Took the bike out for a ride today and had the most disheartening experience.  Apologies in advance for the long write-up....

I started it up and it seemed to be running fine.  As I was backing up out of the garage I turned the bars to lock and the engine died.  Restarted and everything was fine, but thinking that maybe I had a short somewhere I moved the bars about and jiggled the wires running from the bars to under the tank.  I reproduced the issue by moving the bars to lock.  I recently added an alternator exciter light (I have installed an Acewell speedo).  I wasn't having problems with charging, but I saw a thread on the forum about the lack of an exciter light resulting in a an alternator charging failure and I thought I might add one just to be safe.  So, I figured that maybe what I did with the exciter light was causing a short somewhere.  Or maybe the light was't appropriate.  I used an LED that was 1/4 watt with a 680 ohm resistor built in to it (purchased from radio shack for something else...had it lying around and doing the math, I thought it would emulate the 3W incandescent... but maybe I was wrong on that).  So, I pulled the tank, unplugged the exciter light, reinstalled the tank and starter her up.  Everything was running fine and I did not have the problem with the engine dying no matter where I turned the bars.  Problem solved, I thought.  I rode off a few miles on an errand and parked the bike.

A few hours later I started up the bike, no issues.  Rode about a half mile and all of the sudden had a massive lack of power, followed by many back fires.  The bike died.  I restarted it, just barely, and was able to ride a little with lots of backfiring and lurching.  Very little power, and to get even a little power, I had to keep the throttle at least half way open.

It sounded like one of the cylinders wasn't firing.  On a lark I wiggled the injector wires and cylinder 2 wire came off in my hand.  Upon close inspection I saw that I had installed the retainer clip backwards (I had the injectors out months ago chasing down another problem, which I solved) and therefore it wasn't securely attached to the injector.  I reinstalled it properly, the bike started and I was able to limp home, but the bike was still not running well.  It would barely idle and I had to keep a bit of throttle on to prevent a stall when idling.  It seemed as though I wasn't firing on all cylinders.

So I pulled the plugs to see how they looked.  Cylinders 2 and 3 were perfect.  Nice grey tips on the plugs and looking into the cylinders, they were dry.  Cylinders 1 and 4 were slightly fouled, smelled slightly of gas when I pulled them, and looked a little wet inside the cylinders.  

I dawned on me that the commonality is that 1-4 runs on one coil and 2-3 runs on the other coil.  So, I thought maybe I had a bad coil.  Looking at Crazy Frog's trouble shooting guide, I tested the coil resistance.  On the 1-4 coil the primary was 1.0 to 1.2 ohms; Crazy Frog's guide says it should be 2.6 ohms.  The 2-3 coil tested at 2.6 ohms on the primary. I couldn't get a reading off the high voltage terminals on either coil.  I must not have been probing them properly.  I removed the plug wires at the coil terminals and put my probes in to contact the metal inside...not sure what I was doing wrong. (I understand from Crazy Frog's guide that they should be 12.6 ohms). If anyone can tell me how to properly probe/measure the high voltage portion of the coil, I'd appreciate it, as I think it would be helpful in confirming (or refuting) my diagnosis.

Based on the low reading on the primary, I'm thinking that I've got a bad 1-4 coil and that I need to replace it.  Based on the above, does anyone agree/disagree?

However (and this is the reason for the long post) are any of the other things that I described above related to the coil (apparently) going bad?  Is there any chance that my exciter light did something to the electrical system causing the coil to fail?  Is there any chance the #2 injector coming unplugged somehow lead to the 1-4 coil failure?  Or maybe I just had a bizarre confluence of the coil failing unrelated to anything else?

Measure between the towers where the plug wires go, down inside where the copper contact is, should be around 10000 ohms.
The backfiring sounds like dirty ignition switch, there has been a few threads recently so have a search from the forum page and several recent threads will turn up. Turning the steering may have been pulling slightly on the cable from the ign switch.
The exciter light needs to be 3 watts as that will get it going low down the revs. You were fotunate the alternator was working at all.

I've moved my ignition switch from the bars to mounting point I fabricated under the tank.  And I had it apart a few weeks ago to clean it.  So I'm pretty confident that this is not the problem.  

I do intend to get back to the exciter light when I get a chance.  I read elsewhere on the forum that sometimes the alternator will work just fine without the exciter light if there's some residual charge/magnetism present.  I only have a couple hundred miles on the bike without the exciter light, but haven't had a charging problem yet.  However, I do plan to get back to the exciter light (which, by the way, when I had it hooked up seemed to function like the stock...it would go on when the ignition was turned on, stay on when the bike was fired up and the go out after blipping the throttle).

I probed the coil towers as you described.  I was quite sure I was contacting the copper contacts with my probes.  I'll give it another try since I obviously am doing something wrong.  

In the interim, any opinion on my bad coil theory, especially given the low resistance measured on the primary of the 1-4 coil?

Additional update: I confirmed that I have no spark in cylinders 1 and 4. But I was still unable to measure resistance on the main part of the coils, even making sure that I was touching the copper contacts inside there.  

Really thinking I have a bad 1-4 coil.  Would really like to see if anyone shares that opinion before I go tracking down the part.

Also, assuming it is a bad coil, can I fit a newer model coil from a 4 valve 100 or an 1100?  The part numbers are different on Real OEM, but I thought I read somewhere that they are interchangeable.

Edit: 

Should have consulted the forum first.  My last question is answered by this thread: https://www.k100-forum.com/t6114-1984-85-k100-ignition-coils

Looks like I have the bad old all-black coils and need to upgrade to the red-topped ones.  (And K1100 coils won't work, at least not without other part swaps and then its still probably its problematic).

you may have to lookup how to test the hall effects ...and maybe more important the wiring that feeds them etc

test the connections under the tank for the connection to the hall effects ...is it corroded at all

I say this as its the last thing to look at ....before you look at the ignition unit....if the primary of the coils tests positive ....of corse it could be dud connections to the coils from the ignition computer ...somewhere along that path... fingers crossed

If you aren't getting any reading when you put the meter across the towers then that means the secondary coil is open circuit. It will usually keep going because the voltage is high enough to arc across the gap but it will get to the point where heat and the arcing detroy it and it no longer works at all. If you do need one get a new one they are pricey but buying a used coil is a chance, it could easily go down the same path in 6 months time.
Just looking at the model and an 85 would have the old grey coils which is amazing as it has lasted this long.

Thanks guys. I will check the HES just to be sure as per Charlie's advice. I cleaned all connections under the tank a few months ago with deoxit. So I don't think a corroded HES connector is the problem. But the HES could be a problem...I've never checked them. There's another thread started that raises some questions about hoe to do that test. I had some of the same questions myself so I'll watch there for answers before proceeding.

One question for Charlie: would the HES or other wiring issues explain the problematic resistance readings I'm seein at the coils? Is think not, but I'd rather ask the question than misunderstand.

From Rick's post it sounds like I ought to get new coils no matter what.

When I bought my 1985 K100RS I replaced the original coils with the newer models as a matter of course, even though they were funtional. If you wish, I'll send you one.  For the price of the postage, it could sort your problem, if only a temporarily.

Brickrider, that would be excellent! Thank you so much! I'll send you a PM with my info in a little while (stuck at the doctors office using my phone, can't seem to use the PM function without being on a regular computer).

Brickrider, I just sent a PM.  Please let me know if it does not arrive (I couldn't see any confirmation via the PM system, but I'm pretty sure it went).  Thanks again!

i thought that you said that you had tested the secondarys of the coils   ?  about 10k to 12 k ?

primarys should be low ohms

so was then suggesting the next steps

looking back I see now. you have an open 1-4 coil ...which could manifest itself in all sorts of ignition issues

apologies


I see a test coil is on its way ?  great work guys

Charlie, thanks, and no worries. I now undersand what you were saying. I need all the help I can get!  If the coil swap doesn't help, then I'll look at the HES next.  Still waiting to hear from Brickrider on arrangements to get me the coil; I'm guessing he's busy working (or, better yet, maybe out riding!) today. Members of this forum are great.  I'm sure I'll hear from him soon.

To clarify, I'm getting no resistance whatsoever on the secondarys of either coil.  If I undersand Rick's post correctly, this is a sign of a failure waiting to happen.  Or, more accurately, the failure has occurred but it still working (at least on my 2-3 coil) due to a benevelont malfunction.   However on the 1-4 coil I clearly have much lower resistance on the primary than I should have (about 1.0 ohm) whereas on the 2-3 coil I have the proper resistance on the primary of about 2.6 (though one time it measured 2.4).

As noted above, I've got the old black (grey) coils that I have now learned are prone to failure.  I think it all adds up to one bad coil and the other probably not likely to last too much longer. 

I'm curious, would there be any harm in swapping my coils around to see if I get good ignition in cylinders 1-4 by using the 2-3 coil (which is known to be good (enough))?  If there's no danger in that, and it resulted in combustion in 1-4, then I'd at least have a solid diagnosis.  Thoughts?

That would be a very definitive test to isolate the problem part.

i wouldn't do it ....
the low resistance on coil 1-4  is dangerously low for the ignition computer

I wouldn't trust it to not affect the other side of the ignition switching devices (2-3)

but you could try coil 2-3 on the 1-4 outputs .

wait till you have another I recon

Just a word of caution you will see quite a few K1100 coils on fleabay that say K100, K1100. They are NOT the same. If you come across some K100 coils that are a dark brown with orange towers and the seller will refund if they are not OK go for it as they are later model K100 and much better.

Rick, I gather these are the correct coils, right?:

http://www.ebay.com/itm/Ignition-Coil-BMW-K100-early-12-13-1-459-513-Bosch-BoignCoil-K513-x-2-/252033953221?hash=item3aae64edc5:g:1aQAAOSweW5VU2vF&vxp=mtr#shpCntId

That price: OUCH!

I haven't seen any used ones like this, but I'm going to browse around a bit more.  I've found a few of the old style like I presently have for a lot less...but it sounds like the chances of the old style failing are high.

Yes they are the correct K100 coils. The old grey ones do fail easily and often. It has taken 6 years to get a pair of the old grey coils to use on an 83 K100 that I will one day build. The things will probably drop the bundle as soon as I use them.

Be quick they have only 1 day to go http://www.ebay.com/itm/BMW-k100-k1100-Bosch-Ignition-Coils-NEW-/191835348907?hash=item2caa471fab:g:W5sAAOSwX~dWiqOT&vxp=mtr
See what I mean they are K100 and not K1100

I need an address if I'm to send one of the 1985 K100RS coils.  I haven't heard from you yet....

Brickrider, I tried the forum PM function, but it didn't work. I'll try again in a moment. But if that doesn't come through, Could you email me at justin@reynoldslaw.us, and I'll get get you the rest of my contact info and we can discuss additional details (at a minimum, I want to cover your postage). Thanks!

Edit/follow-up.  Sent the rest of my info (again) via forum PM.  If it doesn't arrive, please email me per above.

Rick, that's a great find!  Just made the purchase.

Ok, bad news. Got the coils from Brickrider (thank you!) but the problem remains. No spark or firing in 1-4. To confirm this I pulled the 4 plug and tried to start the bike with the plug out to be sure there was no spark. Confirmed. Turned off the bike.

I then tried again to start the bike again. At first I hit the starter button and got nothing (I don't think the fuel pump ran, but not sure). Then I hit the starter button again and all hell broke loose. The bike didn't start but the starter motor started and wouldn't stop. The kill switch didn't turn it off, nor did the key. I only got it to stop by disconnecting the battery. Unfortunately I was not quick in doing this and my battery is almost flat now. It's on the charger

I know from other reading that this series of events means that I may have welded the contacts in the starter relay. I also know a main cause of this is a weak battery. I don't think my battery was weak, but it's possible. Are there any other causes I should be investigating?

I've got the starter relay out of the bike but can't seem to figure out how to open it to see if it's welded. Any tips on this?

I'm also going to have lots I other questions as I troubleshoot through this. But for now, I'll pose the general question of whether there's anything else I should be checking at this stage?

Just checked the starter relay using the info here. https://www.k100-forum.com/t10153-starter-motor-wont-stop Amazingly, it seems that my starter relay is not welded. I got 0v on the small pins/wires with the starter not cranking. It did only show 4.4v with he starter cranking (I thought this should show 12v...is that an indication of a problem?). Had infinite resistance (open) across the large connectors, which was correct per the above thread.

Also, with the tank off and the battery reading 13.1v after charging I hit the starter button to see what would happen (also necessary for the test above) After letting the button go, the starter motor stopped cranking and I heard the relay click about a second later. I think that means my relay is ok as it would mean the contact is opening. Can someone please confirm?

Assuming my starter relay truly is ok, what do I look at next? Do I just chalk up the starter to a low battery that I didn't realize, or should I check something else?

And of course I still have the 1-4 non firing problem.

One other thing. Please see this thread. https://www.k100-forum.com/t10150-wiring-in-non-bmw-handlebar-switches It describes a problem I was having when rewiring my starter switch and how I jumped my headlight to my main switched power at the right hand plug. The result if this is that my headlight stays on while starting, rather than going out. I'm grasping at straws, but could that be messing with my starting and the load shed relay?

all may not be lost on the coils ....
they are a wasted spark system ...that is it fires both plugs (1-4) at the same time regardless ...except if you have one plug not contacting earth at all . you need to tie each of the plug outers to earth ....perhaps just a coathanger wrapped around the plug and connected to earth ?
in any case attempting to test the issue without proven good plugs is a lost cause .


I didnt like the sound of 1 ohm resistance across the 1 4 coil primary ....just saying

good luck with the start relay ...perhaps you can refinish the contacts ...after you have got them apart ....its scarey stuff when that happens eh ?!!

Thanks Charlie. Yes, very scary when the starter won't stop! I never got the relay box open. But will be sure the contacts outside are clean befor putting it all back together.

I have the "known good" coils from brickrider on the bike now. Tested them before installing and the primary resistance was where it should be. 2.4 ohms.

I'm confused about earthing the plugs as you describe. Where do I attach the coat hanger? Onto the metal of the plug itself? Or the outside plug holder, which is also metal. Apologies for being dense. Also how are these normally earthed? The coils share a brown earth wit going to both. I'll clean those contacts for good measure.

Also the plugs are all new. Only a few hundred miles on them. They are about 2 yrs old though. Thinking that the plugs themselves probably aren't a problem, but will swap them around with the other 2 that are working to check. More to come tomorrow!

coathanger wire around the threads that normally go into the head   you still need to insulate the spark plug wires from earth

and then the other end to a bolt or something  perhaps cam cover bolt or fuel rail bolt ...but not insulated from the head so under the bolt head just lightly done up but still applying pressure to the rubbers to seal in the oil

the idea is that the spark can jump from earth to the centre electrode on both ends of the one coil

something like this



hope you measured the secondarys of the coils ....somewhere between 10,000 to 12,000 ohms ? terminal to terminal ?

OK, will try that this evening.  

I did measure the secondary resistance on both of my "new" coils.  They showed no resistance/totally open.  I know that's not good, but chalked it up to not knowing how to measure properly (though it does seem easy to touch the copper contacts inside the towers, which is what I did).  And since Brickrider told me they worked in his bike when they were removed, I assumed that they were good.  But now I wonder if maybe my "new" 1-4 coil is suffering from the same problem as my old.  I have a new red tower version coming in the mail today.  I'll try that in place of the 1-4 that is not working as well.

Still no success, but tried a few things and am at a dead end.

I took out all the plugs and tested them for continuity. One was giving me some weird readings, resistance jumping up and down while the other 3 were reading as having continuity and tiny resistance (.01 ohm). So to check things out, I swapped 1-4 for 2-3. 2-3 still fired and I still had no spark in 1-4. So, I've ruled out the plugs.

I got my new, red tower coil today. Resistance in the primary and secondary measured as it should. Installed that on the 1-4 cylindars and still no spark there. So, I think I've ruled out the coil as the problem.

While the bike was running (on 2-3 only). I tested the 12v + and - feeding the 1-4 coil. That showed only about 9.5 volts. Don't know if that's right or not. Unfortunately the bike stalled before I could check the same 12v + and - on the operational coil. When it stalled I gad zero power. It appears that my battery wasn't charging and that it ran down. I don't know if the low 9.5 reading I found above is due to the fact that the battery was dying during the reading process.

Unfortunately my battery is dead and I didn't have a chance to try Charlie's coat hanger earth test above. I'll need to get a charged battery back in place before I can try that test.

One other thing. I have a lithium iron battery (Scorpion brand). Haven't had trouble with it before but I cave run it down a few times. Don't know if this might be any part of the problem. I'm charging up my old lead acid battery to put back in just in case.

Any advice on what to try next?

The lithium battery should be able to take going dead flat quite a few times, they are in that regard far more hardy than a wet cell lead acid.
you wont get any neg at the - terminal of the coil unless the engine is running or at least turning over on the starter but you should get 12v pos at the + side of the coil whih the key and kill switch on.
You are right about wiating till you have a well charged battery.
Disconnect the wire from the pos of the coil and see if the voltage varies, it should go up to 12.6v.

The saga continues. Seems my lithium battery is totally dead. Won't take any charge at all. I had my lead acid battery sitting around. Charged that for 24 hours. Was showing 12.7 volts so I put it in. When I touched the contact the bike started firing, classic sign of a stuck/welded starter relay. Wonder if the starter was cranking due to a stuck really and I didn't realize it and that fried my battery? Pulled everything apart, gave the starter relay a whack. This was sufficient to disengage the starter relay because when I rehooked the battery the bike didn't crank.

Turned the key on and measured the + power wire at the coil. My battery isn't strong so that was showing 11.7v and my battery with the headlight on was showing 12.2 or 12.3v.

I didn't want to try to start again given the precarious state of my starter relay and questionable battery. Looks like I'll have to buy a new battery before further testing. I probably also should get a new starter relay, just to be safe since my current one seems questionable.

Hoping a recap of what (I think) I know will help someone give me next trouble shooting steps.

1. I'm getting power to the coils (there's apparently a voltage drop. Not sure if that's a problem or a sign of my weak battery....advice?)
2. I've got good coils. Known good pair from a forum member and also swapped in a red tower newer coil on the 1-4 non firing cylendars with no success.
3. Spark plugs are good. Determined that by swapping them around.

Still need to do:

1. Charlie's earth test (with coat hangar, per above). Need to wait until I've got a good battery to do that though.
2. Check HES. Again, need to wait until getting a good battery.
3. Check 12v- wire while running or cranking the starter. Also need to get a new battery to do this.

One thing I tried was to test my spark plug leads for continuity/resistance. I couldn't get a reading on either 1 or 4. Tried probing the plug side with a paper clip attached to my multimeter touching the copper inside. And in the coil side just attached to the obvious copper part. Advice on what I'm doing wrong or how to test this properly.

Is their anything else I should try?

KJustin wrote:
One thing I tried was to test my spark plug leads for continuity/resistance. I couldn't get a reading on either 1 or 4. Tried probing the plug side with a paper clip attached to my multimeter touching the copper inside. And in the coil side just attached to the obvious copper part. Advice on what I'm doing wrong or how to test this properly.

Is their anything else I should try?  

that's the right test , but you may need to set your multi meter to the 10,000  ohm scale to see any thing

possibly even to 200,000  ....if its an non auto ranging meter, shouldn't have that issue with an auto ranging one ...except to keep it still whist making contact at both ends

but not looking good so far , perhaps the cheapest way to rectify this might be to get the elcheapo  plug leads from almost any of the car shops   the number 4 would be about 13 inches long ...whilst the number 1 would be about 15 inches long ....they should measure about 2.5k for the short one ...maybe 2.5k - 5,000 on the longer one ...   think I got a pic ...but its at home ...so cant post till tomorrow
good luck with the relay

one of our local guys got an 80amp relay out here far cheaper than the automotive types ...  or even the bmw accessories places ....seems to work for him quite well

Would appreciate the picture when you get a chance. Thanks. I'll give it another try to test the spark plug wires again tomorrow with the guidance above.

In terms of trying some cheapo plug wires, will any do? Or do I need to be sure they have to have a resistor built in?

On the relay, probably will buy a replacement I found on line for about $50 USD. Still a steep price (but better than own at $100+) but it Looks like a direct swap, and I'm willing to spend a few extra bucks for ease and certainty.

This is what you need
http://www.ebay.com/itm/Starter-Relay-Solenoid-Motorcycle-For-Suzuki-GSX-R600-2001-2003-GSX-R750-00-2003-/351701394410?hash=item51e30963ea:g:KosAAOSw8RJXBcre&vxp=mtr

What Rick says. You'll need to make a bracket to mount it but it will fit inside the relay box below where the existing starter relay is. you can connect the wires either way round - that goes for both the heavy battery cables and also the wiring loom wires.

Alright, you've convinced me to try this relay. Will place an order soon. Either of you happen to have a picture of a mounting bracket handy?  If not, no worries. I'll figure something out.

No time today or for a few days to work on my other problem. Will get back to it soon and will likely be bugging you good folks for more advice when I do.

 IMPORTANT EDIT: This relay appears to be incompatible with the ICU and may cause damage to the ICU. See this thread for details and a possible solution to the issue:  https://www.k100-forum.com/t11140-starter-relay-i-think-problem.  To be clear I'm providing this info not to complain about the advice to try this relay (I take full responsibility for what I do to my bike and have no ill will toward those who made the suggestion), but rather to be sure the info on the forum is as complete and accurate as possible.

A piece of 1.6mm steel sheet made into a U shape and pop rivetes to the side of the relay box or fastened to the original mount for the relay. There are 2 slots in the rubber mounting.

sorry for delay
try these leads   ....the silicon type   for the cheapies  ...just take your multimeter along and confirm they have some resistance end to end

this might help sort the issues without a great deal of expense ...well for testing at least

make sure that the coil end contacts the copper inside the coil tower
so with the leads fitted you should get a high reading ....erm up near 20,000 ohms end to end ?



hope that helps

Charlie, many thanks.  That clears things up (not that YOU were unclear before; I'm just weak on a lot of this stuff).  Also looked around on line and it appears that most plug leads have some resistance; will take the multimeter to the parts store and run some checks before buying.  And, if this solves the problem, will purchase K-specific leads for the permanent fix.  

Going to be several days till I get back to working on this. Dealing with a busy time at work and personal life, including trying to help a close friend who is very ill with cancer.  Sorry to bring the forum down with such details....

Will be back with a report when I have the chance. Best, Justin.

be well ...hope it works out ok

cheers

Was able to steal away from everything for a few moments this evening. Used the opportunity to test my HES. I used Crazy Frogs guide, but not sure I'm doing it right.

First I removed the HES plate from the bike. Just left it hanging. Then I hooked up everything exactly as shown in CF's guide. I'm using the famous radio shack LED light 276-270 (which has the built-in 680 ohm resistor). Got no light on testing pins 2 or 5. I read on the motobrick forum that CF's guide has + and - backwards. So I switched them, putting + to pin 4 and - to pin 3. Tested 2 and 5, still no light on either.

On a lark, I put the - running from the LED on pin 3, the + from the battery on pin 4 and then touched pins 2 and 5 with the -from the battery. That gave me a lighted LED on both pins. But when I put a feeler in the HES gap the light stayed on, for both pins.

I'm confused. I would have thought that, if my HES was bad, since I have no spark on cylinders 1-4, I would have found that one of the two sensors was bad and the other good. But in all configurations I seem to be seeing both sensors are bad. Or am I misreading things?

Could someone please set me straight, including any tips on the proper testing method?

And now I've put the HES back in and I can't even start the bike to run on cylinders 2-3, which I could before. Presumably this means my HES us totally shot, or I killed it during testing, or I reinstalled it wrong. I did mark the position with a sharpie marker befor removing it. So that should be correct. But how sensitive are they to set?

So frustrating. All advice welcome. Thanks!

I wanted to report that I have solved the problem.  It turns out that it was a bad Hall Effect Sensor (for future readers, there's a separate thread on this that is worth reading if you think this may be an issue...that thread also contains a cautionary tale of what not to do when testing).  Put a new set of HES in tonight and the bike fired right up! Actually, I probably also had a bad or soon to be bad coil as one of them was clearly not testing properly.

Thanks to all who assisted me with this.  Really appreciate all the help!  Best, Justin.

good to hear  thanks for reporting

that's very good news, Justin!  I hope you can now get out and ride it rather than wrench on it!

On the road again...

Excellent news and thanks for posting the solution.

Good write up.  I came on the forum looking for a similar solution.  Mine has the low power problem, but only when it gets rained on.  I'll have to check the hall effect sensor, and connections.

Hi reidman. Would be better if you started your own thread on that issue otherwise  information gets mixed up, hard to sort and find when searching. This one's been marked as SOLVED anyway.
Cheers