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Help me trace a wire (the adventure continues)....


Zero Knievel

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From http://www.cbr1100xx.org/forums/index.php?showtopic=86529

On another forum, someone suggested I check the harness side of the speed sensor to be sure my problem is indeed the speed sensor. If I'm not getting 5v on the supply going to the speed sensor, I need to find out why I'm not getting it in the first place.

So, I test it. 0.2v. Time to backtrack. I go all the way to the ECM. 0.2v. Now it gets fun. Nothing on the schematic shows what's IN the ECM, so I'm figuring (and hoping) that the power IN is on the same connector as the line coming out (gray).

I trace every wire that looks like it comes from the battery on switched power (4). I eventually narrow it down to a Green/Red wire. I test it going IN to the ECM. 0.2v.

This makes no sense to me. Then, for some reason, I look over at my handlebar and realize the kill switch is engaged. I set it to RUN. Test again. This time it jumps to 5v. I retest at the speed sensor, and now it's going 0v to 5v as it should.

Since the bike doesn't shut off when the malfunction occurs, I doubt the kill switch is the problem (perhaps I should open it up for a cleaning...just to be safe).

Still, I want to check what I can see to ensure it's not something damaged in the wiring. If I'm reading the schematic correctly, this power supply wire to the ECM comes from the starter relay switch. It also branches off to the clutch diode (in the fuse block) and the clutch switch. From what I can tell, this is purely a power supply wire set to put out 5v.

Without knowing the inner workings of the ECM, I can't know how or why the kill switch would affect the voltage going to the speed sensor. Does the speedo register speed when the power is off? I just presumed "no" because without power, the instruments have no power, but maybe it's a bit of both?

In all of this, I did disconnect my Power Commander II. I saw no evidence of damaged or compromised wiring involving the unit itself, but best to figure out if I've solved the problem before reconnecting it.

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Well, no luck finding anything wrong. Took apart the kill switch and it's clean. Shot some electrical parts cleaner in to be safe before putting it back together.

5v to the speed sensor only happens when the switch is in RUN.

Everything's back together and the voltages check out at the instrument cluster harness. Next, put the instrument cluster back together.

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If the bike doesnt behave oddly when this occurs, could it just be the cluster circuit? For the effort you've put it, perhaps paying to "borrow" a working cluster, would save some time/money in diagnostics alone. Unless your time is of no value, then piss on it... RIDE FASTER, broken speedo is a mild 'get out of jail free; token. I'll drag out my book today and see if i have any usefull suggestions.

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If the bike doesnt behave oddly when this occurs, could it just be the cluster circuit? For the effort you've put it, perhaps paying to "borrow" a working cluster, would save some time/money in diagnostics alone. Unless your time is of no value, then piss on it... RIDE FASTER, broken speedo is a mild 'get out of jail free; token. I'll drag out my book today and see if i have any usefull suggestions.

I think at this stage I've eliminated everything BUT a busted or failing speedometer. I'll get a wire brush and "polish" the mounting screws for the speedometer before I reinstall it (in case the mild oxidation is causing an issue), but I know there is nothing wrong with the circuit or sensor.

Either here or on another site, I was told crud can get on a hall effect sensor and muck it's ability to read. I don't see how that's an issue, but if the problem persists after this, I suppose I can use a mild gearbox cleaner to flush any crud out with the next oil change...do it on the early side...and see if it never comes back. If it doesn, a replacement speedometer might be the only option. I see no way to "simulate" operation of the speedometer/odometer to see if it does it off the bike. Does anyone make a signal pulse generator for testing these things?

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Well, bike is back together. So far, I've found NOTHING. What I did do is add wires to the speedometer terminals (the pulse from 0v to 5v). These wires run up and over the instrument cluster. Ideally, I wanted to rig up some kind of light that would shine bright enough to show I have a signal. If the speedometer goes out but the light is still working, I then KNOW it's a failed speedometer unit.

Sadly, I can't find shit that works with only 5v max. I'm currently figuring out how to strap a cheap multimeter onto the bike's dash. No luck there, but at least that would do the job.

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Grab a couple of LEDs and a few resistors. Most have a forward voltage of 1.5 - 2.8V depending on type.

Very easy to do.

Maybe where you live. Hardly anyone sells electronic PARTS around here.

I just found a way to hard-wire a multimeter to monitor the circuit (see other thread). If I see no malfunction anytime soon, I'll be looking to fabricate something small and simple to replace it.

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The problem with a light isn't just the voltage but the amperage the light will consume. A small LED might work, might just suck up all the available power.

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If the bike doesnt behave oddly when this occurs, could it just be the cluster circuit? For the effort you've put it, perhaps paying to "borrow" a working cluster, would save some time/money in diagnostics alone. Unless your time is of no value, then piss on it... RIDE FASTER, broken speedo is a mild 'get out of jail free; token. I'll drag out my book today and see if i have any usefull suggestions.

Either here or on another site, I was told crud can get on a hall effect sensor and muck it's ability to read. I don't see how that's an issue, but if the problem persists after this, I suppose I can use a mild gearbox cleaner to flush any crud out with the next oil change...do it on the early side...and see if it never comes back.

Gear box cleaner-WTF?!? Just pull the sensor, look, clean if needed, re-install. No oil flush/cleaner additive is going to remove metal attached to a magnet. Even if it's a one in a million chance you were right there while checking signals, it'd taken a couple minutes and you've spent hours on this thing; why would you pass on checking it?---other than because it's you and you can't accept the possibility that the solution could be simple and undramatic. Best bet would be to just go on ebay and buy one, probably $20-30 and save a bunch of headaches positively knowing that it is or is not the sensor causing it. I'll bet someone here has one they'd sell you or maybe let you borrow to test with.

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I can solder something up for you if you like. I have everything in the basement.

The problem with a light isn't just the voltage but the amperage the light will consume. A small LED might work, might just suck up all the available power.

I picked up a LED flashlight that unscrews near the "bulbs" and runs off 3 AAAs (4.5v). I may test it tonight. The thought that amperage would hamper it working popped into my heat shortly after 10 pm as I was trying to get to sleep. Didn't consider that.

Honestly, if I go a day with the multimeter on the bike and it never malfunctions, a sensitive "test light" would be a better thing to just leave on the bike for the duration rather than what I've set up. I'll let you know. Local "electronics store" could sell me the parts, but I'd have to build it myself.

Gear box cleaner-WTF?!? Just pull the sensor, look, clean if needed, re-install. No oil flush/cleaner additive is going to remove metal attached to a magnet.

Done and done. What I mean by "gear box cleaner" is use something to "flush" to make sure I get as much sediment out of the oil pan as possible at the next drain. I found a wad on the sensor about the side of a drop of water...except black. That might have been the whole deal, or not. Time will tell.

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The flashlight idea SEEMS to work. I tested it last night and it came on and went off when the voltage dropped enough. I'll have to do a better test with the bike running and something wiring it up without my having to hold it, but it looks promising.

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I spun the tach needle off an old Katana once but didn't give a shit because I know what an inline 4 sounds like when it is begging for mercy. Go ride.....................

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