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Old Yesterday, 03:53 PM   #1
Ramanonos OP
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Location: Hood River
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Little charge on r100gs unless I rip her

This has been a slow creeper issue on my r100gs. Owned this bike almost a year (love it). Alternator won't post a charge unless I rip the rpms in gear really flipping hard. It used to be fixed this way but now it takes more and more of a rip. After that initial red line thing is over with, I'm good the rest of the ride with multimeter showing 13.2. If I don't red line... 11ish forever. Ok, something is wrong. And my workaround fix isn't helping her. Not only do I have to redline a 2nd gear take off more aggressively, but the steady state volts has gone from 13.9 to now... Barely 12.7.

Shit. I haven't yet learned about the electric system of this bike. I'm hoping I can solder some brushes on the alternator, but maybe not... Maybe something else is to blame? Help.?I'm unsure how to check where or what on the r100gs to see what's wrong. Guidance and pics appreciated
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Old Yesterday, 06:07 PM   #2
hardwaregrrl
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Oh boy....first of all get a voltmeter and put it on the battery. By the way, how old is the battery? Then start the bike and watch what happens as you increase the RPMs. You should be in the 13.9-14.3 volts range around 4200 depending upon what charging system you have. The stock system will not start charging until around 3k. Start there and report back. You next thing to do would be checking the brushes and the rotor. Plenty of threads here on that topic.
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Old Yesterday, 07:41 PM   #3
Warin
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Fundamentals...

When you turn on the ignition .. but before your press the starter you should have two red lights ;
One for oil pressure
One for 'battery' - actually the alternator.

If you don't have the alternator light .. then it may not start charging .. sometimes it it will start charging if you increases the engine speed substantially .. other times not start to charge at all.. it really needs that red light.

-------------------------------------------------
2nd problem .. low charge voltage ... might be the voltage regulator. But check the above first, as that could be your startup problem.
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Old Yesterday, 08:37 PM   #4
Biebs
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Diode board

Red alternator light working is it dim when high rpm??


I get 13.3 volts at 3500 rpm after new diode board and connection cleanup.
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Old Yesterday, 09:59 PM   #5
Mark Manley
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It might be a dirty rotor where the brushes run or worn out brushes, they are worn out when about a third of the original length. Take the front cover off and with the engine ticking over VERY CAREFULLY touch the rotor slip rings with a small piece of wire wool or Scotchbrite to clean them then check brush length, this might help.
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Old Today, 07:21 AM   #6
hardwaregrrl
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I don't recommend you remove the front cover with the engine running. Bad shit could happen. Disconnect the negative battery cable, then remove the cover. Replace cable and start bike. Using a scotch brite pad, touch the rotor rings as they spin if you want to clean them. Brushed should be 7mm long at the minimum.
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Old Today, 10:02 AM   #7
Ramanonos OP
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Battery is new. I've already done the voltmeter check. Taped one on the tank so I could read in gear at different rpm. As I mentioned in my original post, I get up to a normal state charge of 13.9. But not without a big ass kick on the throttle for an extended time. Otherwise I'm not getting past 12.5. Regular riding, I can dip below 12. I wrote this off a quirk, but lately I'm needing to go rev harder and takes longer to get to desired 13.9 steady state. Something's clearly wrong. Just curious if anyone had the same experience: Needing a red-line twist in 2nd or 3rd to get volts up.
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Old Today, 11:36 AM   #8
Solo Lobo
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If you aren't above 13V at 2,500-3,000 rpm there is something wrong.
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Old Today, 03:25 PM   #9
Warin
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Quote:
Originally Posted by Ramanonos View Post
Something's clearly wrong.
Yes, something. And your hoping someone has had exactly the same problem with the same symptoms. The thing is those symptoms match a number of faults .. and your not telling us all the information that you have.

What is the behavior of red battery warning light ?

Does it come on, go off, flicker, dim, come on when the bike is first turned on before the motor is started??????????????????????????

That information will help isolate the problem ....
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Old Today, 03:43 PM   #10
globalt38
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Year of bike would help as well. Difference in the electrics between an 80's R100gs and a 90's
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Old Today, 07:22 PM   #11
Beemerguru
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Year and mileage. Well taken care of or rat bike?

Another possibility is corroded connections..Gas tank off, unplug and No OX to the contacts for the VR, same for the 3 wires on the front of the stator...and if you want to take off the diode board, the 3 wires and blue wire that plug in the back...you can loose over a volt with bad connections...and having to spin the motor way up means something mechanical is not right..start with the brushes and clean the rotor.
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