Rotary valve internal combustion engine

A rotary valve internal combustion engine adapted for use in a hand-held machine, comprising:

• a piston connected to a crankshaft and being reciprocatable in a cylinder, the cylinder having a combustion end,
• a combustion chamber being defined in part by the piston and the combustion end of the cylinder,
• a valve housing being fixed at an outer portion of the combustion end of the cylinder and defining a bore,
• a rotary valve rotatable about a rotary valve axis in the bore, the rotary valve having a hollow valve body having an interior volume forming a part of the combustion chamber, wherein the interior volume of the hollow valve body is subjected to combustion gases throughout the combustion process,
• in a wall part of the rotary valve, a port giving, during rotation of the rotary valve, fluid communication successively to and from the combustion chamber via inlet and exhaust ports in the valve housing,
• a carburetor for controlling the air/fuel mix into the combustion chamber,
• an exhaust muffler for exhausting exhaust gases from the combustion chamber,
• wherein the inlet and exhaust ports are arranged such that a main body of the carburetor and a main body of the exhaust muffler are on opposite sides of the engine and substantially parallel to a centerline of the crankshaft,
• wherein, when the piston is at top dead center, the inlet port is angled by a first predetermined number of degrees towards the carburetor to reduce a radial offset of the inlet port, thereby causing a mounting flange for the carburetor to be substantially parallel to the centerline of the engine,
• wherein the centerline of the inlet port is offset, by a first angular offset, towards the carburetor by a second predetermined number of degrees from a radial line from the cylinder axis, the first angular offset allowing the mounting flange for the carburetor to be substantially parallel to the centerline of the engine, and
• wherein the centerline of the exhaust port is offset, by a second angular offset, towards the exhaust muffler by a third predetermined number of degrees from the radial line from the cylinder axis, the second angular offset allowing the main body of the exhaust muffler to be substantially parallel to the centerline of the engine using an angled mounting flange.