For 25 years everyone knew a four-stroke was too heavy to win a motocross race. Then Yamaha built one — and handed it to a rider who'd just broken his back. How one bike ended the two-stroke era. . . . #OneLungRacing #2Stroke #yamaha #yz400f #doughenry #motocross #fourstroke #amamotocross #supercross #mxhistory #thumper #yz250 #dirtbike #motocrosshistory #vintagemx #yamahamotocross #comebackstory #motohistory #twowheels #racinghistory #wr400 #motocrosslife #bikelife #legendary