I´ve bought my motorbike 1.5 months ago. after 3-4 days the ABS signals begin to lightning unsynchronized. I went to the service and they said "we have to change ABS center" but the cost is nearly 1.650 Euro in Turkey. Some of my friends which they have 1150 GS; this problem can related with battery. After that i´ve tried with a new battery and than the ABS signals get synchronized ligtning. But when i use the brakes, front break was OK but rear break tapped on drum very powerfull. So i need assistance to find real problem.