In at least some implementations, a carburetor includes a body, a fuel pump diaphragm and a pressure pulse passage. The fuel pump diaphragm is carried by the body and defines in part a fuel chamber on one side of the fuel pump diaphragm and a pressure pulse chamber on the other side of the fuel pump diaphragm. The pressure pulse passage communicates the pressure pulse chamber with a pressure pulse source to provide pressure pulses in the pressure pulse chamber to actuate the fuel pump diaphragm. The pressure pulse passage includes an inlet communicating with a passage in which pressure pulses are present and the inlet is spaced from a surface defining the passage in which pressure pulses are present.

In at least some implementations, a carburetor includes a body, a fuel pump diaphragm and a pressure pulse passage. The fuel pump diaphragm is carried by the body and defines in part a fuel chamber on one side of the fuel pump diaphragm and a pressure pulse chamber on the other side of the fuel pump diaphragm. The pressure pulse passage communicates the pressure pulse chamber with a pressure pulse source to provide pressure pulses in the pressure pulse chamber to actuate the fuel pump diaphragm. The pressure pulse passage includes an inlet communicating with a passage in which pressure pulses are present and the inlet is spaced from a surface defining the passage in which pressure pulses are present.

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 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.

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.

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.

An apparatus for delivering a fuel-air mixture to an engine is provided. The apparatus includes: a carburetor having one or more passages and one or more chambers, wherein at least some of the passages and chambers are in communication with one another; and a fluid pump communicated with the carburetor and pumping fluid into or out of the carburetor to influence an fuel-to-air ratio of a fuel and air mixture delivered from the carburetor.

An apparatus for delivering a fuel-air mixture to an engine is provided. The apparatus includes: a carburetor having one or more passages and one or more chambers, wherein at least some of the passages and chambers are in communication with one another; and a fluid pump communicated with the carburetor and pumping fluid into or out of the carburetor to influence an fuel-to-air ratio of a fuel and air mixture delivered from the carburetor.