My '04 660, which we bought new and just use as a golf cart around the yard started having rear caliper issues. The caliper wasn't releasing and it wore the brake pads down to bare metal and then got where it had tremendous resistance to even rolling. I took the caliper off and screwed the piston in just as the internet said and replaced the pads. Very shortly it did the same thing again. I assumed the caliper was sticking and bought a Chinese replacement from e bay. I stupidly chunked the original Yamaha part when putting the replacement on. Now after very little use the other one was sticking to the point that it again wore the pads out. I doubt that it's been 5 miles back and forth to the mailbox with the new caliper. The brake pedal went away and it was hemorrhaging fluid out of the emergency brake arm. So I pulled the caliper today and there is a little o ring hanging half out around a shaft inside where the emergency brake assembly bolts on with the two allen bolts. The piston is again extremely extended and the shaft for the emergency brake activation is down flush with the part of the casting it sits in and that's probably what caused the failure. So the question is, WHY did the original Yamaha caliper start sticking (no leaks) and what caused the el cheapo replacement to do the same? I hate to start throwing parts at it, but am thinking of buying a master cylinder and the rubber hoses. I have had a rubber hose colapse internally on one of my old Corvettes that caused issues with brakes not releasing on one wheel.