A drive transmission system for activating a cogged flexible transmission organ includes a support pulley borne idle on a drive shaft which contacts tops of the organ cogs at a calibrated circumference thereof which defines a predetermined winding radius of the flexible transmission organ. A cogged drawing pulley is mounted on the drive shaft and has cogs for enmeshing with recesses in the cogged flexible transmission organ for advancing the flexible transmission organ. The drawing pulley has cogs sized for enmeshing with the recesses of the cogged flexible transmission organ, such that tops of the drawing pulley cogs are displaced from bottoms of the drawing pulley recesses. The drawing pulley therefore cannot drag on the flexible transmission organ when the support pulley is not subject to drive torque.