The first demonstration of a 40 μm core homogeneously ytterbium-doped fully-aperiodic large-pitch-fiber (FALPF) laser is reported on here. In this concept, the amplification of unwanted high-order modes is prevented by means of an aperiodic inner cladding structure, while the core and inner cladding material has a higher refractive index than pure silica. In a laser configuration, up to 252 W of extracted power, together with an optical-to-optical efficiency of 63 % with respect to the incident pump power, have been achieved. While an average M² of 1.4 was measured, the emitted power becomes temporally unstable when exceeding 95 W, owing to the occurrence of modal instabilities.