Motocross had been exclusive territory to 2-stoke motorcycles much before the 1950s. In 1952, an individual European Championship that allowed the use of 500cc engine displacements was set up by the FIM and would, later on, be upgraded to World Championship status in 1957. However, in 1963, a significant moment in motocross history occurred that allowed 250cc 2-stroke moto-crossers to compete in the 500cc category fielded with 4-strokers.
Fast-forward to the early nineties in a competition of changing rules, the AMA, relaxed its rules that allowed 450cc 4-strokes to compete in the same class as the 250cc 2-strokes. Yamaha took advantage of the rule and developed the Yamaha YZ400F specifically for the category giving it a 5-valve head, liquid cooling, and a 12.5:1 compression ratio. In 1997, with the introduction of the YZ400M, Doug Henry rode it to victory at the Las Vegas Supercross, a first for a 4-stroker in an AMA event, and Yamaha has not looked back since then. With the introduction of the Yamaha YZ450F in 2003, and in its 13th generation, the Yamaha has clinched just about every major FIM Motocross and US Supercross title there is to win with 2-stroke and 4-stroke technology, ever since they won their first World Motocross Championship 50 years ago. Having put all their focus on the new 2023 Yamaha YZ450F, Yamaha has developed a motocross machine that is not only lighter, faster, and easier to ride but has been designed to live up to its heritage.
10 A New YZ450F Engine
Yamaha has redesigned the YZ450F’s engine which has remained unchanged since the introduction of the original reversed-head layout in 2010. With the usual head layout reversed instead of exhaust cams facing the engine forward, Yamaha’s tricks-in-the-bag has enabled them to keep the bulk of the YZS450F’s air-box, fuel tank, exhaust, and the slanting rear cylinder towards the bike’s center of mass. With a lighter and more durable engine designed to linearly deliver more output with better drivability, the Yamaha YZ450F is easy to ride throughout the rev range.
9 Redesigned Piston And Crankshaft
The YZ450F gets a newly designed piston and an optimized combustion chamber thanks to the reversed-head layout, as well as a lighter cylinder block that changes its power characteristics in the powerband to an extra 500 revs. The new engine is also equipped with a low-friction camshaft chain, re-designed crank and connecting rod assembly, lighter plain bearings, and a new balancer weight and hollow balancer shaft that negates out any engine vibrations
8 Improved Air-Intake And Routing With Vortex Airbox
For 2023, the YZ450F’s air intake ports have been redesigned and reshaped with a straighter passage to the cylinder head that increases air intake volume by 9% at maximum valve lift, thanks to a larger 39mm diameter intake valve. The exhaust port has also been reshaped to allow a better flow to the exhaust.
The YZ450F has a newly routed air-intake path between the fuel tank, frame, seat, and side panels that prevent the ingression of water, dust, and mud from entering the air-box. For 2023, YZ450F also gets a newly designed airbox that separates incoming dust centrifugally before reaching a new round three-dimensional air filter.
7 Newly Designed Transmission
With the YZ450F’s power up 5%, the transmission has had to be redesigned to compensate for this increase. The distance between the new transmission’s drive shafts has been widened, while each gear’s diameter has been increased to reduce weight and increase the overall strength of the 5-speed gear-box.
The clutch previously a two-piece steel aluminum component (coil spring) is now replaced with a light-weight one-piece steel clutch with disc springs. The 450F’s new clutch is 0.75 kg lighter, and slimmer providing a more direct feel and lighter pull at the clutch.
6 Redesigned Aluminum Frame
The 2023 Yamaha YZ450F’s aluminum beam frame has been improved to feel lighter while providing agility and stability at the same time. Yamaha’s engineers have relocated the joint between the tank rails and head pipe, which is now 15mm lower than its predecessor while the downtube, cross tube, and swingarm pivot area have been stiffened ensuring a high level of stability and precise cornering. The YZ450F’s chassis which originally had an 8mm aluminum front engine mount utilizing three through bolts, now gets a 4mm thick steel mount with one bolt.
5 Next Generation Bodywork
Every exterior panel of the Yamaha YZ450F has been redesigned to provide a slimmer body, making it more compact and sleek while allowing the rider to rapidly shift body weight. Because of the elimination of the front air-ducts, thanks to the newly routed air supply path, this has allowed more compact shrouds with a width reduction of 50mm to be fitted, as well as a narrower new fuel tank that makes the center section of the YZ450F slimmer. The YZ450F also gets a compact fender with a shorter rear fender to match, making the YZ’s overall length appear shorter.
4 Improved Ergonomics
The Yamaha YZ450F’s riding ergonomics, i.e., the connection between the seat, handlebars, and foot-rests has been revised to accommodate varying physiques. The seat height has been increased by 5mm while making the seat surface flatter and the rounded profiles of the left and right seat edges have been contoured better making lateral movement easier and more comfortable. The footrests are 5mm lower giving 10mm of more legroom (taking the seat changes into account) for taller riders while a 4-position adjustable rubber-mounted handlebar can be moved according to the size of the rider to provide a more neutral riding position.
3 Improved Suspension Valving
The Yamaha YZ450F’s KYB suspension valving has been upgraded to absorb high and low-speed bumps by simply hand-tweaking the adjustable compression damping adjuster which in turn has helped with the 450F’s cornering precision and straight-line stability. For more information on suspension setup, the rider can also access information and recommendations on suspension settings via the Power Tuner app on his or her smartphone.
2 An advanced Launch Control System
The YZ450F now has the ability to gain the holeshot at full throttle, thanks to a new Rev Limit feature in the Launch Control System that can set a maximum rpm between 6000 and 11,000 rpm in 500rpm increments. The Rev Limit feature automatically disengages once the LCS recognizes that the start has been completed and the bike has reached 3rd gear.
1 Power Tuner App
The Power Tuner app has been updated in an intuitive way that makes it easier to understand and use while selecting different levels of power, traction, and launch control just by scrolling a slider horizontally from Smooth through Aggressive – of course, this is only possible once the rider has downloaded the app and paired his phone to the YZ450F. Additional functions also include RPM, fuel consumption, a lap timer, speed, battery voltage, and a host of other data. An FAQ section also provides a guide on how to maximize the suspension setup. The Power Tuner app can be downloaded from Google Play or the Apple Store, depending on the rider’s smartphone’s operating system.