Prior to 1997, 4-stroke dirt bikes were for recreational woods and trail riding with your friends. They might go years before needing any major engine work. If you wanted to race motocross, you rode a 2-stroke.
That was the case until April of 1997 when Yamaha factory rider Doug Henry showed up at the Las Vegas Supercross event with Yamaha’s prototype 400cc 4-stroke single cylinder motocross bike. People shook their heads, laughed and asked him if he even thought he would qualify with “that thing”. Doug let the bike do the talking – he got the holeshot which immediately opened up to a two second gap, won the race and the motorcycle industry never looked back. Within a few years every major dirt bike manufacturer had 250cc and 450cc 4-stroke dirt bikes. Honda went so far as to completely cease production of all 2-strokes.
Today, 4-stroke dirt bikes are ridden in just about every country on the planet. These small, high speed, single-cylinder engines are also used in ATVs. Multi-cylinder versions are used in 2, 3, and 4-cylinder side by sides, street bikes, watercraft, snowmobile, mini sprints, micro sprints, legends cars, karts and open wheel road race cars. Some of the side-by-sides and watercraft applications even come equipped with turbo or supercharged packages.