I can remember this from my childhood. We didn't have one as it was a luxury feature on your typical suburban lawnmower. A neighbor had one however; and come to think of it, this was a technological marvel of the time.
The Briggs & Stratton wind-up starter, technically an impulse starter, was a mechanical alternative to the more common rope-pull recoil starters that persist to this day. (My cursed rototiller has a rope-pull). Anyway, in the 1960's this breakthrough allowed a user to start a lawn mower without yanking on a rope multiple times.
The technology relied-upon a spring that stored energy as it was wound with a crank. Flipping a release lever allowed the spring the snap back, spinning the crankshaft much faster than a yanking on a rope and starting the engine. The Briggs Easy Spin version incorporated a patented camshaft feature that kept the intake valve open slightly longer on the compression stroke thereby reducing the force needed to turn the engine over. Spiffy.
A victim of their own complexity and as electric starters became more affordable this technology fell out of favor. It persists - although you won't find it in your garage. In situations where there is no electricity (lifeboats, military applications, generators, disaster relief) impulse starters are used for diesel engines.
Speaking for myself, rope pull starters suck....










