An internal combustion engine (10), including a cylinder (15) with a cylinder wall (12) defining a combustion chamber (32), a piston (13) reciprocally disposed within the combustion chamber (32) a crankcase (16) including a crankshaft (11) rotatably disposed therein, the piston (13) being connected to the crankshaft (11) by a connecting rod (17), a first scavenger duct (3) extending between the combustion chamber (32) and the crankcase (16), the first scavenger duct (3) including a top port (31a) and a bottom port (31b), a fuel and air inlet channel (22) in fluid communication with the crankcase (16) by way of a piston ported fuel and air inlet port (23) so that the fuel and air inlet channel (22) delivers a fuel and air mixture to the crankcase (16), and an airhead channel (6) in fluid communication with the first scavenger duct (3) by way of a first piston ported air inlet port (7), characterized in that the fuel and air inlet channel (22) is in fluid communication with the airhead channel (6) so that the fuel and air mixture is combinable with the air flow from the airhead channel (6).

A carburetor for the combustion engine in a handheld work apparatus has a carburetor housing in which a carburetor drum is mounted rotatably about a pivot axis. The carburetor drum has a drum body which has at least one channel which runs transversely with respect to the pivot axis and forms an intake channel portion. A sensing unit for sensing at least one rotational position of the carburetor drum is provided. The sensing unit includes a control contour and a sensing device interacting with the control contour. The control contour is formed on the carburetor drum. A method for operating a combustion engine makes provision for the control device to control the supplied quantity of fuel depending on the rotational position, sensed by the sensing unit, of the carburetor drum.

An apparatus and methods are provided for an air cleaner to be mounted onto an air inlet of an internal combustion engine. The air cleaner comprises an air filter that includes a filter medium disposed between a curved base and a cover. The curved base provides an interface between the air filter and the air inlet, and comprises a shape that provides clearance between the curved base and an electric choke installed onto a carburetor comprising the air inlet. The cover secures the air filter and the curved base to the air inlet such that an airstream is drawn through the filter medium and is conducted into the air inlet. A raised portion of the cover is configured to cooperate with the curved base to ensure a desired volume of the airstream is available to the air inlet at substantially all engine speeds.

A suction tube of a stratified scavenging engine that can improve the flexibility in designing the shapes and layouts of an air-fuel mixture passage and an air passage; allow for continuous and smooth changes in the shapes of the cross sections of the air-fuel mixture passage and the air passage from the inlet side toward the outlet side; reduce the number of components; and facilitate attachment and assembly; and that is also advantageous in terms of cost is provided. The suction tube includes an air-fuel mixture passage and an air passage, inlet and outlet sides of the passages being connected to a carburetor and a cylinder, respectively; a cylindrical exterior member that mainly forms an outer perimeter portion of each of the air-fuel mixture passage and the air passage; and an interior member for dividing the inside of the cylindrical exterior member into the air-fuel mixture passage and the air passage. With the use of elastic deformation of the interior member or the cylindrical exterior member, the interior member is attached to and integrally formed with the inside of the cylindrical exterior member.

To improve the effect of preventing contamination of an element in an air cleaner. An air cleaner includes a first inlet (60) through which air is fed to an intake system air passage and a second inlet (62) through which air is fed to an intake system air-fuel mixture passage. An extended passage (72) leads to the second inlet (62), for example. A passage forming member (70, 204) forming the extended passage (72) is shaped to surround a periphery of the first inlet (60). The passage forming member (70, 204) forms a blown-back fuel diffusion preventing region (74) leading to the first inlet (60).

A backpack type blowing apparatus includes an intake pipe that connects an air cleaner fixed to a fan case of an air blower to a carburetor that supplies an evaporated fuel to an engine body, and a top cover fixed to the fan case to cover at least the intake pipe by interposing the intake pipe between the top cover and the fan case. The top cover has a plurality of cover fixing portions fixed to the fan case. An outer circumferential-side fixed portion positioned on an outer circumferential side of the intake pipe in the fan case is included in the plurality of cover fixing portions.

A carburetor achieves better emission characteristics while improving a combustion state by increasing a delivery ratio of a stratified scavenging engine and reducing intake resistance. No dividing wall is provided between a throttle valve 204 and a choke valve 242, and a gap 244 between the valves 204 and 242 is opened. Intake air in both of an upper region and a lower region of the choke valve 242 flows into an air-fuel mixture passage 246 in a lower region of the fully-open throttle valve 204. A main nozzle 202 is arranged so as to be inclined toward the throttle valve 204.

To allow an intake negative pressure to directly act on a fuel outlet formed on a nozzle tube, and to guide a fuel discharged from the fuel outlet in the nozzle tube to the fuel-air mixture passage. A rotary carburetor (200) has a guide plate member (42) downstream of a fuel outlet (30) located in a through-hole (14). The guide plate member (42) has both side edges (42b) away from an inner wall surface (14a) of the through-hole (14). The through-hole (14) is divided by the guide plate member (42) into a first passage portion (44) and a second passage portion (46). The first passage portion (44) communicates through a piston groove with a scavenging passage of a cylinder. The fuel discharged from the fuel outlet (30) is guided by the guide plate member (42) to the second passage portion (46) and is supplied through the second passage portion (46) to a fuel-air mixture passage (24) of an engine intake system.

A suction tube unit connected between a cylinder block and a carburetor in a stratified scavenging engine has a suction tube for mixture made of an elastic material; and a suction tube for stratified scavenging air made of an elastic material. The suction tube for mixture and the suction tube for air have, at respective inlet ends connected to the carburetor, respective wall portions which face each other and have complementary shapes. A clearance space is provided between the wall portions of the suction tube for mixture and the suction tube for air.

An internal combustion engine (10), including a cylinder (15) with a cylinder wall (12) defining a combustion chamber (32), a piston (13) reciprocally disposed within the combustion chamber (32) a crankcase (16) including a crankshaft (11) rotatably disposed therein, the piston (13) being connected to the crankshaft (11) by a connecting rod (17), a first scavenger duct (3) extending between the combustion chamber (32) and the crankcase (16), the first scavenger duct (3) including a top port (31a) and a bottom port (31b), a fuel and air inlet channel (22) in fluid communication with the crankcase (16) by way of a piston ported fuel and air inlet port (23) so that the fuel and air inlet channel (22) delivers a fuel and air mixture to the crankcase (16), and an airhead channel (6) in fluid communication with the first scavenger duct (3) by way of a first piston ported air inlet port (7), characterized in that the fuel and air inlet channel (22) is in fluid communication with the airhead channel (6) so that the fuel and air mixture is combinable with the air flow from the airhead channel (6).