A speed control mechanism for controlling selective engagement of the self-propelledtransmission assembly for a walk-behind lawn mower is provided. The speedcontrolmechanism is also configured to control the relative output speed of thetransmissionassembly. The speed control mechanism includes a speed engagement assembly(33) anda speed adjustment assembly (32), wherein the speed engagement assembly (33)includesa pair of rotatable levers (34, 36) for causing the transmission assembly toactuatebetween a disengaged position and an engaged position and the speed adjustmentassembly (32) includes a rotatable knob (42) for causing the relative outputspeed of thetransmission assembly to the wheels of the lawn mower to increase or decrease.
