From new my CB750F1 brake lever came way back, despite lots of bleeding it did not improve, so I cut a slice from a piece of steel rod and made a spacer, this took up the slack. Over the years the pads have been changed, the fluid changed, the seal/piston changed, the master cylinder changed, the brake lines changed to braided, but the spacer is still in there. It does not improve braking but it feels nicer.
Cheers
Den