The dirt bike you ride now is the result of over 40 years of trial and error. When motocross started as a sport, bikes were really nothing special. Riders had to modify their regular street bikes to what they wanted. Like with most sports, as it develops, so does the technology. Motocross is no exception. Bikes became more lightweight, yet durable for extreme off-­road racing. Here are the bikes that we believe changed the world of motocross.   1. 1970 Husqvarna 400 Cross You may remember it from the 1971 classic “On Any Sunday” as the bike that Steve McQueen rode and made mainstream. Husqvarna was known only in racing circles in the 60s and 70s, and it wasn't until Edison Dye began importing the 250cc and 125cc bikes to the US that the brand really took off. In 1969, Husqvarna released the all powerful 395cc two­-stroke. The 400 Cross was more powerful, and Smith and Gunnar Nilsson rode the bike to victory in the 1971 Baja 1000. It is a timeless piece of motocross history and even sits in the Motorcycle Hall of Fame in Pickerington, Ohio.   2. 1973 Honda CR250 Elsinore Back in the 1970s, European bikes like Husqvarna and Maico dominated the scene. Honda was known for its scooters at the time, but when they released the Elsinore, it was light and fast and perfect for off-­road racing. It could reach speeds of up to 100 km/h (considered quite fast for its time) and didn't require any modifications to be race-­ready - a true motocrosser. It was Honda's first two-stroke and was named after the Elsinore Grand Prix. The Elsinore used all the latest technology, including better ergonomics and electronics. In 1973, the Elsinore cost $1145, but today they are valued between $10,000­$17,500 – if you can find one.   3. 1973 KTM GS 125 KTM started production in 1953 with only 20 employees producing three bikes a day. They won their first championship in 1954 and it was only uphill from there. The GS 125 marks an important turning point for the company as it was the first KTM to make it to the US and some say, transformed motocross in the country. The bikes were so popular that they started manufacturing them in the US in 1978. Interesting fact: KTM has always been known for innovation. These days, they are one of the few manufacturers still making and promoting two-strokes. But what's more is that they are trying to make them more environmentally friendly.   4. 1975 Yamaha YZ250 It wasn't long before the Japanese started to make more and more race-­ready dirt bikes. The first YZ250 was actually developed in the US by Don Jones for his son. The YZ250s introduced a lot of firsts to the world of motocross: reed valves, power valves, and mono-­shock suspension. The 1975 YZ250 was 8.5kg heavier than the 1974 to be able to support the carbon mono­-shock suspension. It could have been even heavier, were it not for the small holes that were drilled into the aluminium tank to help decrease weight without compromising its strength. But the improved dirt bikes came at a cost. In 1975, a YZ250 would set you back $1890.00, but you got the best bike money could buy.   5. 1982 Yamaha YZ250 Technology continued to improve, and the 1982 YZ250 was the bike that would shape motocross for the next twenty years. Why, you ask? While it was quite heavy and not as powerful, it introduced safety seats, the all-­new Yamaha Power Valve System and liquid cooling, as well as the modern two­-stroke engine we know today. Fun fact: liquid cooling was actually considered a waste on a 250. It was thought that the weight of the system outweighed the benefit. The Yamaha factory team switched back to air­-cooled systems for their race bikes.   6. 1988 Honda CR250R This was one of the most controversial dirt bikes ever made — and it was unlike anything that had ever been made before. It features the “low boy” bodywork, with lowered tanks. This low and narrow design offered the rider maximum control and movement. On top of all of that, it was one sexy bike. Unfortunately, most riders didn't actually like the bike. Its engine had slow power delivery and the new settings of the suspension were worse than the ‘87. Despite this, the bike showed a shift in manufacturing focus and Honda still sold thousands. It was a bike designed specifically for supercross.   7. 1998 Yamaha YZ400F The YZ400F was a true motocross bike. In the 90s, if you wanted a four­-stroke you either had to buy something European like the Husaberg or build your own from an enduro bike. The YZ400F changed all that. And what's even more interesting is that the prototype was engineered, designed, and built by a Yamaha engineer – Yoshiham Nakayama worked on the YZ400F in his spare time. The motor had a Genesis road race motor stuffed into a YZ chassis. The bike had a great motor, reaching up to 11,000 rpm, when 9,000 rpm was the limit at the time. The prototype was raced by Doug Henry and Andrea Bartolini, and then everyone just had to have one. And so, Yamaha released the bike in 1998. Despite the ultra powerful engine it was quite a heavy bike, but it paved the way for Yamaha's modern, lighter bikes. Some say this is the bike that changed motocross.   8. 2002 Honda CRF450R Lighter, smaller, and easier to handle, it wasn't until 2002 when Honda released the CRF450R that the brilliance of the YZ400F was finally surpassed. It fixed all the issues the YZ400F had - like braking, fueling hesitation, and starting. And riders used to a two-­stroke had a much easier time converting to the CRF450R than to the YZ400F.   As you can see, motocross has come a long way, and it's all thanks to the trial and error of those who raced before us. Did you ever own any of these bikes? What was the dirt bike that changed the sport for you? Tell us about your game-­changing dirt bikes in the comments.