Twisted Yamaha YZ270F Project Build - Motocross Action Magazine

#motocross #dirtbike #racing #motorcycle This isn’t our first rodeo building a big-bore YZ270F using the Cylinder Works full kit ($), which is why we wanted to do it differently this time around. The YZ250F is known for its robust low-to-mid power. When you add in a bigger piston and equally big cylinder, the already-short and focused powerband can shrink into a narrower window. Yes, the YZ270F is even more explosive out of the hole, but it chunks up the already-short power curve. The bigger piston has to push more air per stroke, which makes it struggle to carry speed at high rpm. The lack of over-rev means that the rider has to shift on the bubble. This style of power can boss a rider around if he doesn’t bow down to its imperfections. We wanted the best of both worlds—in short, a YZ250F big-bore with a powerband that was linear and revved to the moon. Was it possible? We knew building a big-bore engine from the ground up was the way to go; however, we didn’t think Yamaha’s pencil-pushers wer