OT - Intermittent ignition failure on K bike

motoyoyo · 04-30-2004, 11:18 AM

I recently sold my K75S to someone locally and there is an ignition problem that has reappeared. I'm convinced that the bike is just trying to come home, but I need to get this figured out one way or the other.

What is happening is the entire ignition including most of the instrument panel lights will periodically go dead after the bike has been stopped. This has never occurred while the bike is already running or being ridden. It only occurs on occasion after the bike is shut off. What I have been able to discover is that if I put the bike in 3rd or 4th gear and roll the bike forward or backward turning over the engine slowly with the ignition on, I can get the ignition and instrument lights to come back on. The bike will now start like normal. I can also always bump start the bike and it will run fine.

I had taken the bike in to the dealer about two years ago for this problem and it they appeared to have fixed it, however it is back now. I'm not sure what they did to fix it, but apparently it didn't last long. Could this be starter solenoid related? Would that affect the ignition and instrument panel like this? BTW, the headlight, tail light, turn signals, horn, instrument panel back light all work fine. The choke light, battery light brake fault light, and neutral light do not function when the ignition is not functioning. There is a new fully charged battery in the bike too. Anybody have this happen before?

roger albert · 04-30-2004, 01:55 PM

Doesn't sound solenoid related, but I know K-harness much less well than R.

Look at the circuit to/from the kill switch. The things you mention 'going away' are wired to that same switch circuit. I assume whenever the bike is deas, you have no power to the coils?

Start trouble shooting be identifiying the wires to/from the kill switch.
Definitely where I'd begin. Spray contact cleaner in the switch while workihg it. Also wait for a failure and then try starting it while the swtich is still wet with cleaner. See if there is a change in behavior.

motoyoyo · 04-30-2004, 02:41 PM

Roger, I just checked with the shop that worked on it last time this happened, which was only about 2k miles ago. They replaced the carbon brush set and brush holder plate in the starter motor. I'm not sure if they replaced the armature or not. The problem went away completely, but has now resurfaced after a year or so of the bike sitting without being started.

It probably isn't kill switch or general wiring related since I can get the problem to occur or go away just by rotating the rear wheel while in gear. It seems to be isolated to the starter motor again even though it was rebuilt previously. Just wondering why it might reoccur unless there is another part in the starter that might be causing the problem.

roger albert · 04-30-2004, 02:49 PM

Interesting and odd. Normally, that would sound hall-sensor is, but it doesn't make sense that that would take out the lights you listed. I'll have to dig up a K diagram.
More later...

bbq_duck · 04-30-2004, 03:02 PM

yep... had a 85 K100RS.. same problem... same fix as motoyoyo

bike was under warrenty at the time... shop just did the whole starter

had them scratching their head trying to figure it out, but thats what it was

motoyoyo · 03:14 PM

To make it even more weird, I just tried it again by moving the bike in gear. Now the instrument panel lights don't come on at all including the gear indicator, but it will start if the starter is in the right position. You can tell when it is going to work because the fuel pump will pressure up the way it should when you first turn on the ignition, then the starter button will fire up the engine. Hmm, maybe it is in the ignition since the instrument lights aren't coming on at all now even when it's running. I'll go through it with some contact cleaner and see if anything changes. Thanks for your input Roger.

Just saw your post bbq_duc, that's good to know someone else has seen this before. Do you know if they replaced the whole starter or just rebuilt it?

bbq_duck · 04-30-2004, 03:29 PM

total replacement.... under warranty... they said the arm was shorted out... same thing about starting it, it depended on the position of the starter...

Beemuur · 04-30-2004, 05:02 PM

This may sound far fetched and memory may not be serving me well, but I used to have an 85 K100 and I recall a path to ground through the starter. Although I never experieced the problem.

Beemuur · 04-30-2004, 05:44 PM

http://skylands.ibmwr.org/tom/tech/starter.html

motoyoyo · 04-30-2004, 08:08 PM

Thanks for the info John. That's exactly what I'm experiencing. The part that bothers me though is that I had the bike serviced at my local shop about 2k miles ago for this very problem. I spoke with the shop today and they said they completely rebuilt the starter and put in new brushes and brush plate. It really should have lasted longer than that before needing service again. Not too sure if I want to take it back to the same place for the same problem now.

Strange situation I'm in with this bike. I've sold it to a local guy I've never met before, but I really want to make the bike right for him. I sold it under the premise that it was in great shape, which it is other than this problem. Looks like I'm going to give him a call and have him bring the bike back to me so that I can spend the day working on it. Wow, I guess I really loved that bike after all. I even offered to buy it back from him just so I could make sure it was ok. Sheesh, I'm pathetic!

Don Ro · 04-30-2004, 09:20 PM

"Sheesh, I'm pathetic!"
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Maybe you're just a good guy. I don't like to sell something that's not right - unless it's mentioned in the deal.
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Will he sell it back to you?
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Best,
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motoyoyo · 04-30-2004, 10:51 PM

Quote:

Originally posted by Don Ro
Will he sell it back to you?

No, he loves it anyway. I told him I'd buy it back any time in the next month if he wants his money back. We decided that the bike is just trying to get back home, since it was my baby for 16 years. He said he wanted to stay in touch and ride sometimes, so that my bike could see me once in a while.

Lorenfb · 05-01-2004, 01:58 AM

I had a problem like this on my K100. It was the #15 line thru the ignition switch
which was intermittent. BMW runs the coils' currents (amps) thru the ignition switch.
I added a relay to off-load those currents from the ignition switch. This solved the
problem.

brad black · 05-01-2004, 06:28 AM

they earth the head light thru the starter motor, so when you press the button the 12v at the +ve side of the starter cancels out the 12v in the headlight circuit and the headlight goes out. just one way to turn the light off when cranking.

not that it helps your problem. they did some wacky stuff with the electrical systems on them. turning it over in gear sure sounds like it's starter related to me.

roger albert · 05-01-2004, 06:44 AM

Yes, they did a bunch of funny stuff.
Loren's tip on the ignition wiring is a good one. It's starting to sound like an armature wear (or open contact) problem. If the contact was marginal back before the first repair, new brushes could have brought it back to functionality. After the brushes wore some, they were no longer able to make good contact with a (likely) increasingly worn/intermittent armature.
Just a theory, I don't know.

I was up until about 3 am trying to work on a triumph I got roped into checking out (electrics problems too) and thus haven't had a chance to look at your problem yet.
I'll try, as time permits

motoyoyo · 05-01-2004, 07:16 AM

Thanks for the input guys. I'll include the #15 wire through the ignition on the list of possibles. From all of your descriptions of this electrical system it's starting to make sense now. It's just plain whacked from the get go. Everything about it seemed opposite of how it should react, but I guess it was intended that way.

I tend to agree with Rogers deduction about the armature being the possible culprit. Since the problem was temporarily fixed by addressing some of the starter parts, then it is likely still located there. The armature was probably not replaced, but I'll check with the shop again. Thanks

roger albert · 05-01-2004, 10:16 AM

what year is the k75s?

Don Ro · 05-01-2004, 10:17 AM

...there, Scott.
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Isn't the K75S one of those Beemers that most people *don't* sell?

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Never ridden one, myself.
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Good luck. (Electrical problems...Ugh!!!)
.

roger albert · 08:51 AM

Looked over the diagram some. I've not seen it myself, but the loadshed relay not grounding through the starter idea seems likely to me. The kill switch wiring, which I originally mentioned, is the same as wire-15 mentioned by someone else, and appears to also be a potential culprit.

It seems to me, that if you had a starter worn bad enough to need brushes, then the the armature must also have been fairly worn. Worn ones arc more, creating more deposits, and causing possibly faulty connections at a quicker rate. Seems like you're looking in the right area. This is just theory and about 20min of wiring diagram reading here. I don't have any real experience nor am I a K expert (and as the day is slowly proving, nor a Triumph expert !@##$%% Back to that now...)

motoyoyo · 05-01-2004, 12:29 PM

Roger, it is a 1988. One possibility that I'll look into is that the brushes and brushplate were replaced, but the armature was not removed and cleaned. This would have left all the old deposits in the motor which might explain why the problem came back after only 2K miles.

Don, yes I would consider the K75S the most desireable of the old K bikes, and can't believe I actually sold it. Thanks for reminding me...