I recently removed the frame of my K1100lt for powder coating, leaving the wiring loom intact apart from unplugging the ignition switch, left and right handlebar switchgear etc. After removing the powder coating from the  frame earthing point (that is under the fuel tank if it were on the bike), and also at the point where the frame bolts up to the gearbox (on the right, near the near the battery). re connected the multiplugs, clutch switch etc. Problem now is that the brake lights were not working, running a ignition switched live to one of the green and black wires solved the issue. All else works except the starter button does not operate the starter. Checking the two wires that power the starter relay / solenoid, if tested with a multimeter, both show 12.54 volts, if the same wires are tested with a 12v test light, the light is very dim at both wires (black&yellow wire and brown&blue wire) also, after testing them with the testlight, the clocks remain lit up (as if the ignition were on pos2 ) even when the ignition is turned off and the key removed, they do, however, turn off again if i switch the ignition on and off again (without the test light being connected).  I have unplugged and cleaned each individual multi plug and connection, cleaned all of the earths, bypassed the clutch switch and checked the side stand switch, i am still getting the same results. any input will be much appreciated.

































 I have unplugged and cleaned each individual multi plug and connection, cleaned all of the earths, bypassed the clutch switch and checked the side stand switch

Hi mate you don't say if the bike was running prior to strip down, assuming it was, the starter motor plays a major part within the electric system on the Ks.I would double check all connections to the starter. Have you looked on the FORUM section as well. Hope its a case of woods and trees 

The starter relay receives its 12v via the start button. However, it receives its 0v (brown & blue wire) from the ECU - this allows the ECU to override/disable the starter.
If both wires to the starter relay are showing 12v (I assume this is when you are trying to start it), I would double check all the connections to the ECU to start with.

Make sure that you've removed powder coating from the engine mount bolt holes so that electrical contact is made through the engine and gearbox. Also, do you have a ground wire on the handlebars coming from the righthand switch cluster?

You might want to chase the threads for the starter mounting screws into the transmission with a tap to improve the grounding through the starter.  

You might also want to make a cable up with 14AWG stranded wire and ring terminals to connect the frame ground under the tank to the engine ground on the side of the transmission.  This will make a more direct ground path from the under tank ground back to the battery.

I doubt the above are part of your current problem, but they will help to make things work better down the road.

Much of the advice you'll probably get will be directed towards the early K-bikes. Your profile shows you have a K1100LT which is a later K-bike. The wiring is similar but not exactly the same as early bikes so you may have to do some investigation.

The tail light's ground is shared between the BMU, running lights, instrument cluster illumination and headlight grounds. If those circuits are working, the problem might not be grounding. Have you checked for continuity between the tail light ground (Brown) and the battery negative?

Can you be a bit more descriptive on how you are testing the starter relay. There are four terminals to test. Look for 12V on the Red lead going to Pin 30 of the relay (the other large wire is Black). Voltage should be present at all time, irrespective of the state of the ignition switch. Check for 12V on the Black/Yellow wire going to Pin 86 of the relay with the ignition on, the clutch pulled in (or in neutral) and while the start button is pressed.

If your start button is not working you may have a kill switch issue [not uncommon], if you do then brake lights don't work. I have a habit of testing brake lights from time to time and on the K1100 kill switch must be in power on position ready to start the engine to get brake lights to operate. I expect they are related issue and its likely to be the right hand handlebar control [faulty kill switch] or the block connector into the loom.

I have 83 84 92 96/7 Ks and there are differences but thats for the K1100.

Thanks for the advice. The bike was running and riding well before the strip down. I have already cleaned all of the earths to bare metal. The entire lighting circuit is all good, the lights operate brightly. There is a constant 12v to the starter relay, from the battery, i can bridge the wire from the starter to the wire from the battery and the starter turns the engine as it should. I get 12v from the black and yellow wire to the starter relay, the blue and brown wire that should be an earth (via the ecu) is also receiving a 12v supply when the starter button is used. I have traced the black and yellow wire right up to the connection block from the right hand switch gear, it has 12v but very low amperage ( causes the test light to glow very dimly), volt drop somewhere along the black and yellow wire renders it to not having enough power (amps) to pull the starter relay in.

Maybe the brown/blue wire should be dropping to ground when the starter button is pressed. It seems from your checks that is is held at 12v (courtesy of the black/yellow wire via the starter relay coil) when it should actually be dropping, so's that current can flow and energise the starter relay coil?

Just to simplify, all else on the bike is working, horns, headlight, tail lights, instrument cluster, side stand switch, clutch switch, indicators. The only circuits that are not working are the starter motor and brake lights (i have given the brake light circuit an independent supply for now). The bike that i am referring to is a 1997 K1100lt ex police bike.

The start circuit is really simple.  The starter relay is supplied power either from the neutral detect circuit on the instrument cluster or the clutch switch through the start switch. Return ground goes through the side stand switch.  Something in the return path is not working, the suspects being:
- starter relay connections to Pin 85 & 86
- side stand connector and/or side stand switch itself
- wiring on Brown/Blue
- Brown wire on side stand switch.

How have you verified the operation of the side stand switch?
Does the neutral detect circuit work properly and does the gear indicator work?
Is the Motronic relay working properly?

Side stand switch is good, clutch switch is good. The brown and yellow wire at the starter relay gives battery voltage when operating the starter button, problem is that the brown and blue wire that sits next to it also gets battery voltage instead of ground, consequently, the relay is not pulled in to operate give power to the starter motor.  I have just removed and stripped the right hand switchgear, had it all nicely laid out on a table until my dog ran out after next door's cat and knocked the table flying. After spending the last hour or so looking for a small ball bearing and a couple of springs that seem to have evaporated, i have ordered a replacement from a local (ish) BMW new and used parts specialist. I will give it another go one of the days next week.

deleted

A little off topic (moi?) but does the Motronic not feature a starter lockout if revs are >850, like the ancient Jetronic does?

deleted

Tsk, Jetronic every time 

Seriously, cheers 

I wouldn't worry about the brake lights, I'd try to get it going first. I'd disconnect the extra wire you installed for the brake light, its masking a problem and making it more complicated.

The test light is dim at the starter relay.

I'd place the test light at the input side of the start button. If it's bright, but dim on the other side, your start button might be bad. If it's dim on the input side, I'd keep working back a step at a time, towards the battery.

Did you make some other changes? Cause this reminds me of a case where the green and green/blue wires were swapped in the right handlebar switch, by mistake, for example.

1brake lights issue may resolved itself once this is sorted.

But someone asking questions about the side stand switching possibly being an issue....remember a side stand issue also zaps the brake lights effectively underlining that it may be the cause

Point-Seven-five wrote:. . . if the start relay coil is getting 12v there is nothing but the side stand switch that will inhibit the relay from pulling in.

This diagram seems to indicate that in a '96 K1100 like stevieboy(sb) owns, a malfunctioning clutch switch or neutral switch can interfere with starting even if the side stand switch is working correctly. If there's 12V at the starter relay coil connection from the starter switch then the Motoronic relay might be faulty or there is some other wiring flaw. sb indicates the clutch switch is ok so seems to have attempted starting with the clutch handlever pulled in. It would be helpful for sb to put the year of manufacture and model of sb's moto in the Signature section of sb's Profile so it would show up with every post for clarification.

This post is using a genderless pronoun technique I'm developing to spare a perfectly useful set of existing English-language pronouns from abuse in workplace memos wherever problems with their usage might occur.  It's a little choppy but sacrifices must be made. 

deleted

That diagram that Laitch posted doesn't quite jive with the one I have.  The diagram I went from comes from BMW's SLP program.
Starter and Alternator
Legend

Excellent diagram!

The clown avatar is gender neutral btw.

daveyson wrote:I wouldn't worry about the brake lights, I'd try to get it going first. I'd disconnect the extra wire you installed for the brake light, its masking a problem and making it more complicated.

The test light is dim at the starter relay.

I'd place the test light at the input side of the start button. If it's bright, but dim on the other side, your start button might be bad. If it's dim on the input side, I'd keep working back a step at a time, towards the battery.

Did you make some other changes? Cause this reminds me of a case where the green and green/blue wires were swapped in the right handlebar switch, by mistake, for example.

Good point, the extra wire was not installed by me, it was already there, it is spliced in to the green wire from the right switchgear, i have no idea where it went, as i do not recall cutting through it when i removed the switch connector from the loom connector (maybe it wasn't being used). I will check the side stand switch etc as you suggest. I took the switch apart and it was extremely grubby on the contacts for the kill switch, i cant put it back together now though, the dog knocked the table flying yesterday and all of the little springs, ball bearing etc have leapt into a parallel universe  . New (second hand) switch coming on Tuesday. I'm having a break from it till then. It's a lovely day today so going for a ride along the coast road on one of my other bikes 

robmack wrote:That diagram that Laitch posted doesn't quite jive with the one I have.  The diagram I went from comes from BMW's SLP program.
Starter and Alternator
Legend

Thank you for that.

Laitch wrote:

Point-Seven-five wrote:. . . if the start relay coil is getting 12v there is nothing but the side stand switch that will inhibit the relay from pulling in.

This diagram seems to indicate that in a '96 K1100 like stevieboy(sb) owns, a malfunctioning clutch switch or neutral switch can interfere with starting even if the side stand switch is working correctly. If there's 12V at the starter relay coil connection from the starter switch then the Motoronic relay might be faulty or there is some other wiring flaw. sb indicates the clutch switch is ok so seems to have attempted starting with the clutch handlever pulled in. It would be helpful for sb to put the year of manufacture and model of sb's moto in the Signature section of sb's Profile so it would show up with every post for clarification.

This post is using a genderless pronoun technique I'm developing to spare a perfectly useful set of existing English-language pronouns from abuse in workplace memos wherever problems with their usage might occur.  It's a little choppy but sacrifices must be made. 

Thanks for the input. The clutch switch is working as it should, the neutral light is working, and so it the gear indicator, the side stand switch is also working correctly. I will start with checking all of the ground wires for continuity to earth and also note the resistance. You may refer to me as he, i'm a bloke, not a woke lol. I think it is a case of not seeing the wood for the trees, i'll start checking from the basics tomorrow at some point, it's far too nice a day to be tinkering in the workshop, off on a ride out on one of my other bikes 

robmack wrote:That diagram that Laitch posted doesn't quite jive with the one I have.  The diagram I went from comes from BMW's SLP program.
Starter and Alternator
Legend

I have just noticed on the diagram that you sent, it shows the ignition switch to have 4 positions. position 1 is "off", position 2 is "R",  position 3 is "on", then of course there is the position for parking light.  From the off position, my bike's ignition switch will only turn one click clockwise, indicating (according to the schematics)  that the ignition is in the "R" position, it will not turn any further, indicating that it is not switching to the "on" position. Is this a mistake on the schematic diagram, or does my ignition switch have a fault. The wire that someone who had the bike before me added (spliced into the green wire that comes from the right hand switchgear) maybe was added to provide an ignition fed live to somewhere due to the fact that the ignition switch will not turn to the "on" position?
Does your ignition switch turn to more than the one position?

My K1100 (1994) is the same i.e. ignition switch turn once to the right for fully on (ignoring the handlebar locking position).

Mike

robmack wrote:That diagram that Laitch posted doesn't quite jive with the one I have.  The diagram I went from comes from BMW's SLP program.

This is the cover of the manual from which that diagram was taken. There's a group of these manuals—ABS1-2, LE Jetronic, Motronic 2.1-2.2—in the Technical Library at Motobrick. Member volador uploaded them.

stevieboy63 wrote:You may refer to me as he, i'm a bloke, not a woke lol. 

I believe you.  Yours was just the post at hand for experimentation. 

My Clymer manual is wrong.  Disregard my previous posts in this thread.

stevieboy63 wrote:

robmack wrote:That diagram that Laitch posted doesn't quite jive with the one I have.  

I have just noticed on the diagram that you sent, it shows the ignition switch to have 4 positions. position 1 is "off", position 2 is "R",  position 3 is "on", then of course there is the position for parking light.  From the off position, my bike's ignition switch will only turn one click clockwise, indicating (according to the schematics)  that the ignition is in the "R" position, it will not turn any further, indicating that it is not switching to the "on" position. Is this a mistake on the schematic diagram, or does my ignition switch have a fault.

mike d wrote:My K1100 (1994) is the same i.e. ignition switch turn once to the right for fully on (ignoring the handlebar locking position).

Here's an excerpt from the K1100RT K1100LT Rider's Manual, copyright 1995. From what mike d and stevieboy are describing, there are two differing ignition lock systems. It isn't unusual for BMW to not update manuals because it is often revising models during their production life. These also might be continental differences.

Laitch wrote:

robmack wrote:That diagram that Laitch posted doesn't quite jive with the one I have.  The diagram I went from comes from BMW's SLP program.

This is the cover of the manual from which that diagram was taken. There's a group of these manuals—ABS1-2, LE Jetronic, Motronic 2.1-2.2—in the Technical Library at Motobrick. Member volador uploaded them.

I have been searching the interweb for K1100LT engine wiring diagrams and can only find two, one for 1993, and another for 1994 and later.  The diagram for 1994 and later has wire colors that match what the O.P. mentions in his posts and that is the one I based my questions on.

Neither of diagrams I found come close to matching the wiring shown in that illustration.  Is there a specific model identified for that diagram.  Is it possible that it shows the wiring for another model?  The manual title only mentions Motronic, and possibly may be generic.

Just dug out my original K1100 Handbook and guess what. It shows the same image as in as in Laitch's post above the switch and functions the same. However I've just checked on the bike and I don't seem to have the position that enables the parking light functionality with the key removed.

Probably not looked at that riders handbook since 1997 when I bought the bike!


Mike

Point-Seven-five wrote:Neither of diagrams I found come close to matching the wiring shown in that illustration.  Is there a specific model identified for that diagram.  Is it possible that it shows the wiring for another model?  The manual title only mentions Motronic, and possibly may be generic.

The table of contents, and notes on pages by one of the manuals previous owners, seem to indicate its relevance to both the K1100 and the R1100RS which share certain Motronic functions. Maybe somebody here who owns a '95 or later K1100 can confirm that its fuel pump primes with the side stand down but that it can't be started unless the clutch switch or neutral switch is activated. That would confirm the diagram. I'm just the messenger. 

"...after testing them (starter relay wiring) with the test light, the clocks remain lit up...even with the ignition off...they do however turn off again if I switch the ignition on and off again"

Stevieboy, I'd look at and clean the ignition switch (in a bucket type thing, in case bits pop out)

Until you get the new kill switch and start button, an option would be to bypass them with jumper wires.

Laitch wrote:

Point-Seven-five wrote:Neither of diagrams I found come close to matching the wiring shown in that illustration.  Is there a specific model identified for that diagram.  Is it possible that it shows the wiring for another model?  The manual title only mentions Motronic, and possibly may be generic.

The table of contents, and notes on pages by one of the manuals previous owners, seem to indicate its relevance to both the K1100 and the R1100RS which share certain Motronic functions. Maybe somebody here who owns a '95 or later K1100 can confirm that its fuel pump primes with the side stand down but that it can't be started unless the clutch switch or neutral switch is activated. That would confirm the diagram. I'm just the messenger. 

Fuel pump does NOT prime if side stand is down.

It must be retracted.

To me that's in agreement with the drawing. What's wrong with the drawing Laitch posted? Whats wrong with the Clymer drawing, or any other?

daveyson wrote:To me that's in agreement with the drawing. What's wrong with the drawing Laitch posted? Whats wrong with the Clymer drawing, or any other?

The Clymer drawing as well as the BMW drawing that Rob posted show the ground connection for the start relay going to ground past the "fuel injection"/"Motronic" relay ground terminal and through the side stand switch.

The drawing that Laitch posted from the BMW Motronic training course shows the side stand switch in the +12v side of the start relay circuit while the start relay is connected to ground through the clutch switch or the "Gear Box Switch"(?).

In order to troubleshoot why the start relay isn't working it would be useful to know if the side stand switch is supplying 12v to the relay, or if it is completing the ground connection for the coil.  It makes a lot of difference in what we are looking for as we poke around the wiring.

This, to me, is sort of important since the fact that the bike has 12v on the ground side of the start relay when the start button is pushed says that there is a bad connection to ground.  In order to work, that voltage should be very near zero, and we need to find why that connection to ground isn't being made. Without the correct drawing we have no idea where to look.

So I'm thinking Clymer is also right as an earth goes from the sidestand switch to the gear switch.

Since the drawing Laitch posted relates to motronic, I'll guess their summary skips the sidestand, and considers it more relevant to the frame wiring.

Anyways, I've been thinking there is an earth failure, but also a power fail indicated by the dim test light result. I'm thinking the Amps are too low, so thought keep testing back in steps towards the battery to find where the power problem is.

Or maybe skip those steps and go straight to the ignition switch.

Is there any merit in this idea for Stevieboy?

daveyson wrote:Anyways, I've been thinking there is an earth failure, but also a power fail indicated by the dim test light result. I'm thinking the Amps are too low, so thought keep testing back in steps towards the battery to find where the power problem is.

Or maybe skip those steps and go straight to the ignition switch.

Is there any merit in this idea for Stevieboy?

Thank you for your input, replacement righthand switchgear coming tomorrow, i'll trace everything back to the battery, once i have the switchgear plugged in

Sorted!! Side stand switch had two wires and worked as it should, ie, continuity between the two wires when the stand is up, open circuit when it is down (one wiring diagram shows 3 wires, another only two ). Anyway, i simply connected an earth wire from the main frame earth point to the Blue and Brown wire at the starter relay. The starter circuit now works as it should, fuel pump powers up and brake lights are working. I'll get some fuel tomorrow and hopefully run it up. Thank you all for your suggestions, they were very helpful.

Bonus, that's progress, but that's masking the problem rather than fixing it. It would be good to know why the relay is not being supplied with earth when it should.

The starter circuit isn't working now as it should cause you have constant earth to the starter relay, overriding the motronic ability to deny earth when the conditions aren't right.

Daveyson, the Motronic doesn't supply the start relay's ground. It's connected by wire to the frame along with the Fuel injection relay through the sidestand switch.

True, I was looking at the diagram while you were posting to make sure I wasn't talking bullshit, I was, just tried to delete it, but you beat me to it.

A bit surprised about that, a bit of a step backwards compared to the LE Jetronic, I think.

I guess you agree though stevieboy has masked the problem rather than fixing it.

Stevieboy, am I right in assuming you installed your new switches and that you still had the same no start symptoms, and then you made the direct earth connection to the starter relay?

daveyson wrote:True, I was looking at the diagram while you were posting to make sure I wasn't talking bullshit, I was, just tried to delete it, but you beat me to it.

A bit surprised about that, a bit of a step backwards compared to the LE Jetronic, I think.

I guess you agree though stevieboy has masked the problem rather than fixing it.

Stevieboy, am I right in assuming you installed your new switches and that you still had the same no start symptoms, and then you made the direct earth connection to the starter relay?

Yes, that is correct. I have not masked the problem, it is fixed and everything is working as it should. Apart from me providing the earth to the starter relay, the wiring is how it left the factory. There was nothing wrong with the original switchgear, at least there wasn't until the dog knocked the table over when i has the switches in bits, loosing a couple of springs, a ball bearing and a plunger lol.

daveyson wrote:Bonus, that's progress, but that's masking the problem rather than fixing it. It would be good to know why the relay is not being supplied with earth when it should.

The starter circuit isn't working now as it should cause you have constant earth to the starter relay, overriding the motronic ability to deny earth when the conditions aren't right.

The motronic does not supply the earth. The wiring colours on my sidestand switch do not correspond with the colours on the schematic either. Remember that this was a police motorcycle, it may have been wired different so that it could start with the side stand down, maybe so that flashing lights etc could be operated with the engine running, stand down, so as not to drain the battery? It is also fitted with a 70 amp alternator. When I acquired the bike, it still had the flashing blue lights, sirens etc fitted, i actually had them all going when it broke down in the outside lane of the M5 Motorway at 80mph, when i was riding it home on the day i purchased it. Saved my bacon !! i had to cut across three busy lanes and an entry slip road, in order to get to the hard shoulder, in congested traffic, with the engine not running. All police gear has since been removed, by myself.

Yes,  I see your point. But with permanent earth to the sidestand you have lost the safety feature of the starter disabled while the side stand is down, that's a guess. But when the engine is at idle, the starting circuit is bypassed, so then yes it will idle with the side stand down.

We still don't know why there is an earth failure to the relay. It might be worth checking to see if the test light is still dim with the test you did.

I think a few of the symptoms are pointing to a problem at the light switch. I'm guessing you have a light switch on your right handlebar.

What are the wiring colours on the sidestand?

daveyson wrote:Yes,  I see your point. But with permanent earth to the sidestand you have lost the safety feature of the starter disabled while the side stand is down, that's a guess. But when the engine is at idle, the starting circuit is bypassed, so then yes it will idle with the side stand down.

We still don't know why there is an earth failure to the relay. It might be worth checking to see if the test light is still dim with the test you did.

I think a few of the symptoms are pointing to a problem at the light switch. I'm guessing you have a light switch on your right handlebar.

What are the wiring colours on the sidestand?

The test light is no longer dim, the light switch is fine and all is working as it should. I am aware that the sidestand safety feature is no longer there, but i was brought up on old bikes with zero safety features and my post classic superbike racing Honda cb750 isn't exactly safe around the Isle of Man TT circuit either (single pot callipers up front, drum on the rear and has gone through the speed sensors on the Sulby straight at 168 mph). I think i will cope, i will sort something out on that score if i come to sell the BMW though ( i'm planning to keep it though). I cant remember off hand what colour the wires were (are) and i have taped them up with self amalgamating tape now ( I was involved in a bad motorcycle accident in July 2019 and had a traumatic brain injury as a result, along with 9 broken ribs, flail chest, fractured pelvis and broken wrist) so my memory is shite now, which is why i struggled a bit with the wiring problem, my concentration levels are very low. I spent 30 years of my life restoring classic Ferrari, Mercedes and jaguar xk's E types, Mk2's etc, and now i struggle a bit.

stevieboy63 wrote:The test light is no longer dim, the light switch is fine and all is working as it should. 

Except the side stand safety switch isn't working as it should. Like you assert, maybe police motos enabled starting with the side stand down for some reason unfathomable to mere civilians. Member jbt has experience in law enforcement with these motos; maybe he could shed some light on this.

What I'm interested to know is if the moto will crank—or at least lurch— if starting in gear is attempted.  It seems that your work would breach the clutch safety switch too.