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Discussion Starter #1
Any way to test an ECU (1.6M) without swapping with another? I'm still chasing gremlins and want to be able to rule it out... Don't have a spare handy, nor do I want to spend money on one if isn't the problem.

I did have it connected to a Techlogic VDST system recently... Appeared to be working fine aside from "expected" error codes.
 

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Discussion Starter #3
Hmm... Interesting idea. But really I can do that with the ECU in the bike - remove the plug cover and tada, you can run a probe to the wiring and test whatever you like while the ignition is on. That's how I verified the TPS function. You just need a schematic to determine what voltages are "normal" and which pins are connected to each widget.

It seems that everything is ok when you test. Voltages at the various sensors are as they should be. Everything reads correctly. The sensors are either new, or have the correct resistance (ditto the coils and injectors). The ECU was throwing a code for the crank position sensor when we checked it, we replaced the CPS (with a spare used one, so it's not 100% that it is good) and the code cleared fine while we had it connected. 150 miles later and the problem came back.

My next step is to install a brand new CPS (arriving soon). If that doesn't fix it I'm going to assume it's the ECU. It's the only thing left that makes sense. I've checked just about everything else.
 

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I've yet to dig deep into one of these bikes. Are the cps wires shielded? If so, I'm thinking exposed shielding ,ground loop, n noise... maybe?

Is finding a proper running bike to put your ecu into out of the question?
 

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Old Wizard
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The CP sensor is just a pick-up that sends a pulse signal to the ECU when a magnet embedded in the flywheel passes near its internal coil. It's shimmed out to a specified clearance from the flywheel.

If the gap is too big, or fluctuates due to a loose flywheel or cracked engine casing, the rpm signal will be erratic.This will result in running issues, such as a 6-7K rpm brief cut-out condition like hitting the rev limiter. If you check the tachometer while it’s happening, if it's the sensor, or ECU-to-sensor wiring, the rpm reading will drop to zero.
 

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Discussion Starter #6
Bingo - the tach doesn't drop when it loses power. It will get "notchy" if you try to free rev it (it steps noticeably).

So what the hell am I dealing with, if not the CPS or the ECU?
 

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Old Wizard
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I seem to recall a case where an owner said that replacing their tach solved a similar problem. I don't understand why it would, but I suppose you could disconnect it and see what happens. Another possibility is that you have a vibration-sensitive component in the ECU. Ask your dealer or a friendly owner if they'll lend you one for troubleshooting the problem.
 

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Discussion Starter #8
Hmm. Problem is I don't know anyone who could lend me an ECU to test. And I don't want to spend 200 odd bucks to follow a hunch until I exhaust all my other options. Crappy position to be in.

It's also intermittent. I can ride for 50-60 miles without anything going wrong, then BAM it will be nearly unrideable without warning. So "testing" it is time consuming and risky, I'm worried about getting stranded (or worse, running the motor dangerously lean while I nurse it home).

I'll try the tach idea though... easy enough to test.

I should note - replacing the CPS made it happen much less. Before it would conk out as soon as it hit operating temp, within a few blocks of home. Now it can go for quite a while before it pops up. Which is why I think the CPS is the issue, or at least related.
 

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Discussion Starter #9
I should note that I'm getting a new CPS this week. I will try it with that. If it persists, I'm buying a replacement ECU.
 

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Long shot, but free and easy to do, disconnect charging and have a go.
If it helps put a capacitor(eng?) inbetween.
If current peaks reach the ecu it will go into a limp mode, to preserve it.
Proper fix then is to replace the rectifier, much better options than stock are available.
 

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Discussion Starter #13
IIRC the code on the ECU was CPS open circuit. It was a current code (as opposed to the filed codes that were due to me messing around with the other EFI sensors). Once we swapped the CPS and reset the ECU it stopped throwing the code. 150 miles later I was back to square one.
 

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Discussion Starter #14
Long shot, but free and easy to do, disconnect charging and have a go.
If it helps put a capacitor(eng?) inbetween.
If current peaks reach the ecu it will go into a limp mode, to preserve it.
Proper fix then is to replace the rectifier, much better options than stock are available.
I'll give it a try next time it happens. My rect is functioning fine and never exceeds 14 ish volts on my dash voltmeter. Doesn't mean there aren't any quick spikes though.
 

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JEC, have you preformed the "wiggle" test on the wiring harness.
Something else to look at is the cps connector plug. Check the wires on both sides of the plug. Thinking that you changed the cps already and it worked for a bit then quit again leads me to believe that is could be a loose connection.
Take a good look at the pins on the harness side of the cps connector. There may be one that is not completely inserted ( backed out a touch)

Intermittent wiring problems suck! I know from years of working on Italian cars with "Factory Homemade" wiring harnesses.
Thanks for bringing back nightmares:eek:
 

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Discussion Starter #16
Yeah I've been doing wiggle tests all over the harness to try and find the issue. The connector seems fine, I always had it zip-tied together for security and sealed with dielectric grease (I'm obsessive with electrical details after having worked on old British bikes).

It's also not enough to kill the bike completely, it just runs REALLY badly. Backfiring violently through the intake, afterfiring in the exhaust, lose about 2/3rds of the power. Stuttering and sputtering at steady throttle and on accel. We suspected the TPS originally but it gives perfect readings according to the VDST and my voltmeter tests.
 

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Discussion Starter #17
Update

Been going over the wiring and discovered a hack job connecting the regulator... Like three-splices-in-one-length-of-wire-wrapped-in-electrical-tape hack job. The whole thing is butchered like this, every wire going to the reg is poorly done. No obvious signs of overheating or shorting out, but it still needs to be addressed. I'm going to ditch all of it and install a Mosfet with hard wires to the battery and stator.

Charging issues would make sense... However my voltage output has been right in spec so I don't have any apparent issues outside of the ugly wiring job. Unless it is shorting out or creating intermittent spikes.
 

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Yeah I've been doing wiggle tests all over the harness to try and find the issue. The connector seems fine, I always had it zip-tied together for security and sealed with dielectric grease (I'm obsessive with electrical details after having worked on old British bikes).

It's also not enough to kill the bike completely, it just runs REALLY badly. Backfiring violently through the intake, afterfiring in the exhaust, lose about 2/3rds of the power. Stuttering and sputtering at steady throttle and on accel. We suspected the TPS originally but it gives perfect readings according to the VDST and my voltmeter tests.


That's exactly what my bike did when the fuel pump relay started to fail.

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What about the yellow ignition relay?

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