In the mid-1990s, two-stroke motorcycles ruled motocross and Supercross because of their light weight and explosive power.
There were four-stroke motorcycles around at the time but they were trail bike and dual-sport machines.
Photo courtesy Yamaha
Then, in 1997, Yamaha unleashed the one-off YZM400F. Here are some things that made that bike so special.
1. This was the first Yamaha factory MXer with a four-stroke engine.
2. Racers Andrea Bartolini and Peter Johansson won four and two motos respectively in the 500cc Motocross World Championship before the bike was handed over to future AMA Motorcycle Hall of Famer Doug Henry.
3. To encourage development of new race-proven technology, in 1997 the AMA started offering manufacturers a one-year exemption to a long-time rule that required teams to start with production motorcycles when building their race bikes. Yamaha was the first company to take advantage of that rule and rolled out this exotic machine for the 1997 AMA Motocross Championships.
4. The YZM400F featured a hand-built main frame; a carbon-fiber subframe, airbox and engine mounts; magnesium clutch and flywheel housings; a hand-built aluminum gas tank; a titanium and carbon-fiber exhaust system and a four-speed transmission.
5. The bike debuted at the Gatorback Cycle Park outside Gainesville, Fla., where Henry rode it to eighth-place overall. He followed that up with a fourth overall in Sacramento, Calif. and then a sixth overall in San Bernardino, Calif.
6. But the YZM400F’s biggest race was the next weekend when the AMA pros headed to Las Vegas to put the wraps on the 1997 AMA Supercross Championship. Henry won on this machine, giving Yamaha a huge victory and showing the world that a four-stroke could beat two-strokes on their own turf.
7. Within a few years, four-strokes, not two, dominated professional motocross and Supercross competition, and it all started with Henry and the YZM.