CB1100 Idle speed instability problem

[SportsterDoc]

what i have never been able to work out is how much the difference between the piston and the cyl housing actually is, maybe Dave has an idea, i never asked him back then.

Hi Max. When I inspected my IACV upon removal the piston moved freely within the cylinder housing. If you remember, I even checked the movement of the old IACV versus the new IACV, and I didn't see any difference (checked by plugging it in to the bike normally and turning the ignition key off and on - while watching the piston movement with the IACV removed from the engine). My advice is just replace the IACV. By the way - replacing the IACV completely, 100% cured my idle instability issue, and it has never returned.
[/quote]
Dave, were there any scratches/scoring on the IACV piston, suggesting previous interference from grit or any foreign substance?

[Speed_imp]

The side stand method you posted is right. Also, no one with the problem reported any fault light or codes stored.

How exactly did you connect the probes to the wires? I know, sounds like I don’t have a clue, but if I check mine I want it to be like you did it.

Sorry! I back probed the IACV coils in the ECU connector, today I tried to back probe the IACV connector but almost impossible to fit there a needle. I have my fuel tank out and then I semi install it to get the engine running when needed.

[Lord Popgun]

It all good. I just lifted the tank a little, removed some panels/covers and removed the connector. A small set of needle nose pliers put the needles in very easily. Then I used a DVOM to make sure they had contact (measured from pin to needle) and plugged it back on the IACV. One needle on each coil "hot" lead (sorry, can't remember the colors right now and the book is at home).

Thing I connected a scope probe to each needle. Then connected the probe grounds together and connected them the negative battery terminal as Max suggested. All was well. Nice 12v pulses.

Speed will post up the videos when he gets them. I sent him 2, but one may have gotten lost in the ether. I may have to resend.

[Speed_imp]

It all good. I just lifted the tank a little, removed some panels/covers and removed the connector. A small set of needle nose pliers put the needles in very easily. Then I used a DVOM to make sure they had contact (measured from pin to needle) and plugged it back on the IACV. One needle on each coil "hot" lead (sorry, can't remember the colors right now and the book is at home).

Thing I connected a scope probe to each needle. Then connected the probe grounds together and connected them the negative battery terminal as Max suggested. All was well. Nice 12v pulses.

Speed will post up the videos when he gets them. I sent him 2, but one may have gotten lost in the ether. I may have to resend.

Yes, I received only the 10 seconds video which is very good, nice video of the start up signal. Nice work, I also like the video that Max made (if I am right) with the leds connected. If I connect the probes ythe same way as you did I have the same signal from 0 to 12V, but if I connect the probe to each end of the coil (Bl/Y to Bl/O) I get a signal from -12V to 12V. I am wondering why. By the way, which is the hot lead of the coil? I get 12V pulses coming from both leads of each Coil (Bl/Y to chassis or Bl/O to chassis). Does not matter I disconnect the IACV or not, each lead in reference to chassis ground is getting a 12 V pulse when setting ignition to ON.

[max]

Here's your stepper motor diagram Speed;



See what happens when you connect a 9v battery across the scope probes and then connect it in reverse, the trace reverts to the centerline instead of remaining in the positive section and the scope makes you think there is a 24v signal, which is why Lord popgun asked you:"how exactly have you connected the probe" meaning: pulses with respect to what? ground or the other side of the coil?.

The windings are reversed because if you reverse the magnetic field you also push the rotor and pull with the other coil.

The use of "the force" is then greater which explains perfectly why we have rlets on our bikes

[Lord Popgun]

I can't say for sure, maybe Max or someone can expose on that, Speed. It would be nice to see a detailed schematic of the ECU and all, but that ain't happening. Could just be the ground reference. I can make some good guesses, but without more info it is kind of pointless. I doubt either of the lines is ground, but rather one line is HI the other LOW, maybe from a differential driver, IDK.

The main purpose of this exercise is to see if your results are the same or different tha a bike that is working. So far they are the same. when measured the same.

I just tried to send you the 5min file, but it is 30.9MB and the mail says it is too big. Anybody have any ideas?

Thanks for that Max! Now I know I should have just put the ground leads on the RLETS

[SportsterDoc]

I can't say for sure, maybe Max or someone can expose on that, Speed. It would be nice to see a detailed schematic of the ECU and all, but that ain't happening. Could just be the ground reference. I can make some good guesses, but without more info it is kind of pointless. I doubt either of the lines is ground, but rather one line is HI the other LOW, maybe from a differential driver, IDK.

The main purpose of this exercise is to see if your results are the same or different tha a bike that is working. So far they are the same. when measured the same.

I just tried to send you the 5min file, but it is 30.9MB and the mail says it is too big. Anybody have any ideas?

Thanks for that Max! Now I know I should have just put the ground leads on the RLETS

Do you and speed have DropBox?

[Lord Popgun]

I don’t

[Speed_imp]

Here's your stepper motor diagram Speed;



See what happens when you connect a 9v battery across the scope probes and then connect it in reverse, the trace reverts to the centerline instead of remaining in the positive section and the scope makes you think there is a 24v signal, which is why Lord popgun asked you:"how exactly have you connected the probe" meaning: pulses with respect to what? ground or the other side of the coil?.

The windings are reversed because if you reverse the magnetic field you also push the rotor and pull with the other coil.

The use of "the force" is then greater which explains perfectly why we have rlets on our bikes

Thanks I have been looking for it. So it looks both leads of a same coil are alternatively switching from 12V to ground, it explains why in reference to ground are positive 12V pulses and measuring at the endpoints of each coil (Bl/O to Bl/Y) voltage goes from -12V to 12V which is what the coil is receiving. That is how I measured the signal of the photo



and measuring between Bl/O and Bl/Y where I can find a 105 Ohm resistance



Actually I measured both leads in reference to ground and they both give 12V pulses (alternatively)

I can't say for sure, maybe Max or someone can expose on that, Speed. It would be nice to see a detailed schematic of the ECU and all, but that ain't happening. Could just be the ground reference. I can make some good guesses, but without more info it is kind of pointless. I doubt either of the lines is ground, but rather one line is HI the other LOW, maybe from a differential driver, IDK.

The main purpose of this exercise is to see if your results are the same or different tha a bike that is working. So far they are the same. when measured the same.

I just tried to send you the 5min file, but it is 30.9MB and the mail says it is too big. Anybody have any ideas?

Thanks for that Max! Now I know I should have just put the ground leads on the RLETS

Yes it was the ground reference what was making me crazy, didn't know both leads of a same coil are alternating the 12V output as the rotor of the valve also alternates the poles of the magnets while turning I suppose. You can reduce the size of a video by converting it to MP4 for example in this website: https://www.videosmaller.com

I can't say for sure, maybe Max or someone can expose on that, Speed. It would be nice to see a detailed schematic of the ECU and all, but that ain't happening. Could just be the ground reference. I can make some good guesses, but without more info it is kind of pointless. I doubt either of the lines is ground, but rather one line is HI the other LOW, maybe from a differential driver, IDK.

The main purpose of this exercise is to see if your results are the same or different tha a bike that is working. So far they are the same. when measured the same.

I just tried to send you the 5min file, but it is 30.9MB and the mail says it is too big. Anybody have any ideas?

Thanks for that Max! Now I know I should have just put the ground leads on the RLETS

Do you and speed have DropBox?

Do you and speed have DropBox?
I don't have dropbox neither.

[max]

Thanks Speed, yes this reversal can get you confused so i thought a diagram would help to explain how and why this happens.

Would it be an idea to pm L.P. with your login details for your youtube channel so he can login and post it side by side?