You haven't said whether or not you have rebuilt or worked on the master cylinder. If you have, you might want to be sure it is relasing totally. The brake fluid must be able to move between the reservoir and the actual cylinder for the master cylinder to function correctly. I have seen a piece of junk get in the reservoir and plug the hole in the bottom of the reservoir into the cylinder portion of the unit so that the fluid cannot move correctly between the two, causing the master cylinder to build up a small amount of pressure and cause the brakes to drag. Also, if the cylinder was rebuilt, but something was not installed correctly in the rebuild of the cylinder, it may not be functioning correctly causing the same problem. Just a couple of things to check in hopes of helping you to find the problem.
Joe
