MXA VIDEO: WE TEST A TWISTED BUILT YAMAHA YZ270F BIG-BORE
This isn’t our first rodeo building a big-bore YZ270F using the Cylinder Works full kit ($549.95), 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 were in the mood to R&D a totally new bike. So, we went with the next-best option—Jamie Ellis at Twisted Development. He is a master at finding the perfect power profile for his customers. So, we asked Jamie if he could make the tried-and-true Cylinder Works YZ270F top-end kit more powerful and broader at the same time. In essence, the engine of our YZ270F felt similar to a KTM 350SXF but with more excitement down low. Every MXA test rider loved this bike—after he put his earplugs in. We admit that it took a boatload of dough to complete this build, but we felt we had to. It was something that we yearned for. So, we had to build it at any cost.