Pulsed-neutron experiments have been made on two organic-moderated and -reflected coupled cores of the ROSPO (a zero-power organic-moderated reactor) nuclear system in order to investigate their time response and to measure some kinetic parameters. At least for loose coupling, the fundamental mode has been observed to have two time-decay constants in any point of the system (except in the vertical symmetry plane), which are strongly interrelated. For two identical cores, these decay constants can give separate information on the intrinsic and coupling reactivity as well as on the reduced neutron lifetime of the system.