Hi Guys,
Problem:
front brake lever can be pulled almost all the way through without effect on a BMW r1200gs, year 2011 with ABS.
Luckily not while riding through the mountains (where I guessed the problem came from) or speeding on straight roads, only when parking it with the engine still running, or in the morning after starting it.
So today I finally changed the brake fluid the conventional way, the only way I know: 1. valve at break lever, 2. left brake valve, 3. right valve, 4. valve at brake lever again. From the left brake air came through the tube while pumping. Then I pushed the bike 3 meter to park it but same happened: lever pulled almost all the way through again, but now even with the engine off.
The second grip on the brake is always successful.
Back wheel brake always worked.
Actually not sure if there is a real connection of engine on/off and the problem or it was just by chance first with engine on, then with engine off.

Running one more time brake fluid through the system?
Cleaning the brake cylinders for better movement, because they might not move back?
I dont know jet how the three brakes are connected, so if there might be a "central problem".

For any suggestions I will be very thankful,
cheers,
Thomas