  The Von K{\'a}rm{\'a}n Sodium experiment yields a variety of dynamo regimes,
when asymmetry is imparted to the flow by rotating impellers at different speed
F1 and F2. We show that as the intensity of forcing, measured as F1 + F2, is
increased, the transition to a self-sustained magnetic field is always observed
via a supercritical bifurcation to a stationary state. For some values of the
asymmetry parameter $\\theta$ = (F1--F2)/(F1+F2), time dependent dynamo regimes
develop. They are observed either when the forcing is increased for a given
value of asymmetry, or when the amount of asymmetry is varied at sufficiently
high forcing. Two qualitatively different transitions between oscillatory and
stationary regimes are reported, involving or not a strong divergence of the
period of oscillations. These transitions can be interpreted using a low
dimensional model based on the interactions of two dynamo modes.
