A noise suppression system for an air-cooled internal combustion engine is disclosed. The system may include an acoustically designed shroud forming a cavity and configured for attenuating noise produced by a cooling air fan associated with the engine. In one system, the shroud is mountable on a housing of the air fan. A pair of air inlet passages may be provided which are operable to draw ambient cooling air into the shroud to the fan. The air inlet passages are acoustically configured and tuned to attenuate noise generated by the fan. In one system, the air inlet passages may each be formed in a rear quadrant of the shroud. Various configurations of the shroud may include quarter wave resonators and/or micro-perforated panels to further attenuate fan noise.

A single-cylinder internal combustion engine includes a knock sensor mounted thereto to suppress a temperature increase of the knock sensor and at the same time detect knocking with high accuracy. The engine includes a cylinder block having a cylinder provided therein, and a cylinder head connected to the cylinder block. On a surface of the cylinder block and the cylinder head, one or more fins protruding from the surface are provided. On the surface of the cylinder block, a sensor mounting boss protruding from the surface and being continuous with a portion of the one or more fins is provided. A knock sensor arranged to detect knocking is mounted to the sensor mounting boss.

An air cooled machine is formed with a housing and a plurality of heat rejecting fins with a heat pipe system disposed therein. The heat pipe system includes a primary passageway and a plurality of leg passageways extending through the housing and into each fin. A working fluid is disposed within the heat pipe system and is operable to receive heat from a heat source, change material phase at a threshold temperature and transfer the heat through the fins to a surrounding atmosphere.

An actively cooled air cylinder for a motorcycle engine comprising a cylinder block. The cylinder block may comprise an upper mounting surface, a lower mounding surface, an internal bore extending between the upper mounting surface and the lower mounting surface, a forward facing surface, a rear facing surface, and first and second side surfaces. Each of the surfaces may comprise a plurality of fins and a plurality of cooling channels located between each of the plurality of fins. The cooling channels may comprise a series of peaks and valleys that configured provide turbulent flow of air over the cylinder block when airflow contacts the cylinder.

An apparatus is provided including an insert for an engine. The insert includes an elongated body sized to be positioned in an opening defined in the engine. The elongated body extends along a longitudinal axis from an upper end to a lower end. A fin extends outwardly from the elongated body. A flange extends outwardly from at least one of the fin and the elongated body. A locking mechanism is coupled to the elongated body and is moveable along the longitudinal axis between a first position in which the locking mechanism is positioned in the elongated body and a second position in which the locking mechanism extends outwardly from the lower end of the elongated body.

A general purpose engine with a cleaning access window defined therein is in the form of an air cooled engine, having a cylinder unit made up of a cylinder and a cylinder head, and includes a housing for covering at least the cylinder unit and a cleaner covering removably fitted to the housing for covering the filter section of the air cleaner, the housing being formed with a blow window so as to confront gaps between a plurality of cooling fins provided in the cylinder unit, and the cleaner covering has a closing section defined therein for covering the blow window.

A cylinder cooling system for aircraft engines is disclosed in which an air intake leads to multiple air chambers and the air is divided among the air chambers, which lead to the cylinders of the engine. In this way, approximately equal amounts of air of approximately the same temperature are able to pass over each cylinder, thereby providing more even cooling, resulting in more efficient engine performance. In addition, the cylinder cooling system is easily removable to access the engine spark plugs and fuel injectors for inspection and routine maintenance while not requiring the spark plug wiring or fuel lines to be disassembled in any way.

A general purpose engine with a cleaning access window defined therein is in the form of an air cooled engine, having a cylinder unit made up of a cylinder and a cylinder head, and includes a housing for covering at least the cylinder unit and a cleaner covering removably fitted to the housing for covering the filter section of the air cleaner, the housing being formed with a blow window so as to confront gaps between a plurality of cooling fins provided in the cylinder unit, and the cleaner covering has a closing section defined therein for covering the blow window.

A hand-held work implement comprises a housing, at least one tool and a combustion engine for driving the tool. The combustion engine has a cylinder and has a piston which drives a crankshaft in rotation about an axis of rotation. The crankshaft drives a fan impeller. The work implement has a handle unit with a handle bar and has an engine unit, these being connected to one another via anti-vibration elements. The combustion engine has a transverse plane which encompasses the cylinder longitudinal axis and which runs parallel to the axis of rotation of the crankshaft. The transverse plane divides the work implement into a front region, in which a section of the tool that projects out of the housing is arranged, and a rear region. The fixing of the anti-vibration element to the cylinder is realized in the front region.