On the Fichtel Sachs fork you can remove the lower legs without removing the fork tubes from the triple clamps. Remove the brake calipers ( wrap them in rags and bungee them away from the fender ) remove the wheel and front fender. If you look at the bottom of the fork slider you will see a 6 mm allen screw recessed into the slider above the axle. There is an opening in the bottom of the leg to allow you to use a long allen wrench to unscrew this screw. It will probably require an impact wrench to break the torque on it. Drain the fork oil before removing this screw, but removing this screw allows the fork slider to be removed from the fork leg. The screw holds the slider to the damper rod. Once the slider is in your hands, work a big flat screwdriver blade under the seal and gently twist the blade to work the seal loose. Once the seal is out, thoroughly clean out the slider with solvent.
To install a new seal I use the BMW seal driver. Otherwise, you could place the seal in the end of the slider and lay a flat piece of wood over it then try to gently tap it into the hole with out getting it cocked sideways or damaging the seal lip. Oh yeah, really important, you must sand the damage to the fork leg that caused the original seal to fail. Some little sharp edge from a nick in the fork leg damaged the seal and caused that leak. What I do is use a strip of 400 grit silicon carbide paper to sand the front and back surfaces of the leg in a cross hatched pattern, rubbing the paper across the leg at an angle in a manner like you would use a rag to shine the toe of your dress shoes. If you don't do this you will immediately damage the new seal.
Put plenty of white lithium grease on the new seal when you slide it back up the fork tube so you don't damage the seal on installation.
This is an article posted by the mason some time ago.
Ajays