Rotary valve engine

A reciprocating engine comprising:

• an engine body presenting an internal chamber and a fluid intake that supplies intake fluid to the internal chamber;
• a piston that oscillates within the internal chamber during engine operation, said engine body including a head that presents a passage intersecting the internal chamber;
• a head plug adjustably axially positioned at least partly within the passage, with movement of the head plug axially along the passage serving to adjust the compression ratio of the internal chamber;
• a spark plug, said head plug presenting a plug opening that removably receives the spark plug, said piston presenting a side surface and an upper combustion surface, said upper combustion surface defining a piston concave opening spaced from the side surface, said fluid intake defining an inner intake port adjacent to and fluidly communicating with the internal chamber to permit fluid flow into the internal chamber;
• and a rotary valve assembly fluidly disposed along the fluid intake to control the inner intake port so as to generally block fluid flow to the internal chamber when closed and permit fluid flow to the internal chamber when open, said rotary valve assembly including a rotatable cylindrical valve body operable to intermittently block fluid flow through the inner intake port and thereby close the rotary valve assembly as the rotatable cylindrical valve body rotates, said piston presenting a concave end surface that is adjacent to and extends alongside the rotatable cylindrical valve body when the piston is located at top dead center.