Two-stroke internal combustion engine

A method of starting an internal scavenging two-stroke combustion engine, the engine including a cylinder with a cylinder wall defining a combustion chamber, a crankcase, and a piston disposed in the cylinder, the method comprising:

• providing a fuel and air mixture inlet channel in fluid communication with the crankcase, the fuel and air mixture inlet channel being connected to a carburetor having a throttle valve;
• providing an airhead channel in fluid communication with an interior of the cylinder, the airhead channel comprising an air inlet valve, wherein the airhead channel is formed separately from the fuel and air mixture channel;
• and
• providing a crossover channel downstream of the throttle valve and the air inlet valve in a sidewall of the cylinder between the fuel and air mixture inlet channel and the airhead channel,
• wherein in response to the air inlet valve being in a closed position during startup of the engine, establishing fluid communication between the air and fuel mixture inlet channel and the combustion chamber via the crossover channel thereby leading a part of the fuel and air mixture into the combustion chamber.

A scavenging two-stroke internal combustion engine, comprising:

• a cylinder with a cylinder wall defining a combustion chamber;
• a piston reciprocally disposed within the cylinder;
• a crankcase including a crankshaft rotatably disposed therein, the piston being connected to the crankshaft by a connecting rod;
• at least one scavenger duct extending between the combustion chamber and the crankcase, the scavenger duct including a top port and a bottom port;
• a fuel and air mixture inlet channel in fluid communication with the crankcase by way of a fuel and air inlet port so that the fuel and air mixture inlet channel delivers a fuel and air mixture to the crankcase;
• and
• an airhead channel opening into the cylinder, the airhead channel comprises an air inlet valve, wherein the airhead channel and the fuel and air mixture inlet channel are formed separately one from another, wherein at least at startup of the engine, fluid communication is established between the fuel and air mixture inlet channel and the combustion chamber via a pair of recesses formed on an outer wall of the piston leading a part of the fuel and air mixture into the combustion chamber, the pair of recesses being separated from each other by a wall section of the piston.