Moment-cancelling 4-stroke engine

An internal combustion engine comprising a first cylinder having a first piston and a second cylinder having a second piston, a first crankshaft operably connected to the first piston and a second crankshaft operably connected to the second piston, a cylinder head comprising at least one intake port and at least one exhaust port per cylinder, said at least one intake port connected to the first cylinder such that fluid can pass through the at least one intake port into the first cylinder and said at least one exhaust port connected to the first cylinder such that fluid can pass from the first cylinder through the at least one exhaust port, a movable intake valve positioned at least partially within the at least one intake port configured to control the flow of fluid through the intake ports, a movable exhaust valve positioned at least partially within the at least one exhaust port configured to control the flow of fluid through the at least one exhaust port, the at least one intake port having a minimum intake port diameter, a first inside radius positioned toward an intake port valve seat from the minimum intake port diameter, said first inside radius transitioning to a second inside radius positioned toward the intake port valve seat from the first radius so that the intake port expands to meet the intake port valve seat, the first inside radius being greater than 0.4 inches and less than 1.5 inches, the second inside radius being greater than 0.13 inches and less than 0.7 inches, the at least one intake port having a non-symmetric variable shape along at least a portion of a length of the at least one intake port, said movable intake valve defining an intake valve seat angle measured between the surface of the movable intake valve most distal from an intake valve stem of the movable intake valve and a plane perpendicular to the axis of movement of the movable intake valve, said intake valve seat angle being between about 40-52 degrees, said movable intake valve defining an intake valve undercut angle measured between the surface of the movable intake valve adjacent to an intake valve seating surface defined b the intake valve seat angle and positioned radially inward therefrom and a plane perpendicular to the axis of movement of the movable intake valve, said intake valve undercut angle being between about 30-42 degrees, said movable exhaust valve defining an exhaust valve seat angle measured between the surface of the movable exhaust valve most distal from an exhaust valve stem of the moveable exhaust valve and a plane perpendicular to the axis of movement of the movable exhaust valve, said exhaust valve seat angle between about 40-52 degrees, said movable exhaust valve defining_an exhaust valve undercut angle measured between the surface of the movable exhaust valve adjacent to an exhaust valve seating surface defined by the exhaust valve seat angle and positioned radially inward therefrom and a plane perpendicular to the axis of movement of the movable exhaust valve, said exhaust valve undercut angle being between about 30-48 degrees, and an intake port angle of the at least one intake port is between about 45 and 65 degrees, wherein the first crankshaft rotates in a first direction and the second crankshaft rotates in a second direction such that the second direction is an opposite direction from the first direction.