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  1. #1
    Gold Member mik's Avatar
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  2. Default bike running rough, coughing, feels like misfires

    So several weeks ago I noticed my bike was running rough. (Xb12stt) checked primary fluid, adjusted primary, changed oil (was due anyway). No change. It started to get worse and so bad that I actually turned around and went home to get my car for commute one night.

    Combustion requires Fuel Air Spark Timing. I've heard that acronym somewhere. I prefer FACTS, Fuel Air Compression Timing Spark.
    I had no reason to suspect fuel, so I moved on to air. No reason to suspect air as the filter was good and there were no obstructions, timing hasn't changed so I'm good there. Spark. Decided to check my plugs. While doing some research I found on 'the other site' this thread. Seems these bikes have poor ground issues at times. I never bothered checking compression because the plugs looked pretty worn. I saw no aluminum deposits, oil, soot, cracked electrode or anything that would cause me to believe there might be a compression issue.

    When I went to inspect the plugs, I pulled the coil pack too. The threads on the mounting bolts and the coil pack bracket had a lot of oxidation. The plugs looked kinda rugged, very worn. I used brisk 10zs plugs and the rings of electrodes were worn back into the ceramic, making it look ridged, not like a cone like when brand new. I suspect this is part of the issue too.

    I will have to look up how many miles are on the brisk plugs. I don't think they look bad like I'm running lean or something, and the bike rarely gets even to 200 so I don't think I'm overheating the plugs. Ill post pics of the plugs later.

    I ended up getting some cheap champion 905 copper core plugs. Gapped to thirty five thou. Cleaned and coated the pack mounting bolts with dielectric grease and made a ten gauge ground cable from pack bolt to negative battery terminal.

    I'm hoping for a marked improvement.
    Last edited by mik; 06-16-2015 at 06:44 PM.

  3. #2
    Gold Member mik's Avatar
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  4. Default

    I had approximately 32k miles on the bike when I installed the Brisk BR10ZS plugs. It is just over 40k miles now. For 40 bucks shipped, that's not a viable option for plugs for me. The normal service life of the harley 10r12a plugs is approximately 10k miles too. I'll stick with the cheapies. Your mileage may vary, but that's what I'll be doing. I was unable to determine if the Brisk plugs made a major difference for me as I had an intake manifold seal leak that I fixed with new seals at the same time. It definitely ran better but I don't know if it was the plugs or the seal leak being fixed. For 2 bucks a plug for champions, even if I have to check/gap/possibly replace every 5k miles at my oil change that's ok with me.
    Last edited by mik; 06-16-2015 at 06:46 PM.

  5. #3
    Gold Member mik's Avatar
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    I can't see. To post the pics I took on my phone to the thread. Oh well.

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  8. #5
    Gold Member mik's Avatar
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    Quote Originally Posted by ezblast View Post
    A TPS reset is needed?
    EZ
    I don't see why, it still idles at 5.5 for the tps value. I've reset it probably three times since I've owned it for various reasons. I know you're trying to cover all bases, but what makes you think it'd be necessary? Are you saying that's the cause of my problem or after my fixes I should reset?

  10. #6
    Super Moderator ezblast's Avatar
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  11. Default

    I know when stuff goes wonky that is the first thing to do/check - like on a Blast you would check the intake coupler.
    EZ

  12. #7
    Gold Member mik's Avatar
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    OK. I didn't reset it because I didn't want to introduce too many variables. Rode it today much better. Smoother idle. Only a couple hiccups not nearly as rough. Before it was hiccups every couple minutes. I may reset tps but not yet.

  14. #8
    Gold Member mik's Avatar
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    So I don't know WTF. Like above I rode it during the day, it was 80-90* out. Rode it that night and the misfiring/hiccuping was terrible. I had to limp home again. It really felt like it was a ground cable that was coming loose or something.

    I decided after that to clean the grounding cables, etc.

    So I removed the main ground from the battery, wiped it down, and retightened. I also disconnected the TPS sensor and ECM harness to test continuity for the sensor ground. I tested continuity for system ground to ECM as well. I don't know why, but I did not test continuity through the harness for the ECM to coilpack ground. However, I did add that new ground strap directly from the coilpack. Ground strap was added post issue to try to fix the isssue, so it did not start the overall issue.

    Couple days ago, after cleaning it all up, I went on an afternoon ride in the 95* heat and rode the heck out of it. Datalogged to and from town. I felt maybe a couple hiccups. Overall quite rideable.

    Decided to ride it to work this morning. Temps outside were like 70-80*? Bike felt great the first half of the commute, then halfway through it started to hiccup again. Not as bad as before, but really disconcerting. The RPMS and the Speedo would both drop significantly when it hiccuped. Like an electrical disconnect and the needles were just turned off for a fraction of a second.

    Ride home, ambient temps 102*+. Had some hiccups in the first half of the commute, but not bad. Second half was great, I don't remember any hiccups.

    Attached you will find my ecmdroid datalog files. They are appropriately named with dates, times, and descriptions of stuff.
    In megalogviewer I graph RPM, Load, AFV, CLT, Speed, Time (to make sure datalogging is contiguous).


    The 'hiccup' is evidenced when the RPM (and Speed to a less obvious extent) is proceeding normally when it suddenly drops to about half of its value. When you find that datapoint, you can zoom in and see the matching speed hiccup. I can't find an associated sensor value you like CLT or load that screams at me, "hey, your [TPS/ETS/IAT] is fried!".


    Opinions? Clean grounds again, Rinse, repeat? I doubt a TPS reset would help.
    I want to say the coil pack is on its way out, but I've had that issue before and the bike ran way more rough all the time, not just random hiccups. The pack was replaced after that (clearly).

    However, I don't think a failing coilpack would cause the speedo reading to drop like that. And although the hiccups are rather rough, they are not so rough that my speed drops from 67mph to 54mph in 0.33 seconds. If you doubt that, I'm gonna drop some math on you. 67mph = ~30m/s. 54mph = ~24m/s. 30m/s-24m/s = 6m/s. 6m/s decel in 1/3 of a second is 18m/s^2. That's nearly twice the force of gravity. I did not experience that level of deceleration.


    http://www.kokkenhukerracing.com/upload.zip

    Also, umm, speeds registered in the datalog are actually in km/h, not mph, and thus are not over the actual legal speed limits. Just FYI.
    Last edited by mik; 06-27-2015 at 12:39 AM.

  16. #9
    Gearhead crazysycodude's Avatar
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  17. Default

    I am actually starting to think it may be the ignition because your symptoms are so random and it matches what mine was doing

    Sent from under the Blast

  18. #10
    Gold Member mik's Avatar
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    Quote Originally Posted by crazysycodude View Post
    I am actually starting to think it may be the ignition because your symptoms are so random and it matches what mine was doing

    Sent from under the Blast
    OK, so how does that explain the speed reading drop?

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