Gents...My 85RT went into electrical convulsions. Riding, doing a few errands yesterday, the last nice day this fall I'm afraid. Made a couple of stops, rode a total of 45 minutes and at last stop bike would not start. (oh s...) Here are the symptoms; Thought is was dead battery but then realized the instrument lights were on but faint and pulsing. The LCD gear indicator pulsed on/off. The tach goes to 5k and sticks. Turned off key and retried and heard faint buzz or clicking from starter location and then all was dead. Retried and have same symptoms each time. I have 12.5 volts on battery when all is off. I searched through the topics and did not see this type of symptom described. I have Berts electronic system troubleshooter printed off and will go through that step by step, but was wondering whether the symptoms described may give a hint to which component is faulty. Thanks in advance, keith

did the bike start up quickly or sluggishly before you went for ride ? may of been low battery and the relay fused leaving the starter jammed on or the sprag clutch may need cleaning
check what the starting voltage drops too as well may be a dead battery

cheers Tony

whilst measuring the battery turn on the ignition , if the volts drop markedly (1.5 -2 volts ), you have your answer .

batteries measured without load will always give you a false reading .

inspect the fluid in each cell ...if you have lost a lot of fluid on the most positive cell , looking to see if the plates are exposed , probably it has been over charging ....do you use a battery tender ?

+1........Charlie.

If the battery is good, check battery connections...check both ends of ground.

If OK, next suspect would be the ignition switch.

To check, disconnect the ignition switch connector under the tank....and jump the red and the green wire at the harness connector.

All of the above, but I think my money would go on a stuck starter solenoid although a bad earth can cause some really strange effects.

Does the K100 have the earth underneath the battery tray? That might be worth looking at.

Best of luck...

+1 Gerry
I would undo the earth connection from the frame. My bike had all sorts of crud under the cable end and around the bolt that I couldn't see just by looking at it. Unbolt it and wire brush it at least. ( De Oxit is our favourite connection cleaner).
Good luck, that is a terrible feeling when it drops you in it in public.
RT

Thanks to all. Totojp it started normally, fired right up. Charlie, i will check voltages tomorrow (bring her home from temporary housing) and let you know. Yes I use a battery tender, 2amp. Sealed battery.

Inge, Thanks as always, an IPA and smoke for you. Could it be a load shed relay going bad? GerryP, mine has grounds to frame below battery, frame under tank and at front fairing (instruments). RT, I am pretty certain I have good earth contacts. Charlie had advised me earlier in summer and I used a deoxit type product. Not too embarassing to not start in public, (I have had far worse occur) just a bummer cause she has been running and riding fine all summer. Thought she was "charmed"

kfilipow wrote:Could it be a load shed relay going bad? GerryP, mine has grounds to frame below battery,

Normally the battery ground is at the LHS of the gearbox, but it`s not that important......if you got a good electrical connection between the frame and the gearbox.

A bad LSR wouldn`t cause problems like you got, but it would affect headlight, flashers, horn and fan.

ouch ... a sealed battery . that will make it quite difficult to check the levels and in need be toped up ....

have a close look at the top of the battery if you know its a lead acid type ...quite often there are infact filler holes under a cap of sorts ,,moulded into the outside of the battery casing ...almost undetectable at first glance

personally i would only use a tender once a month for topping up and only for a day at a time .....the constant high voltage (although verry low current ) creeps up high like 14 + volts causing burn off of the electrolyte (bubbling) this changes to gas and escapes the cell ...this generally happens on the most positive cell . take note this also happens in agm batteries ....i have personally replaced hundreds that are dead in alarm system panels ...they measure fine for about 10 seconds when under load then just drop off the planet ..they dry out ...for the same reason above .

i believe there are specific tenders that switch off ..when not required ....but nearly all that i have seen dont ...

The earth below my battery tray bolts to its underside and you can't see it until you try to remove the tray.

It runs into the main loom and is in addition to the other earths (gearbox and under tank).

It exists on the first Motronics k-bikes (without oxygen sensor) but I'm not sure about the others.

(edit: definitely not on k-jet tronic bikes)


One other simple thing - try giving the starter motor a tap with a hammer/tommy bar. This might free up sticky brushes if thats the problem. (Not too hard ) If that works you'll need to replace the brushes some time soon.

From the symptoms I would say flat or dud battery because of all the other symptoms.
Regards,
K-BIKE

To K-bike and others, many thanks for the input. Seems to be failed battery. It is a sealed battery Charlie. So I will judiciously use the tender from now on. Batteries here are about USD 150 for good 25-30 amphour. That's two weeks of allowance so hopefully it will be replaced tomorrow... (College tuition for number 3 is due for spring semester, she gets first dibs on extra cash) I will keep all posted.

My bike died too, outside 'Gearbox', a local bike accessory store just 10 mins away. I only went in for a tail light bulb (and a chat) Five mins at the most!! Came out, fitted the bulb, jumped on...nope . Acted as cool as i could in front of the other 6 or so bikers shopping there (bearing in mind i'm new to all this biking stuff)!!
Anyway, they did have a new battery behind the counter £65.00 29amphour. Great i'll take it and fit it outside .
'eerrr, sorry mate they come dry nowadays, the acid is in the box then you'll have to charge it for 3-4 hrs . I'll put it to one side for you, come back tomorrow for it, jump on the bike i'll give you a push'

That's customer service for you. As was doing my lid up he said, 'i've owned two Ks in the past so i know '
Not sure what he meant really .

G'day All, A while ago had this problem with the K75 where, whilst riding, the ignition would fail.The instrument warning lights would come on but only dimly. All the other electrics like headlight stayed bright and the horn,indicators and brake lights still worked.Inge, in a recent post suggested that the ign.switch can be checked by jumping the red and green wire at the switch harness.This I guess has the effect of bypassing the switch.So my stupid question is that to do this check is to wait until the ignition cuts out,leave the ign.switched on and then unplug the harness and jump the wires. If ,after jumping,the ignition lights become normal, it must be the switch.........My gut feeling is that the switch is faulty but...you never know.Any comments would be great.Thank heaps in advance.And Inge I reckon we owe you a carton of JBP beer.Cheers Tom Grabau.

Along the road it could be easier to remove the crash panel, and short the red and green wire at behind of the ignition switch.....
Depending on how it is possible to acces....wire length etc... you have to check,
then you could remove the cover at the rear of the ig.switch in forehand.

Have a look at this link.

It could also be the ig.switch connector that is the problem,
but usually it`s the switch internals.

When the fault did occur, did you try to wiggle the key a bit forth and back?

Thank You Inge,I have wiggled everything possible back & forth to no avail.Next time the fault happens,I will jump the red and the green wire behind the switch.It is easily accessable. Thanks again and I will keep you posted.Cheers Tom Grabau

Intermittent electrical faults are the worst

I was embarrased once by nudging my kill switch (under the start button) and not noticing. It only has to be a small amount off vertical to stop the engine. The results on the instruments look quite strange if you're not expecting it and I had the tank off the bike doing continuity testing in the relays before I spotted that switch

I think I would be annoyed enough by this stage to lift the tank and pull each piece of the ignition system at at a time cleaning and testing as I went. The ignition switch is a good place to start.

Best of luck.

Thanks GerryP,Next time the fault occurs,the jump test will be done behind the switch.I will keep you posted.Just have to remember to carry some wire with alligator clips attached. Thanks for your inpuit.Cheers Tom

G'day All, Started the 75 today and after a shart time idling,conked out.Jumped the Red wire to Green wire at ign.switch and all inmstrument lights brightened up as per normal.Ign. switch therefore needed attention.Pulled the switch apart according to Inge's link which was fantastic.Cleaned all the contacts and all is good so far.Will report back if the problem happens again. Thank you all for your help. Cheers Tom.

No mention of the carbon brushes in the starter. When these wear out, the whole electrical system loses ground and behaves as described. Been there done that. How many miles does this bike have? A failed starter switch generally manifests itself when you try to start it and it doesn't, not so often mid ride in my experience.

As an aside, BMW just sent me a brand new ignition switch for a bike I bought new in 1984, keyed to the existing keys. It only took two weeks. Man, you cannot complain about service like that! If you buy a new switch, be careful when ordering to get the correct switch for your bike's production date. Somewhere in 1985 there was a change to the electrical connector. I didn't catch that little detail when I ordered my switch, nor did the parts person at my favorite dealership, so I had to improvise a pig tail from an old wiring harness and my old switch. Alls well that ends well, but just something to pay attention to.

Themason wrote:No mention of the carbon brushes in the starter. When these wear out, the whole electrical system loses ground and behaves as described.

To say that the whole electrical system loses ground, is stretching it a bit to far.
It`s only the Load shedding relay coil that is grounded through the starter (brushes).

And it indeed wasn`t the the problem in the last posts of this thread, as the only equipment that did function correctly when the problem arised, was the equipment that is connected through the LSR.

BTW. the ignition switch connector was changed in 04/85.........
a lot of connectors in the wiring was changed during -85.

[quote="Inge K."][quote="Themason"]No mention of the carbon brushes in the starter. When these wear out, the whole electrical system loses ground and behaves as described.[/quote]
To say that the whole electrical system loses ground, is stretching it a bit to far.
It`s only the Load shedding relay coil that is grounded through the starter (brushes).

And it indeed wasn`t the the problem in the last posts of this thread, as the only equipment that did function correctly when the problem arised, was the equipment that is connected through the LSR.

BTW. the ignition switch connector was changed in 04/85.........
a lot of connectors in the wiring was changed during -85.[/quote]

It is not stretching it a bit. When the carbon brushes wear out, lights dim, flash on and off, brake somehow operate turn signals, turn signals make all the lights flash, and the bike will stall and not start at traffic lights.

When this was happening to my bike my friend from BMW asked me how many miles the bike had and if I had, then told me to change the carbon brushes. When I removed the brushes from the starter, they were completely worn out. Replacing them solved the problem. The carbon brushes indeed affect system ground.

G'day All, my 75 has travelled about 68000Km and the starter brushes were checked about 18 months ago-they seemed to be fine.The bike only had the ignition problem and was always easy to start. Will keep you posted as to how good the switch repair was.Thanks again Tom

good work tom ..got my fingers crossed for you

G'day Charlie, thanks for that.Funny dealing with Inge's Link, how some of the old german lingo crept back into my mind.Hope Ulrich goes OK with the broken shockie stud. Cheers Tom

Themason wrote:

Inge K. wrote:

Themason wrote:No mention of the carbon brushes in the starter. When these wear out, the whole electrical system loses ground and behaves as described.

To say that the whole electrical system loses ground, is stretching it a bit to far.
It`s only the Load shedding relay coil that is grounded through the starter (brushes).

And it indeed wasn`t the the problem in the last posts of this thread, as the only equipment that did function correctly when the problem arised, was the equipment that is connected through the LSR.

BTW. the ignition switch connector was changed in 04/85.........
a lot of connectors in the wiring was changed during -85.

It is not stretching it a bit. When the carbon brushes wear out, lights dim, flash on and off, brake somehow operate turn signals, turn signals make all the lights flash, and the bike will stall and not start at traffic lights.

When this was happening to my bike my friend from BMW asked me how many miles the bike had and if I had, then told me to change the carbon brushes. When I removed the brushes from the starter, they were completely worn out. Replacing them solved the problem. The carbon brushes indeed affect system ground.

Worn out carbon brushes will not cause the bike to stall of will it cause a fail to start problem other than the brushes preventing the starter from working. The ignition or fuel injection systems do not use that earth.

Themason wrote: It is not stretching it a bit.

In my opinion it is, when you say "the whole electrical system loses ground".
When in fact it is only LSR coil that loses its ground connection.

Themason wrote: When the carbon brushes wear out, lights dim, flash on and off, brake somehow operate turn signals, turn signals make all the lights flash,

All this equipment (and more) got the power supply (not ground) through the LSR.....when the contacts stays closed.

Themason wrote: and the bike will stall and not start at traffic lights.

Worn starter brushes would not cause the bike to stall.
But it could be that you allready got a weak connection in your ignition or injection system somewhere, which makes it sensitive to the constant varying voltage when the LSR is rapidly kicking on and off.
Certainly the bike gets difficult to start, when you got worn brushes....the power supply to the starter isn`t sufficient.



The purpose for the LSR is to cut unnecessery consumers when the starter is turning,
to get maximum power available for the starter.
The negative side of the LSR coil is connected at the starter power supply wire.

When the bike is running the LSR coil is grounded through the starter brushes, and the contacts stays closed.
When you push the starter button you get a positive feed in the starter power supply wire, and the LSR coil loses its ground connection and open the contacts.