Spark-ignited internal combustion engine operated with charge stratification

In a spark ignited internal combustion engine operated with charge stratification and including a cylinder head having a main combustion chamber, a cavity defined by surrounding walls of the cylinder head, and an auxiliary combustion chamber formed within a cup-shaped insert positioned in the cavity, the cup-shaped insert being thin-walled and having an opening providing a passage connecting the main combustion chamber and the auxiliary combustion chamber, an opening for receiving a fuel delivery device and an opening for receiving an ignition device;

• the improvement wherein:
• the cavity opens toward the main combustion chamber and the cup-shaped insert opens away from the main combustion chamber, the side wall of the cup-shaped insert having a plurality of regions spacedly arranged from one another and force-fittedly applied against the inner wall of the cavity to frictionally maintain the insert in the cavity.