The 7021RS walk-behind mower is powered by the innovative Briggs & Stratton 700 series DOV engine. Its ReadyStart automatic choke engineering means no priming or choking is necessary to start the engine. And a patented direct overhead valve system delivers greater torque with less vibration and noise than comparably-sized engines. AutoWalk self-propelled rear wheel drive system is activated by simply squeezing the trigger on the handlebar.