In a combustion engine for motor vehicles a cylinder arrangement having a combustion chamber and a precombustion chamber in communication therewith and receiving the spark-plug with its electrodes, a first fuel supply or dosing arrangement opening into the combustion chamber and a second fuel supply or dosing arrangement opening into the precombustion chamber, an operating means associated with the first and second fuel dosing means and having a member following the different predetermined positions representative of the operating state of the first fuel supply or dosing arrangement, such member being constructed to define the operating state of the second fuel supply or dosing arrangement, wherein such member comprises a stem assuming different and predetermined axial positions and having a cross sectional profiling thereon, means coupled to the cross sectional profiling and defining the predetermined operating states of the second fuel dosing arrangement, and wherein further the cross sectional profiling is formed as a cam, an operating bar slidably mounted against the force of a spring transversely with respect to the stem, the camming being operatively coupled with such bar which in turn is operatively coupled with the second fuel supply or dosing arrangement.