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Thread: Spastic tach

  1. #21
    Senior Member Cooter's Avatar
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    In the very beginning of your service manual:

    http://buellmods.com/content/downloa...ing_manual.pdf

    Page B-17

    Screen Shot 2023-01-07 at 8.12.04 PM.jpg

    The pink wire that drives the tach comes directly from the ECM.
    BECAUSE you said your bike runs fine while tach is spastic, all the signals TO the ECM are fine.
    the signals TO the ECM are fine.
    the signals TO the ECM are fine.
    the signals TO the ECM are fine.

    BECAUSE you said the speedo is NOT spastic at the same time, it eliminates any power or ground supply issue externally feeding the dash.
    it eliminates a power or ground supply issue
    it eliminates a power or ground supply issue
    it eliminates a power or ground supply issue

    SO

    You have an issue internally in the power or ground or signal to the stepper motor that the tach needle is on inside the dash. Replace it*.

    OR

    You have a intermittent open in the pink wire circuit that goes between the ECM to the dash. Replace it.

    Period.

    Screaming into the abyss




    * Buell XB mileage is held within the dash itself on a 'count-up' chip. So buy a dash with similar mileage.
    Last edited by Cooter; 01-08-2023 at 04:29 AM.

  2. #22
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    I have no idea what you just said. I'm here to trouble-shoot my Kawasaki.

  3. #23
    Senior Member mriulvr's Avatar
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    Cooter, thanks. That helps. I will try replacing pink wire first. If issue is stepper motor, may just live with it.

  4. #24
    Senior Member Cooter's Avatar
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    Or instead of hacking into a OE wire harness unnecessarily, use a DVOM to check continuity while wiggling the wires and connectors. Can't afford a DVOM?
    Heres a free one:
    Screen Shot 2023-01-08 at 1.16.42 PM.png

    If you can't find an issue there, it's the dash. Can't afford one?
    I'll send you the perfectly functioning guts of one to replace yours, for free. It's got about 32k on the Odo.

    PM me if you want it.

  5. #25
    Senior Member mriulvr's Avatar
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    PM sent
    Appreciate the coupon and offer on dash guts. Have a DVOM and checked continuity of pink wire. Will double check with wiggle test. Weird part is that it is inconsistent. When it does start spazzing it is after riding about 15ish minutes and then starts happening above 3kish rpm then calms down below 3k. Doesn’t flash a CEL, produce a code, or cause any noticeable issues other than my becoming OCD about it.

  6. #26
    Senior Member mmcn49's Avatar
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    Quote Originally Posted by Cooter View Post
    Or instead of hacking into a OE wire harness unnecessarily, use a DVOM to check continuity while wiggling the wires and connectors.

    If you can't find an issue there, it's the dash. Can't afford one?
    I'll send you the perfectly functioning guts of one to replace yours, for free. It's got about 32k on the Odo.

    PM me if you want it.
    I have an ongoing similar issue. Checked the wires, grounds etc and have found nothing.

    Where can you purchase a stepper motor?
    Last edited by mmcn49; 01-15-2023 at 10:12 PM. Reason: extra verbage

  7. #27
    Senior Member mriulvr's Avatar
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    Well, replaced the the dash guts with the one from Cooter. Took her for a ride and had the same issue although not as spastic as before. So, back to chasing a a wiring issue or a possible ECM issue. I did have a CEL after she had warmed up that only lasted about 20 seconds. Got back from the ride, connected ECM Droid, read error codes, and nothing showed up. This is driving me crazy.

  8. #28
    Senior Member Cooter's Avatar
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    Got a way to get a video?

    Will it do it in neutral?

  9. #29
    Senior Member Barrett's Avatar
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    Quote Originally Posted by mriulvr View Post
    Well, replaced the the dash guts with the one from Cooter. Took her for a ride and had the same issue although not as spastic as before. So, back to chasing a a wiring issue or a possible ECM issue. I did have a CEL after she had warmed up that only lasted about 20 seconds. Got back from the ride, connected ECM Droid, read error codes, and nothing showed up. This is driving me crazy.
    I did have a CEL after she had warmed up that only lasted about 20 seconds.

    There's your confirmation. CEL in conjunction with NO stored historical. CEL momentarily saw voltage or resistance activity it didn't like. Failing ECM. Mentioned this years ago.

  10. #30
    Senior Member mriulvr's Avatar
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    Quote Originally Posted by Cooter View Post
    Got a way to get a video?

    Will it do it in neutral?
    Have not had any tach issues in neutral. Typically only happens
    1. after riding for 10-15 minutes (possibly coinciding with engine getting to temp and ECM moving out of cold start enrichment?),
    2. Above 3k rpm, and
    3. Not consistently twitchy.

    Not sure if it is just differences between my original dash and the Cooter dash (differences in model or year), but the Cooter dash tach is less sensitive to small RPM changes. For example, at idle it sits steady at 1k while my original would be at 1k with very slight movements. Almost like the original was showing a continuous RPM feed while the replacement is sampling or disregarding small fluctuations.

    As for video, I might be able to set my phone up on my rammount so the camera captures the dash. Will have to check and might have to move it around to get it to work. If that works, I will get and share video as soon as I can.

    Weird that no error code stored. Wish I had been data logging to see what showed up. However, as mentioned a few posts back, I keep losing connection between my Buelltooth dongle and ECMDroid soon after starting a ride. Can’t figure out if this is a separate issue or somehow related to tach issue.



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