Um bei einem Membranvergaser, dessen membrangesteuerte Regelkammer (15) für Kraftstoff (K) über eine Anzahl von Kraftstoffkanälen (10,16,18,21) mit einem Ansaugkanal (1) für Luft (L) verbunden ist, bei gleichzeitig hohem Wirkungsgrad eine möglichst geringe Beschleunigungsverzögerung zu erreichen, sind erfindugsgemäß alle Kraftstoffkanäle (10,16,18,21) über deren gesamte Länge voneinander getrennt geführt. Dadurch werden sowohl ein Hauptkanal (10) als auch ein Leerlaufkanal (21) und jeder Teillastkanal (16,18) aus der Regelkammer (15) unabhängig voneinander mit Kraftstoff (K) gespeist. Da ein Eindringen von Luft (L) sowohl in den oder jeden Teillastkanal (16,18) als auch in den Leerlaufkanal (21) verhindert ist, bleibt jeder Kanal (16,18,21) während der gesamten Betriebsdauer vollständig mit Kraftstoff (K) gefüllt, so daß dieser bei plötzlichen Beschleunigungsvorgängen ohne Verzögerung in den Ansaugkanal (1) des Membranvergasers austreten kann.

Carburettor (1) for an endothermic engine (1a), having a float chamber (3) capable of receiving fuel (2) from an inlet (5) of the carburettor (1) and of feeding fuel (2) to an outlet (6) of the carburettor (1), the inlet (5) being engageable by a first pin (20) which is integral with a floating body (18) contained in the float chamber (3) and the outlet (6) being engageable by a second pin (24) which can be actuated by means of a first device (13) with a cam and rocker, a second device (14) with a cam and rocker being mobile in phase with said first device (13) with a cam and rocker to move a second body (45) inside the float chamber (3) to obtain determinate variations in the level of fuel (2) inside the float chamber (3).

A suction tube unit (16) connected between a cylinder block (12) and a carburetor (14) in a stratified scavenging engine (10) has a suction tube for mixture (30) made of an elastic material; and a suction tube for stratified scavenging air (32) made of an elastic material. The suction tube for mixture (30) and the suction tube for air (32) have, at respective inlet ends (30a, 32a) connected to the carburetor (14), respective wall portions (36, 38) which face each other and have complementary shapes. A clearance space (40) is provided between the wall portions (36, 38) of the suction tube for mixture (30) and the suction tube for air (32).

A two-stroke internal combustion engine having an air control arrangement which controls scavenging air flow during rapid engine acceleration to optimize the acceleration and maximum power output of the engine while maintaining low exhaust emissions from the engine. Desirably, the air control arrangement may comprise a valve that throttles the air passage to one half or less of its total flow area at a medium engine load or less and completely or fully opens at a medium engine load or more of the engine. Normally, the air control valve opens in unison with the throttle valve, but during rapid acceleration of the engine the air control valve opens later or more slowly than the throttle valve to control the supply of scavenging air to the combustion chamber of the engine thereby enhancing rapid acceleration of the engine.

A carburetor for an internal combustion engine with an accelerator fuel pump in the carburetor having a piston actuated by a cam on a throttle valve shaft and a ball between them. The axis of a pump chamber in which the piston is slidably received is offset from and eccentric to the axis of rotation of the throttle shaft so that little fuel is supplied to the operating engine by the accelerator pump as the shaft is rotated to move the throttle valve from its idle position to an intermediate position and most of the fuel supplied by the accelerator pump to the engine is delivered as the shaft is rotated to move the throttle valve from the intermediate position to its wide open throttle position. This provides a proper fuel mixture to the engine to accelerate it and avoids the problem of supplying an overly rich fuel mixture to the engine during acceleration and particularly if the operator moves the throttle valve several times back and forth between the idle and intermediate positions before moving the throttle valve to the wide open position to accelerate the engine.

A carburetor for an internal combustion engine with an accelerator fuel pump in the carburetor having a piston actuated by a cam on a throttle valve shaft and a ball between them. The axis of a pump chamber in which the piston is slidably received is offset from and eccentric to the axis of rotation of the throttle shaft so that little fuel is supplied to the operating engine by the accelerator pump as the shaft is rotated to move the throttle valve from its idle position to an intermediate position and most of the fuel supplied by the accelerator pump to the engine is delivered as the shaft is rotated to move the throttle valve from the intermediate position to its wide open throttle position. This provides a proper fuel mixture to the engine to accelerate it and avoids the problem of supplying an overly rich fuel mixture to the engine during acceleration and particularly if the operator moves the throttle valve several times back and forth between the idle and intermediate positions before moving the throttle valve to the wide open position to accelerate the engine.

Disclosed is an engine fuel supply apparatus which can be made smaller in size and in which the amount of fuel in an air-fuel mixture (13) can be increased with a fast response in correspondence with the operation of a throttle valve (23) when the engine (14) is accelerated rapidly. The fuel supply apparatus is provided with a fuel booster pump (16). A portion of an air-fuel mixture is introduced into a negative-pressure chamber (65) of the fuel booster pump via a negative-pressure chamber channel (38), and the fuel booster pump is actuated. The actuation forces air in a pump chamber (66) to flow into a pressure chamber (27), and fuel (12) in a fuel storage chamber (26) is temporarily supplied to a carburetor (11).

Especially applicable to motorcycle engines, it consists of establishing in the main conduct through which the air from the filter (FA) arrives, whose flow is controlled by a butterfly valve of gases or main valve (1), a secondary butterfly valve (2) that keeps each operation in functioning, be it in stationary or transitory regime, the opening being appropriate for producing the loss of load that, added to the Venturi effect generated in the conduct section downstream from the aforementioned secondary butterfly valve (2) and the loss the load of the air filter (FA), giving rise to the appropriate suction at the emulsioned fuel outlet (3), the fuel from a cell (4) of constant level being mixed with the air flow, joined to the atmosphere, such that the suction at the outlet (3) produces a flow through and controlled by the main distributor (5), which emulsioned with the air from the tube (9), equipped with transverse holes, discharges in the central conduct of the system (11) through the outlet (3).

A two-stroke internal combustion engine having an air control arrangement which controls scavenging air flow during rapid engine acceleration to optimize the acceleration and maximum power output of the engine while maintaining low exhaust emissions from the engine. Desirably, the air control arrangement may comprise a valve that throttles the air passage to one half or less of its total flow area at a medium engine load or less and completely or fully opens at a medium engine load or more of the engine. Normally, the air control valve opens in unison with the throttle valve, but during rapid acceleration of the engine the air control valve opens later or more slowly than the throttle valve to control the supply of scavenging air to the combustion chamber of the engine thereby enhancing rapid acceleration of the engine.

A stratified scavenging two-cycle engine, in which control of an air flow rate provides a favorable accelerating performance and can prevent deterioration of exhaust gas. The stratified scavenging two-cycle engine comprises a scavenging flow passage (3) for connection between a cylinder chamber (4a) and a crank chamber (1a), an air flow passage (2) connected to the scavenging flow passage (3), air flow rate control means (12) for controlling a flow rate of air fed to the scavenging flow passage (3) from the air flow passage (2), and mixture flow rate control means (11) for controlling a flow rate of mixture sucked into the crank chamber (1a) from a mixture flow passage (10). The air flow rate control means (12) throttles an air flow rate at the time of acceleration. Alternatively, the air flow rate control means (12) is opened later than the mixture flow rate control means (11) at the time of acceleration.