Abstract: A two or four stroke valve engine including at least one cylinder (3) within which a piston (4) moves and which receives an air-fuel mixture via at least one induction or intake duct (16). For the combustion products, at least one exhaust duct (17) is operationally connected to the cylinder. The intake duct (16) and the exhaust duct (17) each are provided with at least one respective valve member (18, 19) subjected to an operator device (25, 26) to open it during the use of the engine, and a closure device (28) retuning the valve member (18, 19) into the position in which it closes the respective duct (16, 17). The valve members (18, 19) are positioned to the side of the cylinder (3) and intercept apertures (16A, 17A) of the respective ducts (16, 17), which open into at least one mixing chamber (13) positioned to the side of the cylinder (3) and communicating with it. At least in correspondence with the chamber (13), an ignition device (8) for the mixture present in it is provided.