Help! I'm posting in electric because the problem seems like an electric one. The topic just about says it all. '85 K100RT (stripped of the fairing). Engine will cut out while running, for just a split second, occasionally, not very often at all and usually does not happen on a run. Engine will run perfectly and then not start, sometimes. This might happen when the engine is hot or cold. Console lights come on and are bright when I turn the key. Headlight is on and bright. When it happens, I wait and it starts up and runs perfectly. One time, I left it where it was, went home and came back the next morning and it started. The other time, today, I waited just a few minutes and it started and ran superbly after trying several times to start it. But, while it was idling, it died like somebody turned off a switch, but started right up again.

I hesitate to mention it because I believe it is just a coincidence, but, today, I shifted into first, clutch pulled in, to try starting it and it started. This was after trying to start it in neural.

The kill switch assembly has recently been replaced as it was causing "stopping" problems.
The ignition switch has also recently been replaced.
Spark plugs changed about 1000 miles ago.
Fuel filer replaced at same time as spark plugs.
Fuel tank emptied and cleaned.

When engine cuts out, it's like a switch is turned off, no sputtering, etc.

One time when it would not start, I pulled the fuel line to the injector rail and cranked the starter; fuel pumped out. Still would not start.

I thought maybe there's a short somewhere but wouldn't that be a consistent problem, at least when I am sitting there, waiting to try starting the engine again?

When it happened one time and then started, a friend put a spark tester on the wires above the injector rail and said #1 was running erratically. It was idling kind of rough at that time. He was thinking maybe the wiring harness there (at least the wire to #1) was bad. Would that cause the engine to quit, or not start?

I really appreciate any advice and/or guesses about this.

I'm having hip replacement surgery in a couple of days and won't be able to ride for awhile so solving this problem will keep me busy until I can get back on the bike.

Thanks to all,

Dennis

Gees dennis we are worse than the bikes, we are all falling to bits. The doc wants to do a knee on me but I am holding out for the time being.

It sounds to me like an intermittent open circuit at a plug probably but of course where is the question. With a K100 or 75 it is difficult to run them with the tank off the bike and so play with the connectors.

I have experienced a fuel pump that would cut out very suddenly but almost immediately restart.

The first instinct is something electrical because fuel problems usually splutter a bit but a pump is both.

The plug which is on the lead comming from the tank has in the past proven to be one of the main offenders, the female part opens out causing a very poor electrical connection.

I think the bikes have one up on us, if our pump stops we can't just replace it easilly and I think my ECU has seen better days too.

wow dennis ......is this a test ?

welcome to the forum old mate .

there are lots and lots of electrical connections on these old ladies , in comparison to many other machines at the same year of manufacture ....dont forget these things were one of the first to incorporate electronic fuel injection in production motorcycles.

it kinda sounds to me like you have a few issues ...that surface ...every now and then ...just to confuse you .

if i can suggest ....look at the portal page ...(when you get a few posts up) your looking for the "troubleshooting efi page" .

in there you will find a sequence list ...and to my way of thinking a good place to start to account for all the subsystems that make the whole thing work so well ,, when all good.

having said that .....our old gals suffer from the dreaded corrosion problems ...of age ...more specifically electrolisis across connections ...rubber that is past its "use by date" by 10 years or more, neglected maintenance , and just the fact thats its a bike and open to every bit of spray off the road that there is .

there is also a list of logical things that should be done in the "you just bought a k100 now what ?" section .

strongly recommend a good read of that, if you havent already done so .



but in this case ....without any condition report ..i would be looking at the under seat connections to the injection control computer and the primary and secondary coil connections and on towards the plugs, given that you have changed them anyhow .

i have experienced first hand failing plug leads one of which caused both cylinders to fail at the same time ( double ended coils btw ) and this might be a contributing factor .



in case you havent found it yet the primary of the coils should measure between 1.9-2.4 ohms (no less ) secondays of the coils from socket to socket should be about 10-12 k ...no more ,,and plug leads end to end about 2-5k depending on length .

to me it sounds like atmospheric conditions are changing the way that things are happening ,,,and that points to corrosion somewhere,



good luck !!!



theres lots of wise folks here ..(pity im not one of them) but just trying to help out where i can ,,


just saw k freaks suggestion .....and that is definatly ...on the list ....happened to me more than once till i found it .


cheers



additional note ..... check your crankcase breather pipe ..(hidden behind the ignition coils and connects to the intake plenum at a weird angle ) this might give some interesting behaviour ...given its state of seal and movement due to vibration etc .. in fact check all the rubbers along the intake path , vacuume bleed seals etc .

Does this only happen when warm? If so it could be the Hall effect sensors. Always worth checking the tank connector for good connection although you note that once it was pumping fuel OK. Worth checking the fuel pressure is correct (around 36 psi) when running, also worth checking for air leaks around the induction system since stray air getting in will cause rough running.
Regards,
K-BIKE

Thanks all. I'll get on all the suggestions as soon as I'm mobile enough to get outside and work on the bike.

K freak: Yeah, our parts are not too available. The pump: I had bypass surgery a couple of years ago. I figure it's all bonus time now. The ECU? No replacement possible...ha ha!

Yesterday, when it would not start, I had been reading about how troublesome corroded electric connectors could be a problem. I took apart the one under the seat on the right side, 4 pins I think. It was corroded and lots of dust flew when I took it apart. I didn't have anything to clean it but I plugged it in and out several times. The bike didn't start. After waiting a few minutes the bike started. Today, we took a long, all day ride and she ran like she wanted to, no problem at all. Is it possible that the connector was the problem and it didn't start because it was flooded?

Oh, and why, all of a sudden, while riding, the red brake light on the dash blinks along with the right directional signal (but not the left). I have vowed not to go crazy with the electrical silliness of this wonderful old bike.

lol dennis ...just minor gremlins .....

the rear brake light is usually the problem ....it just sits there for years and years ....replace it mate ....clean the contacts ....dont forget the earth connections at the back of the globe holder also .... do the indicator as well .....the contacts that join the globe to the holder often vibrate for years and wear the solder connections at the base of the globe

Could be an idea to check the ground connection at rear right flasher.

The 4 four pin connector you did find is probably the tank connector and the power feed to the fuelpump,
give it a good clean and some protection spray, to avoid later problems.
DeoxIT seems to be the magic word on this forum.

Inge K.

Went for an all day outing yesterday with lots of stops and starts. Took a longish trek this afternoon. No problems at all. She's running great. (Hope I didn't just jinx it).

I'm 5 days back from hip replacement surgery and running like a 26 year old motorcycle. Well, maybe not that good...
I was able to get out to tinker with the bike, raised on jacks, and she started and ran just fine.
The radiator fan is making some hellatious noise. I had thought it was a little leak in the cooling system. It had been intermittent and only under high heat conditions. Having the bike up on jacks lets me have a better look and it is clearly the fan. It sounds like the fins on the fan are hitting something. It had sounded before, like a whining sound. I'm thinking the bearing has gone (whining sound) and now the fan is wobbling because the bearing isn't keeping it in it's rightful place. Sound about right? Are these repairable? Or, true to BMW tradition, will I have to purchase the whole unit brand new in order to further line the pockets of the best economy in the world?

In case anyone is thinking about hip surgery, I have NO arthritis pain. It is gone! Some pain from the surgery of course...

very pleased to hear you are feeling better for having the surgery Dennisg.
i read recently that if left go these fans will chew into your radiator, also you can purchase the fan motor as a seperate entity. Bosch part # 0 130 007 027(thank you Kfreak)
Mine had a collapsed brush, now i have a new fan and an old fan with one brush spare.
N.

dennisg844 wrote:It sounds like the fins on the fan are hitting something. It had sounded before, like a whining sound. I'm thinking the bearing has gone (whining sound) and now the fan is wobbling because the bearing isn't keeping it in it's rightful place. Sound about right?..

It also could be that you lost the clip on the front of the axle, then the fan is able to work itself away from
the axle and start touching the radiator.
Check it out before it do any harm to your radiator, and good luck with your hip.

Inge K.

the original fan on mine was a press fit , no c clip , couldnt budge it , but yours could have chewed out and now floats, should be an easy diagnosis, there is a link on here called "heat management" in which a gentleman shows us his fan mod using a smaller , cheaper fan with a higher through put of air , i reckon this is the way forward, a man could make a bob fabbing them up.

Have tried to find back the thread where did see this clip some time ago...no succes.
Could be that a clip have been fitted on later models to prevent that the fan could move of the axle.
Or it was someone done a modification on the axle to accept a clip.

But while searching around....it`s some threads out there about the fan moving on the axle.
Here is one of them.

Inge K.

I got it all apart and it is clearly the fan motor. The spindle is rough to turn and wobbles around. I'm going to go with the motor replacement. Thanks for the tip beanoldboy. I'll let you all know when it's back together.

Good to hear all is well with your hip Dennis.

Those fans are a continuing problem because of exposure to the elements. I use the optimol grease on the bearings and plenty of it to seal the water out and each time the system is drained I do it again. It seems to work as I don't have problems anymore.

Thanks K Freak. Dare I say, Hip Hip Hooray? No, that would be too...