Since December 1980 a sealed type master cylinder was gradually introduced, which is impossible to dismantle because the end circlip does not have eyes to remove, and is not marked externally. Start by emptying the master cylinder and the reservoir and getting rid of the fluid. The step to follow is to take the reservoir out of the master cylinder, take off the stop screw and then take out the circlip out of the mouth of the bore. Take out the piston pushrod assembly, the secondary piston assembly and the loose spring. Check the bore wear, damage, and corrosion, when in good condition can reuse with service kit, new cylinder assembly required otherwise. Clean all metal, as required, with methylated spirit, and do not use petrol or other equivalent solvents and leave to dry or use clean lint-free cloth. Take the seals and all the components in the repair kit and moisten them with brake fluid and then install. Make sure that you get the right repair kit since there are two: the ATE and the FAG. Install the secondary piston assembly by installing the two piston seals in the larger diameter end with the lips of the both lips turned away and then install the cup washer, primary cup with its lip towards the closed end, support ring, and conical spring. When the master cylinder body is held at right angles (the open end downwards), it is important to insert the secondary piston assembly carefully into the cylinder and the lips of the seal are forced into the bore. Install the cup washer, primary cup, support ring, cylindrical spring, stop sleeve and stroke limiting screw into the short end of the primary piston and screw the screw firmly into place. Fit to the longer end, metal washer, secondary cup, lip towards the washer, plastic washer, secondary cup, lip towards same direction and lastly, second metal washer. Install the primary piston assembly by firstly attaching the spring end first then the stop screw and sliding the piston in as required to be fully inserted in the cylinder bore. Once the stop screw is in place, insert the circlip at the mouth of the cylinder bore, a new cover on the end of the master cylinder, lubricate the seals with brake fluid and press the reservoir into the seals.