Hi! BMW K1100LT with the ABS II unit.

I've been having a problem with my ABS for a while now, and was wondering if there's a simple fix available.

When I start up my bike, the ABS works perfectly. It calibrates itself correctly, and works as expected. After some time, when it re-calibrates itself at a stoplight, it does so correctly as well.

But, after roughly 30-45 minutes of riding, whenever it tries to re-calibrate itself, it immediately shows a fault. a LED blinks 7 times, so apparently it's reporting there's some error in the brain. No matter how many times I clear the ABS fault, the moment I pull away it reports a fault immediately.

Only when I stop and let the bike cool down for 10-15 minutes, the ABS starts working correctly again, before showing the fault again after a few (or few-teen ) minutes.

Also, this is mostly independent on the engine temperature. I can start the bike and let it sit until the cooling fan turns on, and the ABS will calibrate and work. Alternatively, even if I move at a constant speed, cooling the bike, it still shows the fault after 30-45 minutes if I ever stop and go again.

Thanks in advance for any help!

ABS units require good batteries. The first things you should do is check your battery connections, the battery itself and the charging system.
Regards Martin.

MartinW wrote:ABS units require good batteries. The first things you should do is check your battery connections, the battery itself and the charging system.
Regards Martin.

I have a voltmeter attached to the bike. Sometimes when I start it cold the voltage drop from the starter makes the ABS fault instantly, but turning the ignition off and on clears that kind of fault, so I let the bike warm up for a bit, do that, and it works from then on.

Once the engine is running I always have above 13 volts, and when the RPM's go above roughly 1100, it hits 14.

EDIT: Also, whenever I know the abs will want to calibrate, I rev the engine to ~3k rpm so it has all the alternator power it could need.

Alternator looks to be good. Get your battery checked if it's not up to specification it can still mess with the ABS. A good battery is critical to a functional ABS.
Regards Martin.