R100 GS - Battery light flashing

[chlowden]

Hello
I have a R100 GS and i am struggling with the dashboard battery light that flashes red and it seems to flash at same rate as the revs. I have changed the alternator brushes and done my best with old connectors. I have a good voltage from and to the battery. When riding, I feel that there are "holes" in the combustion but there the bike idles fine.
Lastly, the flashing red battery light turn off when I turn on the headlight. The indicators do not affect the the flashing red lamp, just when I turn on the headlight.
Any ideas are most welcome
Thank you

[Warin]

There are lots of possible causes! You'll need to do some (probably lots) detective work.

When does it occur?
If the bike is stopped and you simply rev the motor?
On smooth bits of road or on bumpy bits of road?
Only when the motor is hot? Both when the motor is cold or hot?

Please list all the conditions when it occurs .. and when it does not..

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Where are you, and where are you headed? There may be locals who could help?

[chlowden]

Thank you for your reply

It happens on flat and off road. It seems to be worse when it is cold and humid but there is no rhyme or reason to this.
What makes my bike strange is that the R100GS motor is mounted on R90S frame and I have 2 coils instead of the standard electronic coil. I am to be getting a decent spark from both but I don't know how to check if the 2 are synchronised or delivering everytime.
This morning, whilst riding, the light flashed very fast but when I rev up at a standstill the light flashed less. I find this strange.
The light flashes be it hot or cold. That said, it is about 4 degrees celcius at the moment, so does the bike ever get very hot.

The condition persists all the time but it is not constant in its intensity. There is an intermittence but it is constantly present.

[chlowden]

I have also noticed that when switch to Hi-beam without the front light on, the flashing also disappears, but one of the other buttons that I push effect the flashing. Lastly, when the bike idles too low to charge, the battery light comes on intermittently when I have the front light on which is normal.

[Two wheels good]

Very puzzling! I've no easy solution just a few ideas.
I'm going to disregard the coil and ignition "holes" as the source of the problem. (This could be a sticky bean-can or even dirty carb jets.)

For the CHG light problem I'm inclined to think of the alternator rotor, slip rings, brushes.
AFAIK the rotor usually fails terminally not intermittently. The CHG light and rotor are in series. So an open cct rotor means no CHG light when ignition is on.

Did you have the problem before changing the brushes?
Switching ign on\off - and engine stopped - is the CHG light behaving itself?
With ign on wiggle some wires and connectors (gently ) to see if the CHG light goes out.

Check connections again - earth connections at gbox and under tank.
Check under the front cover that no wires are pinched or frayed.

You'll find some test routines for the charging system components - regulator, diode board, rotor - online. PM me if necessary. I should have a copy somewhere

Are you reading a consistent 14V or more at the battery terminals when the engine's at 3000rpm? Or does it flicker in time with flashing IGN light

[Warin]

.. Still many possibilities!

When you turn on the hi beam .. as well as the alternator light stopping flashing does the 'ignition hole' stop?

Thinking this could be a bad connection to the battery .. or just a bad battery!

If the battery becomes disconnected .. then the alternator will light the alternator light (as there is no battery voltage on the ignition switch side) .

Where could the battery get disconnected?
Earth cable to gearbox
Any of the battery terminals
inside the battery .. (hit the top and see if that 'fixes' it for a while)

The extra load of the headlight 'fuses' the bad connection .. like a weak spot wield.

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Like I say .. there are a lot of possibilities. Very puzzling. I've no ideas of who to test this .. yet.

[chlowden]

Lots of things to check. Thank you so much for your thoughts, I am going to check it now.