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post #1 of 10 (permalink) Old Jun 24th, 2009, 10:00 pm Thread Starter
 
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Starter runs by itself

I have a 1984 RS 100 K in which the starter motor runs by itself intermittently regardless of what position the ignition is on. I have replaced the starter relay at the advice of a BMW dealer mechanic but the problem is still there. When it happens, which is becoming almost all the time, the only way to stop it is to disconnect the battery, of which the wiring and terminals become very hot.

As this is my first BMW, any suggestions would be greatly appreciated, thanks.
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post #2 of 10 (permalink) Old Jun 25th, 2009, 5:23 am
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Unfortunately or fortunately as the case may be it is a well known problem and well documented. Many probable causes but in my case it was bad ignition switch contacts which had to filed rather than just cleaned and in another post higher than normal resistance on the clutch switch.

I ended up putting an auxilliary kill switch in the battery earth circuit, just in case, along with new battery and bigger leads, new starter relay, overhauled starter etc, but in the end a simple case of a bad connection.

Make sure your battery is in good condition as that can contribute or cause the problem as well.

Regards,

Phil

Phil Mars

1984 K100RT
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post #3 of 10 (permalink) Old Jun 25th, 2009, 9:39 am
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Lazarus
Here is a great link to all things first generation "K"! http://www.ibmwr.org/ktech.shtml Your problem is detailed at least twice.

Bruce C
'04 K1200RS Capri Blue(totaled)
2008 Triumph Sprint ST
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post #4 of 10 (permalink) Old Jun 28th, 2009, 7:34 pm Thread Starter
 
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Thanks, (especially for the link), it was the starter relay due to a weak battery. Replced the battery and the starter's working fine. Thanks again for your suggestions.
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post #5 of 10 (permalink) Old Jul 4th, 2009, 4:15 am
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Quote:
Originally Posted by phil_mars
Unfortunately or fortunately as the case may be it is a well known problem and well documented. Many probable causes but in my case it was bad ignition switch contacts which had to filed rather than just cleaned and in another post higher than normal resistance on the clutch switch.

I ended up putting an auxilliary kill switch in the battery earth circuit, just in case, along with new battery and bigger leads, new starter relay, overhauled starter etc, but in the end a simple case of a bad connection.

Make sure your battery is in good condition as that can contribute or cause the problem as well.

Regards,

Phil
Hope your 'auxiliary kill switch' was a big one like this. The starter takes a few hundred amps!



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post #6 of 10 (permalink) Old Jul 5th, 2009, 12:30 am
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Hi voxmagna and that is identical to the kill switch I used but I think you will find the starter is only rated at about 600 watts which translates to 50 amps hence the 75 amp starter relay, and making the 100 amp kill switch more than adequate.

Regards,

Phil

Phil Mars

1984 K100RT
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post #7 of 10 (permalink) Old Jul 5th, 2009, 3:17 am
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Hi, I would have expected a lot more from a starter starting a cold engine and we know the oem relay is marginal, since it can get its contacts welded with low charge batteries. I was just curious because some reading your post might have the idea any old switch would be ok.

I've used those switches before on boats and they save unhooking battery cables when you want to hang on a charger, also as an immobiliser/ long stay drain reducer it keeps the would be thief thinking as they'd have to rip off the seat. Pain having to reset the clock though.

Did you find space in the battery compartment or use the toolbox, is there room across the top of the battery to use a copper link to its terminal, got a photo?

The only thing that put me off using that type of battery isolator switch is the exposed terminal bolts. A house breaker switch can do 100A and that has shrouded screw clamps for the wires, linking the 2 poles will push up the current rating . It's rectangular and might find a better space.

Regards - Vox.



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Last edited by voxmagna; Jul 5th, 2009 at 3:23 am.
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post #8 of 10 (permalink) Old Jul 6th, 2009, 5:17 am
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Hi Vox, and fair comment and you would have to wonder how well the standard earth lead would hold up to extended high current, so I upgraded that as well.

Good point about avoiding battery drain and fortunately my bike is an RT so the switch lives in the LH fairing pocket. If I had half a brain I would have put it in the right one but I thought about it after. Also adds an extra level of security as a crude immobiliser.


Regards,

Phil
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Phil Mars

1984 K100RT
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post #9 of 10 (permalink) Old Jul 6th, 2009, 1:05 pm
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Now that really is a proper job.

Reminds me of our buses that have an engine emergency stop switch well signed at the rear - the kids used to run out and throw the switch at stop signals!

I have a feeling the red 'Turn key' can be removed off the shaft by taking out the pin. Then you can keep it in your pocket - even more immobilised!

Ufortunately my RS is pretty much stuck for room and I wouldn't want to fix anything to the fairing as it seems to come off a lot for most work I have to do.



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post #10 of 10 (permalink) Old Jul 8th, 2009, 4:53 am
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Thanks Vox and as mentioned as it is an RT so you are a bit more spoilt for room, and the key on mine has no pin so perhaps a bit too easy to remove.

I was even considering removing the relay and putting in a high current push type starter switch from the '50's era but logic? prevailed.

It does the job though there must be a smaller and neater way to do it but I will let sleeping dogs lie

Regards,

Phil

Phil Mars

1984 K100RT
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