The YZ-Series Pedigree
Explore the YZ-Series model world
Murayama Yuki
YZ Chief Project Leader
Ogawa Takashi
YZ Product Planner
Foreword – A Constant Need for Upward Progress
A machine for motocross is designed for competition, and if you dig deeper than that, the ultimate goal of these models is to win races. The expectation to deliver results is the fate racebikes are born with, and just like how the racers who take these machines to the ragged edge are athletes giving their all toward claiming victory, the engineers at Yamaha also give their all to develop the best machine they can. At the same time, the word “victory” takes on a broader array of meanings for a production motocross bike.
Up until 2009, the YZ450F was still carbureted, but managed to win AMA Supercross and Motocross World Championship titles among a rapidly advancing field of fuel-injected 4-strokes in an impressive show of performance. However, these are the world’s premier series for dirt bike racing. A production machine available to general consumers needs to be capable of bringing victory to riders of wide skill levels—from casual riders to seasoned professionals—and thus needs to answer the needs of that same spread of riders. To raise the engine’s flexibility and truly pack the potential for victories, Yamaha decided to completely redesign the YZ450F with a new, fuel-injected engine.
However, discussions and debates arose among the developers, as they wondered if simply adding fuel injection to the engine and giving it more power would be enough. They saw a full ground-up redesign for the 2010 model year as a great chance to not only update the engine but also revamp the entire package with an eye on the future. From there, the team elected to do everything they could for this full model update, and following day after day of in-depth contemplation and deliberation, they settled on a new engine layout unlike any before it, using a forward-positioned intake and a rear-positioned exhaust port.
With this engine layout, the intake system is positioned in the upper-front area of the chassis and the exhaust system is located in the lower-rear. This creates a straighter line from the point of intake to the point of exhaust, which should lead to a boost in engine power, but having the intake at the front brought numerous difficulties with it, like making the chassis layout more complex, requiring other means to ensure sufficient air cleaner capacity, and somehow routing the exhaust system.
Furthermore, Yamaha’s core stance had been to discard the simpler option of just increasing engine power. Rather, the aim was to raise engine performance while simultaneously centralizing the bike’s mass to reduce the moment of inertia and yield higher agility and better handling behavior. To employ the forward-positioned intake/rear-positioned exhaust layout as well as achieve excellent mass centralization, a new bilateral beam frame was developed. Pairing this frame together with the new engine layout, the 2010 YZ450F successfully achieved a significant jump in performance, just as the engineers had intended.
However, this accomplishment was not the end goal, but rather the beginning of a long journey. While the 2010 machine greatly expanded the YZ450F’s possibilities as a competitive package, it also presented a new challenge: what is the right direction to go in if we are to further its development and progress? Fully exploring all its new possibilities and a long period of refinement was the only way forward in order to transform the YZ450F into a machine truly easy to go fast on by a variety of riders across a variety of racing scenes.
The Engine – Never-Ending Development Challenges
Once the 2010 model ushered in the forward-positioned intake/rear-positioned exhaust engine layout, subsequent YZ450F engines demonstrated its ample performance potential. Still, these sizeable 450cc engines can at times become a double-edged sword when riding off road. Simply packing gobs of power demands careful control of the throttle from the rider, and as this whittles away at their mental fortitude, it usually leads to fatigue. But at the same time, not having enough power means not enough speed on the straights, and that forces the rider to try to compensate for it in corners. On top of that, the bike is likely to lack good acceleration out of the corner.
From each year onward, development focused on making the abundant power provided by the forward-positioned intake/rear-positioned exhaust layout as manageable as possible. It started with revising the fuel injection settings for the 2012 model, and then came changes to the piston and intake/exhaust port shapes, bigger intake/exhaust valves, and a different exhaust pipe layout with the 2014 model. Then with the 2016 model, the cam lobe profiles and valve timing were changed, along with the adoption of a launch control system. The 2018 model gained a revised intake port and new piston design, together with a camshaft for higher valve lift. These and many other refinements were done over the years to provide an excellent balance of power and ease of use.
For 2020, the YZ450F became even more competitive through further power gains and lighter weight from an all-new engine, which featured a new piston, new cylinder head, and a more compact combustion chamber, which raised the compression ratio from 12.8:1 to 13:1. The head area was downsized to a millimeter scale for greater mass centralization, and more magnesium components used for the head cover to further reduce weight for the cylinder head assembly.
In the world of motorcycle racing, there is one thing that never comes—an end to progress. True to that, the 2023 model YZ450F came with more updates, including a new engine with further performance improvements, namely a whopping 5% more power and an additional 500 rpm to the redline. This extra pull at the top that the engine achieves becomes a serious weapon in the hands of the rider, as it gives them the option to keep the throttle open that little bit more instead of shifting gears. Depending on the situation, this not only reduces the total number of shifts needed but also gives riders more tools at their disposal, which means more chances to pass when locked in a battle with rivals. Also, thanks to a completely new crankcase and a thorough review to shave off weight throughout the entire machine, the latest YZ450F is a healthy 1.1 kg lighter than the outgoing model while being even more compact.
However, the engine alone is not the be-all and end-all. When creating a motorcycle, Yamaha does not treat the engine, chassis, electrics, exterior design, and other items as separate, individual elements. Although each engineer is a specialist in their respective field, they cast a wide gaze across the entire project while handling their own responsibilities in order to put together one cohesive machine.
If even a single thing sticks out, that cohesion is broken. All the engine advances and refinements mentioned so far were done in tandem with similar changes to the chassis, based on a strong awareness of the need to enhance the overall performance package.
With engines, “more power” is often treated as the golden rule for success. In reality, the rider’s feeling is the baseline for everything. Through repeated test runs and follow-up changes, developers do their utmost to bring the bike and its power delivery as close as possible to what “feels” right, something that cannot be boiled down to numbers. The road to making a powerful yet exploitable engine is by no means a smooth one. Similarly, the path traveled by the YZ450F’s powerplant has been a bumpy one, like blazing forward over a set of whoops. And with the 2023 model year, its development has reached yet another new high point.
The Aluminum Frame – Stalwart Stability
Since the 2006 model, the YZ450F has used an aluminum frame. The initial push to switch from steel to aluminum came from the desire to reduce weight as much as possible, as lighter weight brings significant as well as practical benefits with machines for competition, from better handling to reduced power loss. However, as the times change, so do the demands of these dirt bikes. In designing an aluminum frame for the YZ450F, Yamaha sought to retain the lightness aluminum frames are known for while tuning it for optimal rigidity, shifting the focus more toward greater controllability.
In 2010 when the engine received a major boost in performance, the primary goal for developing its aluminum frame was to enable the bike’s groundbreaking engine layout of a forward-positioned intake, rear-positioned exhaust, and rearward-inclined cylinder. With the engine layout being so drastically altered, this naturally meant the frame enclosing it would require its own significant changes. The bike’s bilateral beam frame had aluminum materials with different characteristics welded together to form a single unit, bringing a major change to it much like the engine’s. To further unlock its potential, it too has seen minor alterations and revisions year after year to tweak its balance and stiffness.
The YZ450F was fully redesigned for 2018 and featured an all-new aluminum frame that carried on the main concepts and features of the previous bilateral beam frame, such as excellent traction, shock-absorption, and a fine balance between agility and straight-line stability. Of those, improving shock-absorption was an area of particularly dedicated focus. Braking on a motocross bike loads the front end and it is easy for the bike to become unstable. However, this new frame was engineered to take on those loads and dampen the impact from bumps, allowing the bike to enter corners with the same degree of stability. To increase the load on the front, the engine’s rearward incline was also tilted upward, going from 8.2° to 6.2°.
To Yamaha, the ideal kind of handling is one that is completely rider-friendly. When the engineers set to creating a new frame, they aim for a design capable of dampening the effects of external forces. Motocross is an off-road sport with a wide variety of track surfaces, like dirt, mud, and sand, and courses are littered with whoops, ruts, and jumps of all sizes. Course conditions can also change drastically; dry surfaces can sometimes be nearly as hard as asphalt, while mud can get so thick that it’s a challenge just to get the bike moving.
If the bike is less susceptible to course conditions and has stable handling, it lowers the degree a rider needs to divert their attention and allows them to dedicate more mental focus to riding precisely for a longer time. If the machine always behaves in a way they can expect, that inspires greater confidence in the bike, making it easier for the rider to challenge themselves and push closer to their limits. Yamaha believes that this kind of character—a favorable mount that encourages the user—offers the best shortcut to winning races.
After the aluminum frame made another major step forward with the 2018 model, it received yet further refinements to its rigidity and balance for the 2020 version. As the latest 2023 model gained a new engine, the frame was modified accordingly, with the main spars lowered and other fine-tuning adjustments made to give the rider more freedom in their body positioning. Though each project team’s approach and methods may have changed over the years, the overall direction for frame development has never wavered: “Rider-friendly handling.” It may sound simple and straightforward, however, achieving it is anything but. The ideal frame is one usable by riders of any skill level—from beginners to seasoned professionals—and it allows them to ride exactly how they want, not only across many different off-road surfaces but also in ever-changing conditions. Striving to create such a frame is the goal chassis engineers for the YZ Series are constantly challenging themselves to achieve.
The Power Tuner – Simplifying Engine Adjustments
It goes without saying that a 4-stroke engine’s fundamental performance comes from the mechanical parts comprising it. Nowadays, however, computer-based tuning has such a heavy influence on engine character that it is no exaggeration to say that tuning itself decides much of that character. This being the case, it comes as no surprise that the demands made of engineers handling engine electronics—in both on- and off-road racing—have never been higher, and as the performance of computers has improved, so have their tuning capabilities. In step with that, the weight engine tuning has on race results has grown and so has the time and effort required to get it right. But, the ability to freely set up the engine’s characteristics to your preferences more than makes up for the hassle.
Besides its new fuel-injected engine, the 2010 YZ450F had another innovative feature: the Power Tuner. This dedicated handheld device eliminated the need to bring a laptop and cables to the dusty and dirty environment of a motocross track, and made adjusting a YZ’s engine mapping easy even for amateur racers. The Power Tuner enabled user customization of a YZ’s 3D fuel-injection and ignition timing maps, and with a wide range of adjustment points available, there was essentially an infinite number of possible combinations.
The 2018 YZ450F modernized the arrangement by wirelessly connecting the bike to a newly developed Power Tuner smartphone app. There was no longer any need for a dedicated device and cable to make map changes; customizing a YZ’s engine settings was now possible with just a smartphone. The app also raised the system’s level of functionality, offering more value ranges for even more detailed tuning possibilities. For example, with the 2010 model YZ450F, throttle opening and engine rpm were both uneditable, but these values were made changeable with the app. The goal in expanding the range of customization with the upgraded Power Tuner was to provide the tools for answering a rider’s most specific of demands.
Even back when the Power Tuner first appeared, it was immediately well received by the market; it essentially put the same level of tuning as a factory team into the hands of anybody who had it. Since it enabled the average user to customize their YZ’s engine settings however they saw fit, the Power Tuner was wildly successful in winning over hardcore dirt bike riders. Over a decade later when the development project for the 2023 YZ450F began, the development team decided to gather more customer feedback on the Power Tuner app and learned something unexpected. In reality, the feature used the most was the tracker for a bike’s running hours. It turned out that only a select type of customer regularly used the app’s engine tuning capabilities, which were arguably its standout feature.
Developing the Power Tuner app incurred its own share of costs as well, so during the planning stage, there naturally were discussions at Yamaha about whether it was worth it to put money into developing a feature that customers barely used. But neither Yamaha Motor USA, Yamaha Motor Europe, or any other subsidiary with YZs in their lineup voiced a desire to abandon the feature. Everybody involved—regardless of their role or rank—agreed that the Power Tuner was a valuable differentiator for Yamaha as an industry leader and had to be continued.
With that decided, the direction chosen was to update the Power Tuner app to be more user-friendly and to actively encourage customers to use it. From there, the team conducted further customer interviews, gathering input from not only motocross enthusiasts in and outside Japan but also from YZ riders within Yamaha itself to narrow down the best next step for the Power Tuner.
And so, the updated Power Tuner released for the 2023 YZ450F was the product of long hours and significant effort, gaining a simpler, easier-to-understand user interface while retaining the same advanced functionality as before. A quick setup feature for engine mapping was added, with a single slide bar for simpler, more intuitive tuning. The app also has a helpful set up feature where riders can select the issues they are facing and the app will offer solutions and adjustment advice for addressing them. As with the engine and chassis, even here, Yamaha’s development policy of offering excellent functionality with easier usability can be seen.
The Exterior Design – A Complementary Combination of Beauty and Functionality
To be extremely slim, extremely compact, and keep exterior parts to the absolute minimum is the mark of a motocross bike. You won’t find the margins or blank spaces typical for decorative appeal on this dirt bike, but the 2023 YZ450F still has Yamaha’s distinctive design language from every angle.
Surprisingly, the bike’s product plan did not list any design requirements whatsoever. Normally, the design process for a Yamaha sportbike often entails heated arguments between the engineers and designers, the two clashing for a rather simple reason: the engineers are unwilling to compromise on functionality while the designers are unwilling to compromise on the looks. However, this bashing of heads produces a beneficial synergy that, once applied to transforming a concept into a final product, often wins Yamaha bikes praise for their standout designs.
In other words, this cycle of “positive conflict” is how Yamaha’s engineers and designers come to understand one another. Armed with that mutual understanding, they move the project forward while endeavoring to satisfy each other’s vision for the final product.
As a dirt bike, the YZ450F does indeed already have little space available for design work, but even so, a product plan devoid of design goals or elements was still a very rare occurrence. But this was, in fact, the aim of its project planners. By purposefully not mentioning anything regarding its design, the planners had in effect communicated a different message: “Prioritize functionality above all else to craft features that constitute the true beauty of a YZ.”
The message reached the designers loud and clear, and they employed methods befitting a machine meant purely for competition. Functionality was the top priority in building the new 2023 YZ450F, and the resulting design truly reflects that approach. There were fewer clashes than usual between the engineers and designers—in a good way.
Still, the actual design work was quite challenging. Previous iterations of the YZ450F always tended to have a bulky look around the front end, something necessitated by the forward-positioned intake/rear-positioned exhaust engine layout. When riders sat on the bike, the bulk they saw in front of them would often give the impression that the bike was not actually nimble or agile.
Seeking to do something about this predicament, the front end was heavily revised. The width of the shroud was made 50 mm slimmer than the previous model, while its shape was redesigned to guide more air to the radiator. Furthermore, the height of the tank surface was lowered by 10 mm and the seat height made 5 mm higher. In addition to becoming flatter, a thorough review of the air intake design made the bulky-looking intake area in front of the fuel tank considerably more compact. The result of all these changes is a machine that not only looks lighter but also hints at how easy it is for the rider to move around.
In these ways, the YZ450F was given maximum attention to enhancing functionality while giving it uniquely Yamaha design appeal. Like threading a needle, the design work was an undertaking rooted in the little details across the entire chassis, and was only possible through the deep as well as mutual understanding the team arrived at from the numerous positive clashes between designer and engineer.
There was one occurrence during development that clearly captured this dynamic. First, the designers took the initiative and requested a structural analysis of a certain part. It was an attempt to work styling and design touches into a part after it had already been engineered for maximum lightness and just the right level of strength. In fact, the engineers had also made a similar proposal, stating that there was some room on that engine part to include some design touches, so once it had been confirmed that no weight would be added and no functionality lost, several parts were given decorative design additions to make them look more attractive.
It can certainly be said that the plethora of positive interactions such as these between the YZ450F’s engineers and designers are what imbue the bike as a whole with the visual marks of a Yamaha.
In Summary – Why We Seek Victory
For an off-road racing machine like the YZ450F, its reason for existing is clear: to take victory. But at the same time, it is a product available to the general consumer, and as such, not every owner will be able to win with it. Put simply, there is only one spot at the top of a race podium.
Yamaha wants to enrich the lives of avid motocrossers through our dirt bikes, and this is not a one-dimensional desire for riders to just be faster if they are on a YZ. Rather, through the incredible sport of motocross, we want enthusiasts to communicate more with friends and family, share moments of togetherness, and find personal growth by pushing their own limits—to enjoy life itself.
To rise to challenges and push forward with steadfast dedication—sometimes experiencing the bitter taste of failure along the way—before basking in the sense of achievement the sweet taste of victory brings atop the podium...
TEveryone involved in developing Yamaha motocross bikes wants the people who ride them to have these kinds of experiences, experiences that become treasured moments of their lives to be passed on to the next generation.
However, the only manufacturers allowed to say “winning isn’t everything” are the ones already winning. That is why the YZ450F, the flagship of Yamaha’s title-winning YZ Series of motocross bikes, will continue to evolve in its quest for victories, guided by the uniquely Yamaha compass of Jin-Ki Kanno.*
*The seductive exhilaration felt when one with the machine that is shared as a baseline when quantifying and integrating it into a Yamaha’s performance.
Products
- YZ450F
- YZ250F
- YZ250
- YZ125
