A lever for transmitting motion from an input wheel set pivoting about a first axis on a pivoting plate of the lever, to a receiver wheel set, the input wheel set permanently transmitting its motion to an output wheel set carried by the plate and pivoting under the action of the input wheel set about a second axis whose angular position is variable relative to the first axis, and the lever includes a first friction connection between a first friction surface of the input wheel set and a second friction surface of the plate, this first friction connection is weaker or stronger than a second friction connection between a third friction surface of the output wheel set and a fourth friction surface of the plate included in the lever.