To dismantle the ADR engine, begin by removing the covers on the top of the engine in case they are required. Unscrew the clips and remove the air inlet duct between air cleaner and throttle housing. Unscrew the nut and disconnect the earth cable, disconnect the wiring of the ignition coil at the upper rear of the engine. Unscrew the mounting bolts, detach the HT leads on the spark plugs and take away the ignition coil. Unscrew the mounting nuts step by step to remove the camshaft cover of the cylinder head, and the main and central gaskets of the cylinder head and the oil deflector of the camshaft cover. To refit, wipe the cover of the camshaft and the cylinder head, install the new gaskets, and refix the oil deflector. Install the camshaft cover on the studs of the cylinder head and screw in the nuts to the recommended amount of torque. Install the ignition coil once again, attach the HT leads to the spark plugs, re-connect the earth cable and ignition coil wiring and re-connect the air inlet duct, tightening the clips and, as needed, replace the engine covers. In non-ADR engines, pop the clips, and unscrew the nut to remove the upper timing cover followed by the unscrewing of the nuts to remove the timing belt rear upper cover. Unscrew the rest of the camshaft cover nuts, noting the straps holding the wire and positions of earth terminals, and loosen the reinforcement strips and remove the camshaft cover. UNscrew the oil deflector and gasket of the cylinder head studs and the semi-circular gasket of the front bearing cap of the camshaft and remove the rubber plug of the back of the cylinder head. To refit, clean the camshaft cover and cylinder head surfaces, lay the rubber plug and semi-circular gasket on, lay a new gasket over the studs on the cylinder head, and re-fit the oil deflector. Install the camshaft cover and reinforcement strips, and then install the timing belt rear upper cover, valve cover nuts, and tighten successively to the recommended torque. Lastly, install the upper timing cover, screw the nut and press the clips.