Abstract: A four-stroke engine is provided and has a cylinder and a piston that delimits a combustion chamber and by means of a connecting rod drives a crankshaft disposed in a crankcase. To drive a fuel pump, the fluctuating inner pressure in the crankcase, in the valve housing or in a connecting passage that connects the two housings is utilized. For this purpose, a drive chamber of the fuel pump is connected via a pulse line with a crankcase, a valve housing or the connecting passage.

Abstract: An air filter housing is provided for an intake air filter for a carburetor of an engine. A clean air receiving chamber is formed in the filter housing and is delimited by a filter element. Opening into the clean air receiving chamber is an intake opening that connects the air filter to the intake channel of the carburetor. A hood-like deflection bowl covers the intake opening in the clean air receiving chamber. The peripheral wall of the deflection bowl has a communicating window disposed transverse to the intake channel and serving for flow connection to the clean air receiving chamber. The communicating window opens into a compensation chamber that is separated from the clean air receiving chamber and communicates therewith via a channel.

Abstract: The invention is directed to a reciprocating internal combustion engine including a four-stroke engine. A longitudinally movable piston drives a crankshaft via a crank drive and a connecting rod. The crankshaft is journalled in a crankcase containing a lubricating oil for the crank drive. The chamber containing the lubricating oil is formed adjacent the cylinder by barrier walls within the crankcase as an oil receptacle to hold the lubricating oil in the overhead position of the cylinder. The crankcase is configured to have a trough-like shape and holds the lubricating oil and the cylinder projects axially into the crankcase and defines the barrier wall of the oil receptacle with its cylinder jacket. In this way, adequate lubrication is guaranteed in every operating position of the engine.

Abstract: The invention is directed to a mixture lubricated four-stroke engine having a cylinder and a piston which delimits a combustion chamber in the cylinder. The piston drives a crankshaft via a connecting rod with the crankshaft being journalled in a crankcase. An inlet valve and an outlet valve are provided for the combustion chamber and have respective valve members which are actuated via a valve drive assembly driven by the crankshaft. The inlet valve is connected via an intake channel to a mixture-preparation device. The valve housing is, on the one hand, connected to the crankcase and, on the other hand, is flow connected via a connecting channel to the intake channel. The crankcase is connected to the mixture-preparation device exclusively via the valve housing, the connecting channel and the intake channel. In this way, an adequate lubrication and excellent acceleration performance is ensured with a constructively simple configuration and excellent exhaust-gas quality.