_EcmDroid.jpg

    I read in the electronic diagnostics manual that an oxygen sensor reading below <0.41 indicates a lean mixture and a reading of >0.56 indicates a rich mixture. I have no clue if I am using ECMdroid correctly however I had my bike idling and the O2 sensor reading was fluctuating between 0.1-0.7. Therefore I couldn't accurately tell where the average reading was. ALSO forgot to mention that my exhaust does smell like gas which correlates to a rich mixture (AFV of 0.82%). However last time I checked my spark plugs, they were white with a hint of browning (they did not look flooded at all). So I am baffled. I will check my plugs again.

    Using ECMdroid I performed a front and rear injector test. When performing the front injector test, I heard 5 sequential taps. (tap tap...tap tap...tap). When performing the rear injector test, I heard 5 taps in the same manner as the front.

    Questions:

    Is there a list of what all data variables in ECMdroid mean/are testing? Also is there a normal value list for the variables? For example, I don't know the difference between "02" and "021"... or if "inj1 ADC" is suppose to read 0 while the bike is running.

    Are there any tests in ECMdroid that you guys recommend I do?

    How can I further check my injectors? Perhaps only the 4th set of injectors are not working properly, therefore tripping the low AFV (rich mixture) and not showing any symptoms of flooding at the plugs. I don't know. Kind of baffled.
    Last edited by Polishblood; 04-15-2020 at 12:15 AM.

  4. #14
    Senior Member Cooter's Avatar
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    What is the problem you are trying to find?

  5. #15
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    So I went for a ride today and my bike started doing this exact thing at the same rpm. This is just theory but isn't this the point at about 4.5 rpm under 50 to 75% throttle the mapping exits out closed loop learn to open loop? If the mapping was heavily altered in the closed loop learn would that difference transitioning to open loop cause the blip? Anywho, I reflashed the stock race map to see if that was it. Won't know till I take it out for another ride.

  6. #16
    Junior Member Polishblood's Avatar
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    Quote Originally Posted by Jonus View Post
    So I went for a ride today and my bike started doing this exact thing at the same rpm. This is just theory but isn't this the point at about 4.5 rpm under 50 to 75% throttle the mapping exits out closed loop learn to open loop? If the mapping was heavily altered in the closed loop learn would that difference transitioning to open loop cause the blip? Anywho, I reflashed the stock race map to see if that was it. Won't know till I take it out for another ride.
    Yea, my theory as well. During closed loop, the oxygen sensor is compensating for a problem. Since the AFV is significantly different between closed and open loop, I am noticing a blip or hesitation in power.

    My AFV was 82%. So the oxygen sensor is sensing a rich condition in the exhaust and is compensating for it by adding less fuel. So what's causing the rich condition? I don't know however I just checked my spark plugs. Front spark plug looks light tan all around. Rear spark plug looks 50% brown and 50% white/barely tan. So front looks slightly lean but ok and rear looks like it's experiencing both a lean and rich? (will post pictures of plugs soon). The rear plug correlates to the oxygen sensor since the oxygen sensor is located on the rear exhaust.

    If I saw that my plugs, especially the rear one, were bone white (indicating an obvious lean mixture) and my oxygen sensor was reading rich, I would definitively diagnose my problem as having a faulty oxygen sensor. That is not my case however I am not excluding my oxygen sensor just yet.

    I switched the plugs again, this time from the NGK DCPR9EIX, which EVERYONE recommends, to the OEM spark plugs which are called 10R12X (part number 27794-08). These OEM spark plugs are advertised foul resistance. I felt a difference. From 0-3krpm, the bike seems less powerful (in fact I almost stalled twice the first ride) however acceleration feels smoother throughout the entire rpm range (less cammy). Also, the 4.5krpm hesitation happens ALOT less. It use to happen 80-90% of the time when hitting 4-4.5krpm, now it happens only 5-15% of the time.

    I checked my AFV with buelltooth after switching the plugs back to the OEM. AFV was 82% and now it is 90%. I still don't think I fixed the problem. I ride at an altitude of only 150 feet above sea level. I believe my AFV should be above 100% or at least near 100%. i will write up another post below explaining what I think the problem might be.
    Last edited by Polishblood; 05-23-2020 at 05:45 PM.

  7. #17
    Junior Member Polishblood's Avatar
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    Left spark plug in both pictures is the front spark plug. Right spark plug in both pictures is the rear spark plug.
    IMG_7031.jpgIMG_7032.jpg

  8. #18
    Senior Member Cooter's Avatar
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    Plugs look good. How does it run when you re-set the AFV to 100?

    Still just totally guessing... but you could have an old/fouled/lazy O2 sensor.

    and I never recommend this, but you could save your existing .xpr file with ECMDroid and try a new stock program. I don't know any history of your bike, so I don't know if it's a stock program or if you have been messing with it, but an overly rich condition that the ECM is trying to correct is common with all that.

  9. #19
    Junior Member Polishblood's Avatar
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    So as mentioned before, I installed the OEM spark plugs and the bike's main symptom, hesitation between 4-4.5krpm, was significantly reduced. Occurrence dropped from 80-90% to 5-15% of the time. AFV is now 90% vs 82%.

    I normally road the bike on and off for the past 2 years. After recently riding the bike for about 200 miles I noticed a couple more symptoms. None of these symptoms are new but I never paid attention to them because they were not noticeable. After installing the OEM spark plugs, which seemed to make the bike accelerate more smoothly, some of these symptoms became more noticeable. I will list everything below.

    List of all symptoms (revised after installing OEM plugs)

    1. 4-4.5krpm hesitation occurs less when riding briskly (exact opposite with old spark plugs). Hesitation does not occur when the bike is cold.
    2. Strong smell of gas when parked after ride
    3. Very slight bucking at various rpm between 2k-4.5krpm (closed loop).
    4. Idle sways between 1-1.2krpm after cold start, levels out after 10 seconds (is this normal?)

    Possible Problems

    1. Faulty oxygen sensor (however plugs show overall good burn)
    2. Faulty Fuel Injectors or O-rings leaking

    I ordered both an OEM oxygen sensor and fuel injectors w/ intake seals. I already did the service manual fuel injector test (ignition on and off 5 times to build fuel pressure). The fuel injectors are dry. I have a feeling the leaking only starts when the bike is warm. I can test that out. Checking the injectors with a mirror after coming back from a ride.

    Questions:

    Do I need to remove the throttle body to replace the fuel injectors? Any advice on replacing the injectors?

  10. #20
    Junior Member Polishblood's Avatar
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    I have yet to set the AFV to 100. How long will the AFV stay at 100 if I don't disable closed loop? I'm shying away from saying it is the oxygen sensor because it appears to be doing its job. Plugs look relatively good.

    I think it maybe the fuel injectors or o-rings around them that are leaking at higher temperatures.



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