Schelkunoff's method, also commonly refered to as Coupled Mode Method (CMM), is a numerical method which gives the propagation constants and the electromagnetic field in a general homogeneous medium bounded by perfect electric walls. In this paper, we test Schelkunoff's method for a waveguide filled with an isotropic chiral material (chirowaveguide) where the dimensions of the walls are electrically large compared with the wavelength. It is reasonable to foresee that, in this case, the results given by Schelkunoff's method must approach to the corresponding ones for the chiral unbounded medium. Effectively, we obtain the solutions for both circular polarized waves (right-handed and left-handed) in free propagation in a single calculation. These results are in opposition with those of other authors analyzing analogous cases.