A simple engine, comprises (1) a cylinder, and a spark plug in the cylinder; (2) a carburetor, fluidly connected to the cylinder; (3) a primary air intake path, fluidly connecting atmosphere to the carburetor; (4) a carburetor bypass air intake path, fluidly connecting air to the cylinder without passing through the carburetor; and (5) a valve, along the carburetor bypass air intake path, for controlling the flow of air through the carburetor bypass air intake path.

A simple engine, comprises (1) a cylinder, and a spark plug in the cylinder; (2) a carburetor, fluidly connected to the cylinder; (3) a primary air intake path, fluidly connecting atmosphere to the carburetor; (4) a carburetor bypass air intake path, fluidly connecting air to the cylinder without passing through the carburetor; and (5) a valve, along the carburetor bypass air intake path, for controlling the flow of air through the carburetor bypass air intake path.

An air cleaner includes: a frame member equipped at an intake port of a carburetor and provided with an air inlet port; a filter held by a holding part included in the frame member; a lid member configured to cover a front face of the filter; and a screw with a knob, the screw being configured to connect the frame member and the lid member together. The frame member is provided with an insertion hole, where the screw with the knob is inserted, on the outer side of the holding part. The lid member includes a part to be connected, to which the screw with the knob is connected, the screw being inserted into the insertion hole from a side close to the carburetor . A knob part of the screw with the knob is disposed on the inner side of a circumscribed line between the lid member and the engine.

An air cleaner includes: a frame member equipped at an intake port of a carburetor and provided with an air inlet port; a filter held by a holding part included in the frame member; a lid member configured to cover a front face of the filter; and a screw with a knob, the screw being configured to connect the frame member and the lid member together. The frame member is provided with an insertion hole, where the screw with the knob is inserted, on the outer side of the holding part. The lid member includes a part to be connected, to which the screw with the knob is connected, the screw being inserted into the insertion hole from a side close to the carburetor . A knob part of the screw with the knob is disposed on the inner side of a circumscribed line between the lid member and the engine.

A choke valve structure includes an air cleaner body having a suction pipe portion provided on an end wall, a choke valve having a valve body allowed to adhere to a sealing surface formed around an opening, and a movement mechanism configured to move the choke valve along a direction parallel to the sealing surface such that the valve body moves in closing and opening directions. A blowing back prevention plate disposed on an axial line of the suction pipe portion to face the opening is provided integrally with the air cleaner body. A protrusion, allowed to come into contact with the blowing back prevention plate when the valve body moves in the closing direction, is provided on the valve body. The valve body is pressed against the sealing surface to adhere thereto when the protrusion conies into contact with the blowing back prevention plate.

A choke valve structure includes an air cleaner body having a suction pipe portion provided on an end wall, a choke valve having a valve body allowed to adhere to a sealing surface formed around an opening, and a movement mechanism configured to move the choke valve along a direction parallel to the sealing surface such that the valve body moves in closing and opening directions. A blowing back prevention plate disposed on an axial line of the suction pipe portion to face the opening is provided integrally with the air cleaner body. A protrusion, allowed to come into contact with the blowing back prevention plate when the valve body moves in the closing direction, is provided on the valve body. The valve body is pressed against the sealing surface to adhere thereto when the protrusion conies into contact with the blowing back prevention plate.

The intake structure for an internal combustion engine includes: a collision surface configured to face an inlet of a carburetor; a deflecting surface configured to deflect a blowback flow, which is to diffuse after colliding against the collision surface, in one direction along the collision surface; a receiving surface configured to receive the blowback flow deflected by the deflecting surface; and a fuel-accumulating surface formed below the collision surface. A first clearance between an air-guiding direction distal end of the deflecting surface and the receiving surface is brought into communication to a downstream side of a filter of an air cleaner in a fresh-air intake direction so as to act as a main intake passage for fresh air.

An air filter and carburetor arrangement includes a round filter and a round filter carrier having a filter plate. The round filter has a central filter axis, which lies at an angle to the filter plate. The carburetor has a carburetor body, in which an intake duct is configured with a duct longitudinal axis, and at one end of the intake duct on the carburetor body a filter connection side for the round filter carrier is configured, wherein the round filter carrier is fixed with at least one surface portion of the filter plate on the connection surface of the carburetor. The design is provided such that the duct longitudinal axis of the intake duct lies in the plane of the filter plate at a lateral distance (r) to the filter axis of the round filter fixed to the round filter carrier.

An air filter and carburetor arrangement includes a round filter and a round filter carrier having a filter plate. The round filter has a central filter axis, which lies at an angle to the filter plate. The carburetor has a carburetor body, in which an intake duct is configured with a duct longitudinal axis, and at one end of the intake duct on the carburetor body a filter connection side for the round filter carrier is configured, wherein the round filter carrier is fixed with at least one surface portion of the filter plate on the connection surface of the carburetor. The design is provided such that the duct longitudinal axis of the intake duct lies in the plane of the filter plate at a lateral distance (r) to the filter axis of the round filter fixed to the round filter carrier.

In at least some implementations, a carburetor has a metering system that controls fuel flow from a fuel source to an air-fuel passage. The metering system includes a metering diaphragm sealed to a body of the carburetor to at least partly define a metering chamber between the metering diaphragm and the body, and the metering diaphragm has a continuous layer and a discontinuous layer. The continuous layer is responsive to fluid pressure within the metering chamber and moves against the discontinuous layer to open a metering valve to allow fuel flow from the fuel source and into the metering chamber when said fluid pressure is below a reference pressure.