It all started when I replaced the rear brake pads on my 07 ST1300. The rear brakes were sticking, so I took them off two times and while putting the rear caliper back on I noticed the Bolt that the caliper slides on was stripped out. So I found a good used rear caliper on ebay that was close to me so I received it fast. Got it today and switched the caliper and bleed the whole system. Yes it's a pita. When done everything was fine, even took for a short ride. So I think the rear old caliper was bad because before I put the ebay one on I pushed the pistons in and they went in easy not like the old caliper they were hard to push back in. So now very happy again.