Author Topic: 1985 K100 won't start and the lights don't come on  (Read 12636 times)

Offline jak212

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1985 K100 won't start and the lights don't come on
« on: May 08, 2017, 09:17:24 PM »
I've been reading through a lot of the posts about bikes that don't start and I feel comfortable posting because I think I have a unique situation. I'll start with the problem for those of you that don't care about that back story and then circle back around to it.
With a brand new battery, the dash clock worked just fine. When the key turns on, the clock goes away, the headlight does not come on, the turn signals don't work, the horn doesn't work, there is no green neutral light, and needles to say, when the starter button is pressed, nothing happens. I can't remember if the tail lights or brake lights work. I don't think we tested that.
Anyways, the problem started when I came back from a vacation and found that my roommate had taken the battery tender off the bike and moved it to a different corner of the garage.
Figuring that the battery was dead, I tried jumping it with my car.
At this point the lights came on when I turned the key and everything seemed normal. But after I hit the starter button, the lights turned off and everything else stopped working. There was an audible click when I pressed the button. I still have no idea what that could have been. I double checked all of the things that got me before, like the kill switch, but it was in the middle and on. I tried in in up, middle, and down though just for good measure. As mentioned before, the battery is brand new. I have also replaced the starter. The relay clicked when I had a friend who is actually good with electricity help me out. The points aren't corroded either.
My theory is that the ground wire in the wiring harness running from the relay to the handlebars is bad and nothing up there is getting any power. I suppose it could be the ignition module too, but thats an expensive fix and I don't think that would affect the lights and switches in the handlebar/dash assembly.
If anybody knows what that wire harness is called and where to find one, I would appreciate it. Or if you think I am dead wrong and have other ideas, I am all ears. I am a decent mechanic, but a lousy electrician so I can use all the help I can get.
  • Southern California
  • 1985 BMW K100

Offline Laitch

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Re: 1985 K100 won't start and the lights don't come on
« Reply #1 on: May 08, 2017, 09:32:47 PM »
I've been reading through a lot of the posts about bikes that don't start and I feel comfortable posting because I think I have a unique situation.
Your situation isn't unique. It's  typical of old K-bikes, especially those with discharged batteries, dirty starters and/or bad relays fouled by attempts at starting the bike with insufficient current.

First. fully charge the battery until its over 12.7V. +13V would be nice. then try it again. If that doesn't work try backspin starter No-Start technique #1 . You can read about it in the very section you have posted this non-unique problem.

Report back with the results.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline jak212

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  • Posts: 4
Re: 1985 K100 won't start and the lights don't come on
« Reply #2 on: May 08, 2017, 10:21:33 PM »
The battery was brand new and was charged by the shop. When that didn't do the trick, I pulled it and put it on a tender and ordered a new starter and installed it. That didn't work either. I can check the voltage on the battery and verify that its healthy and I can backspin a brand new starter but that doesn't seem productive. Neither of those options would explain the total absence of lights or lack of any response from the switches switches. There is no fuel pump noise, the starter doesn't engage at all, and the lights aren't dim, they are out.
  • Southern California
  • 1985 BMW K100

Offline Elipten

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Re: 1985 K100 won't start and the lights don't come on
« Reply #3 on: May 08, 2017, 10:31:57 PM »
You have asked for help from the members here.  None are there to assist.  The only solution to this problem is a methodical step by step series of tests and data collection with reporting the results.

So check and verify.  Measure the voltage and report back.  Who says the battery is charged?  The shop?

Check the voltage and report back.


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  • San Antonio, TX
  • 1990 K75RT

Offline jak212

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Re: 1985 K100 won't start and the lights don't come on
« Reply #4 on: May 08, 2017, 10:34:07 PM »
You're right. I'm sorry. I'm just frustrated by the whole situation.
  • Southern California
  • 1985 BMW K100

Offline thecableguy

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  • Posts: 115
Re: 1985 K100 won't start and the lights don't come on
« Reply #5 on: May 08, 2017, 10:40:40 PM »
Search this site for instructions on cleaning your ignition switch.  Intermittent contacts there will cause all sorts of electrical gremlins.


Jim
  • Madison, WI USA
  • 86 K100RT - Brünhild
...to make a long story short, use duct tape.

Offline Elipten

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Re: 1985 K100 won't start and the lights don't come on
« Reply #6 on: May 08, 2017, 10:52:55 PM »
Frustration is understandable.  You have the most experienced set of knowledgeable Kbike minds available on this site.  And in my experience they will work the toughest problem to the end with you if you ask nicely.  It is a crusty group at times.

Do each step, report back, read the threads on the site and I will bet in a few days or weeks your bike will be running.

Now you could have something new, that has never been seen but there is only one path to resolve the issue.

Logical, methodical work.

Best of luck, I am sure the inmates will help, just don't bite them

Oh yes, most of these problems are not solved by throwing money and parts at it.

Get a couple of cans of Deoxit.  You need to clean each electrical connection.

Clean the negative battery cable at the frame.


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  • San Antonio, TX
  • 1990 K75RT

Offline The Mighty Gryphon

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Re: 1985 K100 won't start and the lights don't come on
« Reply #7 on: May 09, 2017, 01:51:06 AM »
Given the vintage of your bike, the first things I would do while the battery is charging is clean the ignition switch and all the ground connections.  A couple years ago I had a very similar problem that was caused by the ignition switch.  Cleaned it and, knock on wood, it's been working fine since.  Any time you have widespread goofy electrical problems the usual cause is a bad ground somewhere.  First thing when troubleshooting electrical problems is to clean and tighten all the grounds.

Cleaning ignition switch:  http://www.eilenberger.net/K75S/IgnitionSwitch/

If you don't already have some, get a can of DeOxit electrical contact cleaner.  That is probably the most important thing the owner of an old brick can have in the tool box.  Avoid cleaning electrical things with anything abrasive.  That will just remove more plating, and increase the rate of corrosion. 

Another thing to consider is that some battery maintainers don't have enough output to charge a dead battery in less than 2-3 days.  If there is something in your electrical system that discharged a new battery while the bike was parked, the current draw will make it take even longer to get the battery up to a full charge.
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline Elipten

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Re: 1985 K100 won't start and the lights don't come on
« Reply #8 on: May 09, 2017, 07:38:23 AM »
Yep a battery maintainer is not typically a high output battery charger.  A couple of amps output will take forever to charge a battery


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  • San Antonio, TX
  • 1990 K75RT

Offline Motorhobo

  • +25 years of K75
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Re: 1985 K100 won't start and the lights don't come on
« Reply #9 on: May 09, 2017, 09:17:24 AM »
Two comments --

1) sufficient voltage doesn't guarantee sufficient starting power (cold cranking amps) -- I've had batteries come off the charger reading +12V but had no amperage to speak of -- the only way to be sure a battery is still good is to have it tested for CCA -- but I think that's not relevant here as you battery sounds to be fine

2) I had what you appear to have more than once and the first thing I do these days is pull the plug on the ignition control unit, spray a bit of electrical contact cleaner (if available) on the contacts and plug it back in. I'd do that first if you haven't done it already then proceed to cleaning the rest of the contacts on the bike. The reason I'd do that first is that it's a prime culprit for this kind of behavior.

My $0.02...



1994/1995 K75 ABS Frankenbike: original engine 136k miles, frame from Gary Weaver (RIP), 173k miles -- Current Odometer: 198k miles
1994 K75 since 2013, 82,000 mi (19k mine) w/California Sidecar Friendship II Sidecar & Black Lab 'Miss B' - RIP

Past: 1974 Honda 550/4 (first bike), 1994 K75 (sold), 1995 K75 ABS (parts bike), Sidecar Dog & Best Bud 'Bo' - RIP

Offline Laitch

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Re: 1985 K100 won't start and the lights don't come on
« Reply #10 on: May 09, 2017, 10:20:50 AM »
My $0.02...
Experienced German language translators have had their $0.02 bumped up to $0.03.  I read it somewhere.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline The Mighty Gryphon

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Re: 1985 K100 won't start and the lights don't come on
« Reply #11 on: May 09, 2017, 10:36:46 AM »
$0.02  what is that in dm?
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline jak212

  • Curious
  • Posts: 4
Re: 1985 K100 won't start and the lights don't come on
« Reply #12 on: May 11, 2017, 07:12:20 PM »
First of all, sorry for the rocky start and thank you all for the advice.


Progress from this week:
I took the battery back to the shop and had them test it. The volts were down to 21.4v so I had them top it off to 12.7v+. It putting out plenty of amps as well. I plugged it back into the bike and I tried the No Start technique of rolling back in third and popping the clutch. Sadly, no results.


Plan moving forward:
As soon as I can get some DeoxIt I will spray out the Ignition Control Unit, clean the Ignition Switch, and clean the rest of the contacts as well. I have found a couple different brands of the spray and I'm curious if it matters what brand I buy.


Plan B:
In the event that I let the magic smoke out of the brain box and fried the wiring harness during the car-to-bike jump, I did some research and found both on line. An OEM Ignition Control Unit is $1,200 before tax and shipping so that is clearly not my first choice. The Chassis Wiring Harness OEM is over $500 so that isn't great either. There are some options on eBay that are far and away less expensive, but I am reluctant to spend money on second-hand electronics. Do any of you know of any after market options for K bike electronics? I am in high desert north of LA for anybody that knows a good parts supplier. I hope cleaning everything will cure my woes but I wan't to have a back-up plan just in-case.


Thanks again!
  • Southern California
  • 1985 BMW K100

Offline Filmcamera

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Re: 1985 K100 won't start and the lights don't come on
« Reply #13 on: May 11, 2017, 08:16:15 PM »
Second hand electronics from a reliable source like Beemerboneyard I would consider OK.  Ditto anything from Ebay from a seller with a good rep who warrants the part working when you purchase it, that way you have bay protection in case of any issues.


My loom was a disaster so I rolled the dice and brought one from ebay and it was great, though as the saying goes YEMV.
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2022 Triumph Tiger 900 Rally Pro
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Offline rbm

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Re: 1985 K100 won't start and the lights don't come on
« Reply #14 on: May 13, 2017, 08:49:23 PM »
So, are you aware of the K100/K75 Troubleshooting page from the K100 forum?  If not, open the link to see the excellent information there, including a flowchart to isolate problem components on the bike.


I have colour schematic diagrams available for your model bike.  Download it from my Google Drive.  These schematics makes it easier to trace the schematic and match the wiring in the harness.


If you have a good battery (which you allege) but you don't get any lights with the ignition switch in the "Park" or "ON" positions and the kill switch centred, then you have a problem with getting current to the start circuitry.  The first stop for current is the ignition switch and should be you first component to investigate. 


1. With the ignition switch in "Park", you should be measuring +12V at Fuse #2 with the ignition switch either in "Park" or in "On" positions.  If you don't get this reading, the problem is your ignition switch.  y

2. With the ignition switch in "On", you should measure +12V at Pin 86 (Green) on the load shed relay in the relay box. If you don't get this reading, the problem is your ignition switch.

3. Another check is to see if you have power at the Red wire on the start relay and the Red wire on the FI relay, both in the relay box.  If you do, that means the basic wiring for starting is available.  Continue to f ollow Bert's flowchart above to conduct the appropriate tests.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline Holstson

  • Motobrick Curious
  • Posts: 11
Re: 1985 K100 won't start and the lights don't come on
« Reply #15 on: June 28, 2017, 06:31:26 PM »
First of all, sorry for the rocky start and thank you all for the advice.


Progress from this week:
I took the battery back to the shop and had them test it. The volts were down to 21.4v so I had them top it off to 12.7v+. It putting out plenty of amps as well. I plugged it back into the bike and I tried the No Start technique of rolling back in third and popping the clutch. Sadly, no results.


Plan moving forward:
As soon as I can get some DeoxIt I will spray out the Ignition Control Unit, clean the Ignition Switch, and clean the rest of the contacts as well. I have found a couple different brands of the spray and I'm curious if it matters what brand I buy.


Plan B:
In the event that I let the magic smoke out of the brain box and fried the wiring harness during the car-to-bike jump, I did some research and found both on line. An OEM Ignition Control Unit is $1,200 before tax and shipping so that is clearly not my first choice. The Chassis Wiring Harness OEM is over $500 so that isn't great either. There are some options on eBay that are far and away less expensive, but I am reluctant to spend money on second-hand electronics. Do any of you know of any after market options for K bike electronics? I am in high desert north of LA for anybody that knows a good parts supplier. I hope cleaning everything will cure my woes but I wan't to have a back-up plan just in-case.


Thanks again!
Try out : https://www.motorworks.co.uk/vlive/Shop/Parts.php if you in the end need some ignition parts.






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  • Norway, Oslo
  • K75s , R65/6

Offline heatherlake

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Re: 1985 K100 won't start and the lights don't come on
« Reply #16 on: February 27, 2018, 03:23:00 PM »
I have the same problem. Did you solve the problem and how?
  • Denmark
  • k100RS

Offline Laitch

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Re: 1985 K100 won't start and the lights don't come on
« Reply #17 on: February 27, 2018, 03:59:31 PM »
. . . I have the same problem. . . .
Welcome, heatherlake. Start a thread of your own about your bike's problem. Tell us what you've done so far. Post a picture of it. Put the year of its manufacture in your profile because the 1990—1992 K100RS models are different than earlier K100RS models.

jak212 might not post again but you can always send jak a personal message.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

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