A piston assembly for a two-stroke internal combustion engine includes an upper part joined to a lower part by hybrid induction welding. The upper part includes an upper and lower walls radially spacing inner and outer walls to present an outer cooling gallery therebetween. The lower wall includes first portions extending radially inwardly from the outer wall to the inner wall above the skirt sections and second portions extending radially inwardly from the outer wall to the inner wall above the pin bosses. The first portions extend oblique to the center axis and undulate between the inner and outer walls to reduce the stiffness of the skirt sections. The second portions of the lower wall extend perpendicular to the center axis. Skirt sections of the piston include a lower portion with a greater radial thickness and containing ring grooves.

A throttle valve for an internal combustion engine provided with a valve body, a tubular feeding duct defined in the valve body, a throttle plate, and an actuating device which controls rotation of the throttle plate. The actuating device includes an electric motor and an actuating device conditioning circuit defined in the valve body. The conditioning circuit includes a tube made of a first material able to conduct heat, and the valve body is entirely made of a second metal material and is provided with a seat for housing the tube, in which is provided a layer of a structural and heat-conducting resin, interposed between the seat and the tube.

A cylinder head assembly includes a cylinder head having an igniter mount that forms a portion of a fireside surface of the cylinder head. The assembly further includes a sleeve abutting the igniter mount within an igniter bore in the cylinder head, such that the sleeve and the cylinder head together form an igniter cooling passage circumferential of the igniter mount, and extending axially between the sleeve and the cylinder head. The configuration of the igniter mount and sleeve improves heat dissipation and reduces likelihood of pre-ignition in an internal combustion engine.

The present invention suppresses leakage of combustion gas from a contact surface. A cylinder head (20) is attached to a cylinder block. The surface (26) of the side of the cylinder head (20) that is attached to the cylinder block includes a first region (AH1) and a second region (AH2) that has higher hardness than the first region (AH1).

A method for producing a piston of an internal combustion engine, with a cooling duct, may include producing a piston blank with a cooling duct, closing an inlet and an outlet of the cooling duct by at least one closure element, machine-finishing the piston blank, and removing the at least one closure element.

An object of the present invention is to, while forming a heat insulating layer on a squish area surface of a top surface of a piston main body, prevent generation of large cracks on the heat insulating layer and suppress damages and peeling of the heat insulating layer. To achieve this object, in the present invention, pressure is applied to a heat insulating layer provided on a top surface of a piston main body, that is, a pressing stress is applied to the heat insulating layer in advance.

An engine has a cylinder head defining an intake port with a roof defining first and second valve guide bores upstream of first and second siamesed intake valve seats for a cylinder. The head has first and second asymmetric fairings extending outwardly from the roof and positioned directly upstream of respective bores. Each fairing has an inner wall intersecting an outer wall along an upstream edge and an inclined planar roof wall extending between the inner and outer walls. A method of forming the cylinder head and engine is also provided by milling the fairings from a roof preform formed with the intake port of the head.

An internal combustion engine includes: a head cover covering a cylinder head; and a variable valve actuation mechanism. The variable valve actuation mechanism includes: a cam placed inside the head cover and rotating with a camshaft extending in a rotation axis direction; and an intermediate arm placed inside the head cover and sandwiched between the cam and a rocker arm. A pair of side through-holes, which are provided for a support rod supporting the intermediate arm to pass through, are formed in side portions of the head cover so as to face each other along the rotation axis direction.

A method of forming an engine is provided. A liner is cast with an outer surface with a first texture extending circumferentially from a first end to a second end of the liner. A circumferential section of the outer surface of the liner is coated with an insulative, thermoset material with a lower thermal conductivity than the texture. An engine and a cylinder liner for the engine are provided. The liner has first and second ends with an outer surface extending therebetween. An outer surface of the liner has axial sections defining a texture and an insulative thermoset coating to form material interfaces with the block with different thermal conductivities thereacross.

A piston for an internal combustion engine may include a shaft. A dual-layer coating with an inner layer and an outer layer may be applied to the shaft. The inner layer may include organic binders and solid lubricants. The inner layer may also include hard material particles of at least one of tungsten disulphide (WS.sub.2), tungsten carbide (WC), silicon carbide (SiC), and aluminum oxide (Al.sub.2O.sub.3). The outer layer may include inorganic binders, may be air-hardening, and may have a lower wear resistance than the inner layer.