CARSON BROWN’S YZ300

Jamie Ellis and his crew at Twisted Development have their hands in just about every realm of two-wheeled racing when it comes to building high-performance machines that go fast. Test rider Carson Brown can ride just about anything on two wheels fast. You can probably see where we are going with this. We teamed up with Twisted Development to build Carson Brown a Yamaha to race the Wiseco Two-Stroke World Championship presented by Fasthouse at Glen Helen Raceway.

BIG BUILD

The Twisted Development crew can make anything go fast, and they have a track record to prove it. But, it takes more than a fast machine to win races—reliability, handling, dedication, a rider who wants to win and, of course, a little bit of luck never hurt. When building a bike to compete in any two-stroke Open class where there is no restriction on displacement size, finding the magic amount of “cubic capacity,” or “cc” as it is commonly referred to, is key.

Twisted Development’s solution to this mathematical equation was simple, or at least it sounded simple during our first conversation with Jamie that pretty much went like this: “No problem, guys, we got it all figured out. We will just build a YZ300 for Carson to race!”

Carrying out the actual solution was slightly more complicated than that. At the heart of this build is a mid-2000, aluminum-framed Yamaha YZ250 platform. And when it came to adding additional cc to the build, that was done with an Athena YZ300 big-bore kit. Athena offers a kit that includes a cylinder, head, top-end gasket kit, piston kit and power valves.

Most people would bolt on the Athena kit, throw some race gas at it and call it good, but not Twisted Development. That was just the starting point. Twisted has done a lot of research and development with this 300cc kit using top-level professional racers, along with average joes as well. The head is modified, and the cylinder is ported in-house using specifications they have developed with these modifications on the top end. The forged piston in the Athena kit is no longer used and is switched out for a cast piston that Twisted Development has produced using proprietary specifications. The Twisted Development piston will not work in the standard Athena 300cc kit.

The bottom end also received ample amounts of attention. The OEM Yamaha YZ250 rod is used, but the crank was balanced and gets a texture they refer to as “atomized.” This new texture aids in the atomization of the fuel, resulting in a more complete, cleaner burn. The entire transmission was polished, and a complete Hinson billet-proof clutch system from Hinson Racing was installed to transfer all the newly produced horsepower to the rear wheel.

A Moto Tassinari VForce intake system replaces the stock unit, and the stock carburetor jetting had to be modified to run on VP MXRO2 race gas and work with all the new engine modifications. The final step of power production was the addition of a special hand-built Pro Circuit works pipe and 304 factory sound silencer.

The chassis setup on Carson Brown’s race bike was pretty straight forward. Just like most pro-level riders, the wheels need to be beefed up, and this was done using a complete wheelset from Dubya USA that features Haan billet-aluminum hubs, oversized stainless steel spokes and Excel rims all blacked out. The wheels got wrapped with Dunlop MX33 tires.

Suspension needs were all handled by Enzo Racing. In the rear, a CNCmachined, billet-aluminum, performance shock linkage arm from Pro Circuit was used. The linkage is designed to stiffen up the initial part of the stroke and provide a more stable feel throughout. Carson Brown went for a drastically different look for the YZ300. An all-black Acerbis plastic kit was paired with a completely custom graphics kit from Fusion Graphix that featured some purple accents and embedded glitter flakes throughout. It was topped off with an allwhite Guts Racing gripper seat cover.

BIG RESULTS

The proof is in the results, and the results show Carson Brown as the 2023 Wiseco Two-Stroke world champion in the Open Pro class! As you can imagine, this machine is tailor-made for a professional-level rider specifically for this event, but Twisted Development says they have used this same performance engine platform for a variety of skilled riders, and they have all come away with smiles on their faces, just like Carson had on the podium. The engine performance is drastically different than the stock YZ250 in just about every aspect; it has more everywhere!

Right off the bottom, the Twisted Development engine makes usable power without the normal clutch influence needed when riding the stock YZ250, and the midrange of the powerband pulls as hard as any other two-stroke build we have tested in recent history. In certain maps of the Vortex ignition, the power might sign off slightly earlier on the top end than the stock YZ250, but you get there so much faster, so no one complained. Twisted Development does have maps that will let the bike over-rev longer if a rider wants that.

When it comes to producing power, Twisted Development delivered, and we were amazed during testing at just how knowledgeable the entire staff is about not only their engine packages, but general engine characteristics and how to achieve what we wanted.

It came as no surprise that the overall chassis and suspension setup of Brown’s race bike was on the stiff side for most of our test riders, but we were surprised that the harder and more aggressive the bike was ridden, the better it worked, and the more comfortable our test riders became. The Enzo-valved internals and Pro Circuit performance shock linkage made a good combination, and a little help with the race setup from Dave Dye went a long way in getting the bike dialed for Carson Brown as well.