99 WR400, a while ago my rear brake started to not want to release properly, resulting in a wheel that turned but not easily. I took it to the local yamy shop here (were talking Peru) and the head mechanic took the caliper apart and cleaned it all up, put it all back together and it's doing the same damn thing as before. I mean supposedly the pistons were (still are?) dirty, and were not moving back when the pressure was off. Is it possible that those pistons are fine and the problem is that I have been using dot 3 fluid and it's expanding as things heat up??? Please explain.... I guess I should immediately google something on the order of "expanding brake fluid problem". Tanx velly much.