another update: I'm learning (a lot). Vehicle electrics like this are all magic to me.

Using this link: k1100_motronic_2.1_by_Frank_Warner-1.pdf that was provided above in this thread by someone, I went to the motronic connection and did the following:

"1. Measure the resistance from pins 31 to 25, this should be 1k ohms +/- 10% and is the value of the pots resistance.
2. Measure the resistance from 28 to 25, this is the slider to the bottom resistance.
3. Measure the resistance from 28 to 31, this is the slider to the top resistance.
4. The slider resistances should approximately add up to the total measured value of the CO pots resistance. If either or both of the slider resistances are well above or below the CO pots', it is faulty - get a new one."

SO, I did these measurements and got the following:
-Pins 31 to 25 = 724 ohms (total for CO pot)
-Pins 28 to 25 = 1246 ohms (slider to bottom side)
-Pins 28 to 31 = 456 ohms (slider to top side)
1246 + 456 ≠ 724 at all.
-I need a new one.

From what I've learned from this thread, the CO pot can cause unevening running similar to what I'm experiencing with the misfiring. As such, I'll order a new one (probably used on ebay? because I'm a poor college kid) and pop it in, adjust a few things, and see what happens. I'll report back here when I get that done, probably in a week or so. I'd love a confirmation that I have done these procedures correctly and ordering the new CO pot is the correct course of action.

HUGE thanks in advance for all the help on this thread!

(Deleted, double post)

You need a new on OR, you have a poor connection between the pins measured and the pins on the pot???

Woops, sorry for that double post, site was acting strangely for me.

Any way to bypass the wiring and test it straght at the CO pot? While I had it off the bike, disconnected from the harness, it read from 001 to 1019. I set it to 500 ohms as expected and popped it back on the bike and hooked it up. Then I took the readings from the motronic connector.

Watch out for the Frank Warner diagram its easy to get the numbering back to front.

It sounds like you've got the CO pot sorted.

Try starting the bike and see if you've got an improvement.

Yeah I noticed that about that diagram, but I figured it out based on the number of slots in each row on the connector. I had set the CO pot to 500 ohms on each side while it was off the bike and when I put it back on the bike, I got different readings. See my post above. Starting the bike and riding yields the same misfiring. I am confident it has to do with the CO pot now, but I'm not sure whether its the CO pot or the wiring from it to wherever it goes.

The fact that the CO pot was easily set correctly to 500 ohms while off the bike makes me lean towards the wiring.

Agreed

And then there's the question of what wiring to check. According to my Clymer manual, the only other sensor that hooks in with the CO pot. is the coolant temp sensor, and that tested good for me not too long ago.

The coolant temp sensor hooks in to the Br/Y wire coming from the CO pot, then it goes to the motronic connection. The other two wires from the CO pot. go directly to the motronic connection. It should be something in those three wires, right?

I'm thinking of setting up some wires to bypass the harness from the CO pot to the motronic connection to see if I get the same readings.

I may have found the issue with the wiring, although I really have little idea if these tests actually told me anything.

I disconnected the CO pot. and tested the ohms across the connector itself. Here's what I got:

---Ignition ON---
W/B + Br/Y = "-550" ohms
W/B + G/Y = "112" ohms

---Ignition OFF---
W/B + Br/Y = 1002 ohms
W/B + G/Y = 1002 ohms



Due to the W/B + Br/Y ohms with the ignition ON, I figured I'd take a look at the coolant temp sensor as that area is prone to corrosion. Well, it looks pretty clean down there, and the connection is clean, but I also figured I'd take an ohm reading on that as well. I did this by just inserting the DVM wires in to the end of the coolant temp sensor connector. I got the following, with the connector *disconnected* from the coolant temp sensor:

Ignition ON: "-614" ohms // 4.9 volts
Ignition OFF: 001 ohms // 0 volts (obviously)


I know that the coolant temp sensor works using an ohm reading that increases / decreases with temperature, but it seems that the wiring itself should have little to no resistance when disconnected from the sensor. Is this correct?

reconnect the pot and disconnect the sensor. test with the sensor disconnected and also test with the sensor wiring jumpered together.

You may be chasing something here that's normal.

Look around the forum here and get the BMW factory manual, perhaps from the download section or as Crazy Frog if you are permitted to access. Dis-regard the Clymer book

Tested with sensor disconnected and with the sensor connector jumped together. Same results as before on both counts. I'll see if i can get a hold of the manual.

Alright, turns out I've been wrong all along. That Frank Warner diagram pdf says on it to test between pins 31-25, 31-28, and 28-25. That is incorrect. I took another look at his diagram and found that it SHOULD say to test 32-25 for total ohms, 32-28, and 28-25 for each side. I did this on my bike, got a total ohms of 1016, then 516 ohms on one side and 504 ohms on the other.

That said, the CO pot seems to be working correctly. You were right ibj, I was chasing something that wasn't there.

i'm happy you solved it. now is the bike fixed?

Nope, just found that the PDF had instructed the test incorrectly and now I know one more place where the problem isn't. I'm still a little stumped that turning the adjustment screw on the CO pt doesn't change anything while the bike is idling even though I watch the ohms change. I'll pop the new one on when it gets here just for fun.

Tomorrow, I'll be doing the following:
1. Clean injectors
2. Take measurements on the coils
3. Look in to some spark plugs with a stronger spark.

don't change to non standard plugs.....you'll just be creating more problems,
seems like you're just guessing here, now. it's unlikely that it's injectors as they are worse when cold if partially clogged. you could test some coils but that is difficult to pin down unless they downright fail the ohms test. more study is needed before you start throwing parts at it. have you looked at the airflow meter, to see if the air door moves smoothly through it's entire travel + you can ohm that in both directions similar to the co pot

I am almost guessing, as I'm running out of ideas :/. I thought the motronic systems didn't have an airflow meter

You are probably right.......as I have no real knowledge of those systems at all. It would seem to me that there has to be some means of determining the air intake. Perhaps it's all with the TPS that you've already looked at. Or maybe they use a Mass air flow sensor???? Who knows. You'll be the expert when you're finished.
Do you have an O2 sensor in that system????

I think the reason that you can't see any change when trying to adjust the CO pot......is that those changes are just too subtle to feel/see without a CO meter. I expect it's working correctly, now.....it wasn't your problem as it was correct before you screwed it off the end of it's range.

It seems that you had better results by resetting the tps. Has that been re-attempted since the CO pot is back in cycle?

I would like to review the "symptom again, with you.

To me, misfiring means that the engine is physically "dropping cylinders" intermittently like sputtering, stuttering almost staccato like orhit & miss, lurchy jerky, etc.

I'm wondering if you're more likely talking about power surges??? more of a smooth transition where power smoothly but gently goes away & or returns??????

Let's talk about fuel pressure again. Do you have a TEE fitting that you can inset in between the tank outlet and the injector rail inlet and run a fuel pressure gauge with a hose so you can tape it up near the visable area while riding? Perhaps see what the fuel pressure is while the problem is occurring???

Hey ibj, thanks for your patience, means a lot. Your definition of misfiring, dropping cylinder(s), sputtering, lurchy, jerky, is exactly correct for this issue. There is no smoothness about. It's not unrideable, but it's almost no fun to ride.

I have not reset the TPS since I put the CO pot back to correctness. I'll do that asap as well, when I get a chance to work on it some more.

As far as I know, from what I've read on the forum here, there is no mass air flow sensor or O2 sensor. Unlike the older Ks, the airbox is simply an empty box with an air filter in it. The only air related sensor I know of is the air temp sensor in the back of the air box.

I don't have a tee fitting or a fuel pressure gauge, but I was planning on heading to the auto store to get those tomorrow or today. I like this idea.

No airflow meter, that's the old Jetronic system.

If the CO controller is now working and once the engine is properly warmed up, you should be able to adjust it and see/hear a small change in tickover speed as it changes the mixture.

If that doesn't happen then there's a fault in the ECU.

If it does do this the best thing to do is get access to a gas analyser and set the CO properly. Failing that I weaken the mixture until I get maximum tickover speed then enrich it by half a turn. That worked well on my K1100.

Question, are you getting a nice smooth tickover when hot @ 950-1050 rpm?

Possibly a plug-chop at the speed and conditions where you have trouble might help.

I might ask you to Re-check a couple of items.

#1 If you remove the spark plugs, inspect all the porcelain areas very carefully for a small crack.

#2 Insure that all 4 slugs have the little roundish nubby thingy screwed on the top.

#3 understand that the standard plug wires (with the big metal cap) go on the plugs VERY tightly.

#4 put a light coating of silicone grease on the little nubby things, grasp the TAB on the top of the plug wire cap with a large pair of pliers, twist and push hard on the cap till yo feel it definitely "snap" over the little nubby thing as it slides home the final 1/4".

I'm 75% sure you have ignition system issues.

Do the ignition coils have orange colored towers where the spark plug wires attach?

I'll check the plugs soon for cracks in the porcelain.  I basically get 2 hour or less intervals to work on it and put it back together to ride it to my next 'whatever I've got' as a musician.

The coils do have the orange colored towers where the plug wires attach.

All plug cables are seated tightly on both ends, with a definite snap on all of them.

@gerry, I'll try turning it one more time and  listen for idle change, but I've got a good ear for that kind of thing and never heard the idle effected by turning the CO adjuster. Idle misses at a regular interval every half second to second, both while cold and while hot, but stays at 950-1k rpm at all times.

What rpm range does this occur at?

I know I've thrown a lot at you here.......my 100rs seemed to have an intermittent cyl or two now & again while at idle & low rpm...s also the exhaust smells rich & foul when that was occurring. When starting away from a stop, if the cylinder drop out happened to occur when engaging the clutch, it might stall.

Cylinder balance was thought to correct the problem.

Compounding that, I also had bad coils. Even after the coils were fixed, all was not well until a proper balance was finally achieved.

Honestly, it used to only happen in the 1k-3.5k range, but it has been getting worse and doing it at freeway speeds as well now.

And yes, it is terrible letting the clutch out, it sounds awful, not smooth like it used to. It definitely sounds like cylinders drop when the clutch is let in.

I also feel down on power overall, in speed and acceleration. It still pulls like a beast, but nowhere near like it should. There is a hill on the way to my place that I can easily get up to 85-90 mph in that stretch. Today, literally a couple minutes ago, the bike struggled to get up to 70-75 mph on the stretch of hill.

(Side note: took another look at the CO pot adjustment screw. It's working right. I heard the slight change and adjusted accordingly. Took it to max tickover and then richened it a turn. Idle is a bit smoother with much less frequent misfiring. Also, adjusting the TPS back to 0.375v down from my 0.5v setting just made the bike misfire more. I set it back to 0.5v for now.)

Rabidchiwawa007 wrote: Idle misses at a regular interval every half second to second, both while cold and while hot, but stays at 950-1k rpm at all times.

Is there any noise associated with the miss?

I didn't read back up the post to check, but mine had a miss and a tick on every miss.
Coil was arcing onto itself.
The casing had broken at the back of the coil and it was arcing onto the metal brace.
Having said that I did just read you have the orange tops and I think the metal brace is at the front?
Run it in the dark and see if you see any sparks/ arcing.

That's all I got. GL

Could probably pull out the CO section of this post and put in the how to section. Very good info there.

Well, the co adjustment should now be left alone. I think it does not give measurable change at higher RPM.
You are probably looking at ignition.
I'm assuming it drops selective cylinders,..... not all of them at one time, every time? it's not like the whole engine misfires at one time, correct? it's not like you were like turning the kill switch off/on momentarily?

It's more like just some of the cylinders dropping out?

@rossko:  No noise associated with the miss aside from the terrible sound of the engine straining and me going "errghhh, Dammit!" when I let the clutch in.  I've heard about the arcing coil issue, and it can happen on these coils as well as the coils can arc to the engine case just behind them.  I'll be able to put a lot of stuff in the how-to section after I'm done here haha.

@ibjman:  Correct, there is no complete power loss like a loose connection or a bad kill switch/ignition switch.  It's just one or two cylinders (hard to tell) dropping out.  I do not know which ones, if it's all 4 at different times, or just two of them or one of them, etc etc.  Also, don't worry about throwing too much at me, I really love learning about all this stuff, no matter how hectic it may get in my head at times!

when you run it in the dark to look for blue sparks.....jumping, do it with the spark plug tin deco cover off so you can peer in there too. has to be pitch black like in a closed garage. (Watch for exhaust poisoning though)
you can get gassed out in a hurry.
We are sure all the grounds to the coils are correct? might sure running an extra wire from the coil ground to the engine somewhere just during testing.

If nothing is found in the dark test (you can often actually hear a spark jumping).....if nothing is found.......while you have it running, just take the garden hose nozzle & shoot a blast of water all over the coils and in around the spark plug wires & see if it quits running. A completely good system should keep running in a hurricane.

perhaps the dealer would have a way of putting the ign system up on an oscilloscope?

If you can produce it at idle dependably enough.....you can actually, put the plug wires into the coil towers somewhat loosly, so you can get at them easily........while it's misfiring,,,,,,pull a single wire out away from the tower. If the bike quits.......that's probably not the one being effected. Then do it with another one.....one at a time, etc......maybe you could narrow it down to at least which of the 2 coils might be at fault? Some care is needed when doing this as you can get a NASTY shock if you do it wrong. Abruptly removing the plug wire from it's electrical source....will not shock you. as you are moving the part you're holding on to away from the scorce of the shocks.
Experienced mechs do this all the time on cars to see which ones missing? Pull the wires one at a time from the distributer cap to locate which cylinder. If you do it wrong and pull the wire off the plug instead of out of the cap.....you will light up!

I can't remember if you said you had bought one of those infra red non contact thermometers or if it was someone else??????

.....thinking if one is misfiring more that the others (a lot) the exhaust pipe might be substantially cooler than the other 3?

Alright, I'll do those things tomorrow morning. I like the garden hose idea.  Seems legit..  As far as an oscilloscope goes, that would probably be money, and the dealers around here are very non-personable.  They won't really even answer customers questions about bikes.

If I don't see sparks, and then spray with water and hear no change in idle or it doesn't stall, what then?  Isn't it possible for a coil to just fail inside?  These coils probably have 100k miles on them, but I'm not sure if they were replaced at some point.

Was not me that bought the thermometer.  I have indeed experienced the shock of a plug firing.  It gets to your bones.

Its not a good idea to disconect a plug wire while the ignition is firing you just might fry the ignition system.
What's happening here is so similar to my experience that it almost has to be the same fault.
I have a spare ECU and will change it out if it is doing it when back on the road.
It had stopped playing up when it broke the valve and thats the last time I rode it. It's back together and running but I am doing other things before I take it out for a ride.
I went through everything just as Rabid has done and the thing that made it work was changing the setting on the TPS. I still dont know if it was the problem or if it just covered it up by making it run rich overall but time will tell.
I have come to the conclusion that mixture is the problem that makes it miss but as to what exactly is causing the lean mixture has yet to be identified.
Before the Valve broke it was running well but still not really sweet, it would not get to the revlimiter in 5th as it should. It was only a few k short but not right there.

The TPS adjustment I made has really only made it more rideable. The issue is still quite present and is getting progressively worse.

Thats what I feel is that some component is failing slowly because the TPS should not need adjustment if it was set OK to start with and it is good it is only really covering up whatever is wrong. BTW I changed the Ignition amplifier (thing on the battery cradle) and it made no difference. If you have not checked yours then remove it from the alloy cradle and make sure the heatsink paste under it is fresh because if that is old the amp can be overheating.
I would say it isnt the problem but put fresh paste on it to eliminate it from the equasion. You can get heatsink paste from computer shops it is used under the processors to keep them cool.

Will do, Rick, thanks for the idea

My old dad taught me to always do the simple things first. Change the plugs. I know they are reasonably new but they can go quickly sometimes. I have had a set go whilst sitting in my shed with no Ks on them just starting the engine from time to time over a couple of years. Then have the injectors serviced and replace the air cleaner. So that covers spark, fuel and air. Then do the other things if the problem persists. I had a guy come to me once that had a lack of power and turned out he changed to a oiled air filter and a pre filter. He put the pre filter in as he was going outback. I told him to get rid of the pre filter and he rang me and told me I was a magician. Simple things first I say. But good luck. I love this forum for the ideas. I am trouble shooting some things of my own and this forum is great for that.

Gordo.

Rabidchiwawa007 wrote:another update: I'm learning (a lot). Vehicle electrics like this are all magic to me.

Using this link: k1100_motronic_2.1_by_Frank_Warner-1.pdf that was provided above in this thread by someone,

I was but shouldn't have been surprised to read this.

I do know Frank personally, though I haven't seen him for many years. Very switched on with electronics and a nice guy too.

Al

Um, I agree with Rick G - most likely you're using the tps to cover up another problem.

It may be the tps is compensating for an air leak in the vacuum system.

Assuming the problem is an air leak, that might explain why the bike runs better when it is cold. The extra richness supplied by the ecu when cold covers up more of the leak. I suggest you run round the throttle bodies and their connections to the inlet manifolds looking for leaks again. Don't forget the 'O' rings at the bottom of the injectors.

Separately:

The hall effect ignition sensors have been known to go sour when they get hot, just before they fail completely.

It might be an idea to check your fuel pressure.

Best of luck,

Well, I looked for sparks around the coils and spark plugs. Didn't see any. Pulled the bike outside and doused the coils and spark plugs with water while it idling and misfiring. There may have been a SLIGHT change, but not enough to be really obvious. It didn't even come close to stalling at all.

I took the spark plugs out. This how they looked immediately after coming out: https://i.imgur.com/M1tcrkR.jpg
The oil behind the threads on 2 and 4 is kind of suspicious to me. All spark plugs were tight in the engine.

I did a compression test as well; all was normal.
Cyl 1: 120 psi
Cyl 2: 120 psi
Cyl 3: 130 psi
Cyl 4: 130 psi

I'm headed out to get some heatsink paste for the back of the ignition amplifier and maybe a fuel pressure gauge.

I was also thinking (uh oh!) that the spark plug wires probably have 100k miles on them as well. Are these radio suppression wire or regular copper? Either way, it would probably be beneficial to replace them. I tested for spark before putting the spark plugs back in to the engine as well. When I tested each one, I would get a spark at the tip of the plug where it should spark, but also where the bolt (what the socket grabs on to) meets the metal plug wire cap. This happened fairly consistently on all 4. If two of the metal caps are brought maybe a centimeter or so close together, I could see spark jumping between the metal caps. So, as it wouldn't hurt to replace all those wires, I got to looking at these: http://www.euromotoelectrics.com/Ignition-Wire-Set-BMW-K1100-K1-BMW-WSK1100-p/bmw-wsk1100.htm
Are those NGKs a good buy? And is this necessary?

Good photo - those plugs are running seriously weak. Indicates vacuum leak or low fuel pressure.

If you ride it like that you stand a good chance of burning a hole in the top of a piston.

Electrode colour should be light brown.

They aren't the right plugs either - should be single anode. NGK DR7EA is correct one. WRONG, Sorry those are genuine BMW plugs, I don't normally pay for those.

Oil is probably just cam cover weeping, no biggie at the moment.

eek, I'll have to be careful then, as when i bought the bike, the original motor had no compression on the 1st cylinder. (swapped in this motor with 39k on it.)

The plug electrodes looked mostly the color of the metal minus the white build up. But yes, there is some white on there too.

I was almost seriously mad because those plugs were put in there a bmw authorized motorcycle shop.

I'll go pick up some new injector O-rings because I remember one of them had a small tear horizontally in it. I'll also hook up a fuel pressure gauge. Should I hook this up AFTER the fuel pressure regulator?, or right at the tank?, or do one then the other?

One thing at a time.

You need the pressure gauge in the regulated part of the system, so anywhere convenient between the pump and the injectors. On the injector rail would be good.

Good luck,

If you are getting errant arcing from the metal caps then replace them. It will get to the stage that you get a fog and air laden with water and the bike will refuse to start.
I have never liked the metal covers on the plug leads, I have had bad experiences on Hondas with them and we got to the stage that we would recommend to the dealers to remove the metal covers from the plug caps at the 1st service.
The NGK leads that EME are selling will be good gear but Realm engineering in UK are also good
http://www.realmengineering.com/ram%20power%20leads.html
After my experience with Honda and the metal caps I have a very high level of distrust of them.

I hooked the fuel pressure gauge up to the rear of the fuel rail and went for a ride.  At idle, the needle bounces back and forth between around 29 and 36 psi.  When I was cruising at 80 on the freeway, the needle bounced back and forth faster than the eye can see between about 28 psi and 50 psi.  It never seems to stay in one spot.  Here is a video that shows the gauge when ignition is turned on, at idle, and revved up to 5k.  The needle apparently moves at a speed similar to that of my iPhone camera, so it doesn't quite look like its consistently bouncing back and forth really fast, but that's what it does if you were to look at it in person.  Here is the video:

https://youtu.be/1CNjS8-ymBc

When I came back to the bike about 1.5 hours later, the fuel psi had dropped to about 12, from the ~35psi that it shows when the bike is shut off.


@Rick, Sounds like I'll order those NGK plugs. I have two of them on my old BSA and they've been solid. Yeah, I don't like the idea of metal covers for something that should be pretty insulated.

Well, it looks like the pressure comes up quickly to the correct value when the ignition is switched on. Then the pressure drops when the injectors open. I hadn't expected to see such a large pressure drop when the injectors opened. It may be the system isn't delivering the fuel fast enough.

Check for kinks in the fuel line and that its not getting compressed under the tank. Also look at the gauze fuel strainer isn't blocked. I think you replaced the fuel filter so a quick check its in the right way round might be in order. There's a arrow indicating flow direction.

I think you should go ahead and put in the new fpr.

My fuel system loses pressure overnight, its not something which causes me a problem.

Good luck,

Never been inside the fuel tank on a K. Or anything with injection for that matter. I'll find a tutorial or something. Is the rapid movement of the needle on the pressure gauge caused by a faulty FPR?

Also, I forgot to mention that upon deceleration from any speed, throttle closed, the needle stabilized at ~28 psi until the throttle was opened again.

If I put the pressure gauge at the tank rather than the fuel rail, what psi should I expect?

It should be the same pressure anywhere from the top of the pump to the inlet of the FPR.

Yeah, I have just measured the pressure after the outlet of the FPR. Gerry is suggesting components inside the tank causing a slightly lower fuel pressure, so I figure if I hook the pressure gauge in line with the outlet of the tank, it might tell me something. I just need to know what psi the fuel pump is supposed to put out.

The pump will pump up to 65psi and the regulator will get it to a consistent 32-33 psi 2.5 Bar.
Quick test for the pump is to get inside the tank by removing the 4 Xhead screws then undo the fuel line that goes from pump to filter at the filter and with your hand holding the hose inside the tank (if you dont fuel goes everywhere) hold your thumb over the end of the line and press the starter button. The pump will run for 1.5 sec and the pressure should be high enough to push your thumb away and let fuel out then without the thumb over the end point the line into the tank and press the button again and you should get a real good flow not a dribble. It should come out like you would expect water to come out of a household tap with the same size tube attached.
If you get that then the pump is most likely OK. You can hook the pressure gauge up to the tube but it wont show the flow.

Sounds good, I've got some more work to do tomorrow then. Thanks again, guys. I'll have gone through the whole bike before long! I'm going out of town for a couple days starting tomorrow (girlfriends' birthday). I should have new spark plug wires and a new FPR waiting for me when I get back.

What you see when the ignition is on but the engine is not running is correct (36 psi).

Needle vibration is caused by pressure drop when the injectors open.

This may be a result of fuel supply constriction not allowing fuel flow to keep up with demand. Could be caused by any of the problems listed in my last post plus blocked fuel filter if you haven't changed it. Very important to install it the right way round.

Injectors are turned off during deceleration hence no needle vibration. 28 psi is too low, should stay at 36 psi (I don't think the pump is off).

Best,

ps. Be careful of the pipe to the fuel pressure gauge, you've fuel at 36 psi in there, if it comes off at speed you've got a serious fire hazard.