An apparatus and method for a differential stroke combustion engine. The combustion engine including one or more two-part pistons, each two-part piston having a first piston part and a second piston part. The apparatus comprising: piston-lever element mechanically coupled to the second piston part; a plurality of cam-followers assemblies selectively coupleable with the piston-lever element for controlling operation of the second piston part; and wherein selective engagement of one or more cam-followers assemblies defines an operational mode of the second piston part.