R100 Gs Electrical Problem

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R100 Gs Electrical Problem

Postby Jsampso3 » Mon Apr 02, 2012 6:38 pm

I have a 1991 BMW R100 GS. I took it out the other day and rode it for an hour. Came home and parked for 30 minutes and when I went to start it I got a high pitched buzzing sound and the RPM gauge slowly rises. Any ideas??

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Re: R100 Gs Electrical Problem

Postby Lolo » Mon Apr 02, 2012 7:27 pm

Hi and welcome to the forum :smile:

Thats an interesting problem you have there :-k
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Re: R100 Gs Electrical Problem

Postby Jsampso3 » Mon Apr 02, 2012 7:45 pm

Thank you! I am absolutely stumped..The battery can be fully charged and it has no impact..Could it be coil?

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Re: R100 Gs Electrical Problem

Postby Galactic Greyhound » Tue Apr 03, 2012 11:35 am

Hi and welcome to the forum!

The high-pitched buzzing sound may be coming from the Starter Relay trying to operate with a low battery voltage or a failed battery. This can sometimes cause the Starter Relay contact to weld together (you will know if this has happened because the Starter Motor will run at Ignition 'On' without pressing the Start button).

The best way of determining if it is a battery problem is to remove your suspect battery and substitute/jumper a known good battery (you can use a 12v car battery) in place of the existing battery and see if things work OK. WARNINGS: Do NOT connect the substitute battery across your suspect battery in case this is faulty or a big bang might result! Do NOT disconnect the substitute battery when your engine is running or the high alternator voltage may fry your electronics!

If it works with a good substitute battery then try re-charging the existing battery. Bear in mind the existing battery may be flat because your charging circuit has failed or you left something switched on. Also, a battery can show 12 volts but be unable to deliver the high starting current (around 200 amps) because it has aged. This will cause the voltage to drop dramatically when the starter is operated.

Here is a Word document which may be useful:
R100 Not Starting..doc
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