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Seems to be running lean

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  • Seems to be running lean

    i have a 2008 xb12 stt 100% stock with 8000 miles I'm the third owner and have had this problem since I bought it.

    When i start the bike cold it fires immediately as intended, idles for roughly 15 seconds then starts surging and eventually stalls. When it is surging if i give it a shot of fuel through the intake it smoothes out for a little bit then repeats the surge/stall process. My first instinct was a vacuum leak, checked none found, replaced intake seals anyways, no change. I've done the tps reset also with no change. I had the dealer update the ecm because I noticed the fan running while stopped and knew there wasan update for that. well after the reflash the bike seemed to run much better for the next couple of days then started having the same issues. After the bike warms up it will idle ok but seems to have low power and flat spots in the power curve. I'm positive it's not recievig enough fuel but I don't know why. Oh and I've checked fuel pressure even while riding it and 50psi all day long. I have no access to ecm spy or any other software at this time and my local hd dealer is not competent enough for me to trust them. I apologize for the long first post, but I haven't been able to figure this out any help would be appreciated.

  • #2
    Have you checked your head gaskets as it sounds to me like you might have a head gasket that is starting to fail.
    Bonneville might have beat us again this year but that White Bitch is going down in 2018!!!

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    • #3
      Thanks Dan! You think head gasket with that low of mileage? What's going to be the best way to check them aside from just a visual inspection? I've gotten pretty frustrated with this and have actually ridden it this way for about 5000 miles thinking eventually it will get worse and maybe become more obvious as to what is wrong. It never gets any worse it's very consistent i even took it on a 1500 mile trip once.

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      • #4
        that doesn't sound like head gaskets then as they get worse pretty quickly.

        Have you ever had it on a dyno with a sniffer to just confirm if it really is lean and at what rpms? Might be worth it to really find out
        Bonneville might have beat us again this year but that White Bitch is going down in 2018!!!

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        • #5
          I have not done that and it's not so easy to do around these parts, but I do know a couple of places that might be able to handle it. It's most certainly lean on cold start up because as long as i keep a steady trickle of carb cleaner or some other fuel going into the intake, it stays running smooth. I am an auto tech by trade and although this is not a car an engine is an engine and i do know characteristics of a lean afr. Would the dealer reflashing the ecm have reset the fuel map back to the stock configuration in the event that a previous owner had altered it in a bad way? The reason i ask is because it did run pretty good for a couple of days after the dealer did an update on the ecm.

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          • #6
            If it was me I would get a new "race" ecm from IDS. I sell them for $310 shipped to US addresses and it will set it to a much richer tune which will give more power and the bike will run cooler.
            Bonneville might have beat us again this year but that White Bitch is going down in 2018!!!

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            • #7
              Does that motorcycle have a idle air control valve/motor. My truck did the same thing awhile back, it didn't throw a code, turns out the idle control valve/motor air passages can get clogged and that screws up the reading to the sensor. I think they call it an air idle control something.

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              • #8
                Far as a head gasket, you can actually hear that with a stethoscope, or your ear if it is bad.

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                • #9
                  You could just sell that and get a carbed bike with ecm and map sensor. Easy peasy then. I hate electronics; Just more shit to go bad.

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                  • #10
                    Well I decided not to replace the ecm, but rather to download ecmspy and review the live data. After getting connected to the bike I immediately noticed an odd fluctuation with the tps (about a 2* variance) not much, but enough to cause a bunch of fuel delivery problems. I replaced the tps, the fluctuation was gone and it ran 100% better, but still not quite right. After some researching the settings in the ecm i decided there was a problem, but didn't know how many changes had been made so I got a stock eeprom file from a member of another forum and installed it now it runs perfectly.

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