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Mriulvr
Posted on Monday, July 01, 2019 - 04:35 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

04 Buell XB12s 47.5k well maintained (i.e., preventative maintenance) since I bought it eighth years ago. Garage kept, daily driver with a few long trips, never tracked or abused. Only issues I have had are the relays (see #9 below), clutch ramp broke and repaired, and the infamous 77 connector problem (I think that is the right one). Replace handlebars about five years ago after someone apparently knocked it over in the parking lot and bent the bars, replaced the Jardine exhaust with a Hawk and tuned, tail chopped and put in an XBLight integrated tail light, and breather reroute.

The tach works about half the time while riding. The other half it bounces around between a few rpm high to 3000 rpm high but not while idling or reving in neutral. It started after doing accelerations at each throttle position with wideband O2 sensor when tuning. Does it whether on the wideband or NB and was fine before that while using the LC2 O2 sensor. Nothing was changed or modified before it started. I have troubleshooted everything I can find (on this forum and others, manual, wiring diagrams, etc.) and can think of so I am hoping someone has an idea I haven't considered. What I have done so far.

1. Checked logged rides and RPM is normal, doesn't show the bouncing that the tach shows,
2. Checked wiring for any bad insulation/exposed wires,
3. In the process re-ziptied wiring,
4. plug wires are only about a year old,
5. spark plugs are new (started prior to new plugs),
5. cleaned connector to coil (I understand the tack is determined by the coil) as well as pretty much all other connections,
7. I cleaned and treated all earthgrounds (https://www.buellxb.com/forum/showthread.php?54706 -Fixing-Earthing-Problems-Why-and-How) including adding the ground from the battery and to the coil,
8. Battery is good and connections are tight and clean,
9. Had a relay that was going bad so replaced all three.
10. Checked and cleaned or replaced fuses and the fuse box connectors while cleaning the earthgrounds.
11. Checked and re-siptied wiring under the airbox, thinking I might have some RFI interference.

The tach works fine while idling so do a wiggle test of the wiring doesn't seem like it will help. I am starting to wonder if it is the tack itself or an exposed wire somewhere that I haven't found.

Anything else anyone can think of?
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Tpehak
Posted on Monday, July 01, 2019 - 06:33 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

You can check if tachometer signal is good with oscilloscope on the tachometer signal wire from the cluster plug.

So if Bluetooth dongle shows correct RPM with no bouncing it means the ECM has correct RPM signal.

RPM signal to cluster goes from ECM (at least on 2009 Buell XB, so check wiring diagram). So it is might be bad ECM too.

If you see bad signal on cluster plug you can connect oscilloscope to RPM output wire on ECM plug and see the signal there. If the signal on ECM plug is good it means the problem is the wire. If bad it means the ECM is bad. If the signal in the cluster plug is good it means the problem is likely inside the cluster, or on the cluster ground wire.

(Message edited by Tpehak on July 01, 2019)
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Mriulvr
Posted on Tuesday, July 02, 2019 - 03:10 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Tpehak, thanks.

First, besides not having an oscilloscope, that would be hard to do when on a ride, which is when the RPM issue occurs.

Second, what wood a "good" signal look like and what would a "bad" signal look like? I found the hertz for the speedo in the manual (7-56) but nothing for the tach. I have also not had a 35 error code for the tach, that I know of and I did check. The manual says to use the Digital Technician (Part No. HD-44750) to test the tach but I am not too enthused about the idea of an HD tech touching my Buell.

I will take a closer look at the pink wire from the ECM to the tach and the connections at both ends again.
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Tpehak
Posted on Tuesday, July 02, 2019 - 03:50 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

You can buy digital tachometer on eBay for $5-$10 and connect it to the tachometer wire. If it works OK the problem is likely in the cluster. If it works the same the problem might be ECM.
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Mriulvr
Posted on Wednesday, July 03, 2019 - 01:41 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

So I started thinking on my ride home yesterday, which is scary in and of itself. I have gone through the electrical system, checked, cleaned, and treated all the earthgrounds and nearly all the connections...except the ECM! So last night I pull into the garage, pop the seat, remove the ECM connections, spray liberal amounts of CRC 2-26 into the ECM sockets and each of the holes for plugs, let it sit for a little while and do its thing, clean up excess, and plug them back in while still wet. Then I did the same to top of the plugs, where the wires go in.

Today I am on the way to work and tach seems to working fine then starts the bouncing again, but not as much, then the tach settles in and no bouncing for the remaining 30ish miles of my 35 mile ride.

Hoping I didn't just jinx myself, but looks promising or at least was a part of the issue. I hate electrical gremlins.
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Mriulvr
Posted on Sunday, August 04, 2019 - 01:38 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

So, apparently did jinx myself with the last post. Tach still bounces, and sometimes sits at 0 RPM, and at other times works fine. Thinking of opening up the dash and trying to clean with electronics cleaner. As I previously posted, the RPM output from data logging is correct so it doesn't seem to be the ECM output. The only other thing I can think of is the spark plug wires are bad, but they were replaced with new one last year and the plugs this year.

Doesn't seem to be an issue other than annoying but is now a driving me nuts and I am taking it as a personal challenge.

If anyone has any other ideas from what I have done, see previous posts, I would be glad to hear them.
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