Priority #1 for Yamaha’s YZ250F motocross bike in 2017 was to extract even more juice from the YZ-F’s 250 cubic centimeters. To do that Yamaha made a few big changes, like a revised cylinder head with new cams, valve angles, reshaped ports, and a shorter intake. The cases are said to be stronger, too, and the material and shape of the connecting rod has been upgraded. In order to extract the most from the mechanical changes, the ECU has been remapped, and the transmission has been made burlier. The result, says Yamaha, is more power between 7,000 and 14,000 rpm.