The Yamaha YZ250F is the most popular bike in the 250 class. It won our 2021 MX shootout and it’s one of the most successful bikes in Pro motocross. But all is not perfect in YZ land. The Yamaha has less top-end power than the KTM, Husqvarna, Kawasaki and Honda. What’s it take to bring the YZ to the next level? We go to the engine builders at Race Tech to find out.