In a two-
stroke reciprocating
piston engine having at least one cylinder (1) whose
combustion chamber (3) has an outlet opening (4), which can be controlled by an outlet valve (5) which can be actuated by means of an actuating device which comprises a feed device and a return device, and on whose
cylinder head (2) is placed a valve housing (9) which comprises an outlet duct (8), which adjoins the outlet opening (4) of the
combustion chamber (3), and a guide sleeve (10), which engages through the upper wall of said valve housing (9), for a shank (7), which extends through the outlet duct (8), of the outlet valve (5), wherein the return device has a
piston (15), which is attached to the valve shank (7), and a
working space (17) which is delimited by said
piston (15), is acted on with
compressed air and is sealed off from an annular gap (11),; which is present between the mutually facing guide faces of the guide sleeve (10) and valve shank (7), communicates with the outlet duct (8) and can be supplied with oil, by a sealing device which is arranged in the region of the upper, outlet-duct-remote end of the annular gap (11) and has at least one sealing ring (22), according to the invention, it is possible to provide a simple design and a service-free mode of operation in that, above the sealing ring (22), which faces towards the outlet duct (8), of the sealing device, an oil reservoir (24 and 31 and 36) is provided which can be filled with oil and is filled with oil at the upper side, which faces away from the outlet duct (8), of said sealing ring (22).