2021 Yamaha YZ450FX Review

Being that updates to Yamaha’s cross-country and enduro bikes fall one year behind those of the manufacturer’s four-stroke motocross models, the YZ450FX was due for a revamp in 2021. Sure enough, that’s exactly what the bLU cRU’s 450 off-road competition motorcycle was given. The YZ450FX was last updated in 2019, and it won Dirt Rider’s 450 Off-Road Shootout that same year, so the bike has proven its worth as a cross-country racebike model. How much better is the 2021 version? We were eager to find out for ourselves after dynoing, weighing, and measuring it, and quickly got to work testing it in the field.

If you follow the YZ450F’s progression, you’ve likely noticed the 2020 model received some major engine updates that improved Yamaha’s already strong 450cc powerplant. Those same changes were applied to the YZ450FX for 2021, including a more compact cylinder head that’s also lighter by more than half a pound, different camshafts, a new piston, and a longer connecting rod. On Dirt Rider’s in-house Dynojet 250i rear-wheel dynamometer, the 2021 YZ450FX produced 53.0 hp at 9,600 rpm and 32.9 pound-feet of torque at 7,100 rpm.

The ECU tuning is unique to the YZ450FX with off-road-specific mapping. The ability to make adjustments to the mapping via the Yamaha Power Tuner app is possible as the ECU is unlocked. The muffler, which has a baffle intended to reduce noise and smooth out the power delivery, is another YZ450FX-specific component. Being that this bike is an off-road competition model, the transmission is a wide-ratio five-speed with a low first gear and slightly lower second gear compared to the YZ450F. While the gaps between gears are slightly larger than in the motocross transmission, the engine’s strong torque completely blends them together. Naturally, the very low first is mainly a tractor gear for the tightest of sections. Second gear is good for starting and stopping, while third is mostly used for single-track riding. Its third and fourth gears are almost equal to those same gears in the motocrosser, while fifth is taller.

The changes Yamaha made to the engine are immediately noticeable. Right off the crack of the throttle, the power is very responsive and the seat-of-the-pants torque is amazing. It runs through the power at a reasonable rate unless you spin the rear tire, which can be easy to do. The power is strong enough that the bike can be a little hard to control in slippery conditions. The YZ450FX may not pull as long in the rpm range as a KTM 450 XC-F or Honda CRF450RX, but it will easily outdo all of its competition in terms of torque feel. Yamaha also improved on the YZ450FX’s starting capability; the engine fires to life quickly in neutral and even in gear.

The ECU mapping may be specific to the YZ450FX, but there’s still an abundance of power. At times, it was seriously more than I could hang onto. Adjusting the power is incredibly easy with the Power Tuner app. Unlike the YZ450F, the base ECU maps 1 and 2 are different: Map 1 is more aggressive for high traction conditions, while map 2 is designed more around extreme conditions when traction is limited and a smoother power delivery is warranted.

Selecting either map is easy and can be done on the fly. I tried both maps and made several adjustments, but I ultimately preferred map 1, with a few changes. My main goals were to achieve more controlled acceleration, better rear wheel traction, and less engine-braking. I would have liked to improve rear wheel traction a little more, because with the huge amount of power this engine is capable of delivering, you have to be careful not to give it too much throttle, especially if you are not going in a straight line.

Like the rest of Yamaha’s cross-country bike lineup, the YZ450FX is spec’d with a KYB Speed Sensitive System (SSS) 48mm coil-spring fork and KYB shock. Each has off-road-specific settings including different valving and spring rates from the motocross model of the same displacement. The YZ450FX uses 4.6 Nm fork springs (compared to the YZ450F’s 5.0 Nm) and a 56 Nm shock spring (where the YZ450F is spec’d with a 58 Nm).

The YZ450FX’s competition-bike nature is noticeable in the suspension, with settings that feel very close to motocross but with softer springs. While this sounds good, the YZ450FX is 8 pounds heavier than the motocrosser and therefore tends to ride a little low in the stroke. This can give the false impression that the suspension is stiff. If you’re a lighter rider, say less than 150 pounds, the stock spring rates might be OK for you; otherwise, stiffer fork and shock spring rates may be necessary.

RELATED: 2021 Yamaha YZ450FX Dyno Test

The suspension action is smooth and predictable throughout and offers good stability and control. Only on the biggest of impacts is there any concern of overloading it. We made some adjustments that yielded noticeable improvements in performance and comfort by stiffening the compression and opening the rebound front and rear. For the most part, we were trying to get the bike to ride higher in the suspension travel to provide a plusher, more comfortable ride.

Although we did not come up with a single best setting, as we had more than one test rider, we did get to a point where the bike was 90 percent where we wanted it. To find your own ideal setting, start adjusting in increments of two clicks on the compression and one or two clicks on the rebound, then go a few more until you feel comfortable.

The 2021 YZ450FX chassis may look the same as the 2019 and 2020 model, but several significant changes have been made; it now shares the same chassis as the YZ450F. The upper frame rail thickness is 0.5mm thinner; the tubing in the engine cradle area is 0.5mm thicker. The top triple clamp has a thinner shape to reduce rigidity, and the front axle features a 20 percent decrease in rigidity; both components are said to be lighter. The goal of these changes were mostly to improve comfort, as the chassis geometry has remained the same.

The front brake has a new larger-piston caliper (up from 22.7mm to 25.4mm pistons), 22.3 percent larger brake pads, and a new front rotor with 16 percent more pad contact area. The new 240mm rear brake rotor is 5mm smaller than the prior disc, while Yamaha claims the rear brake caliper and hanger assembly are lighter. The engine mounts are cross-country specific in an effort to improve stability and comfort over obstacles of all shapes and sizes.

The current-generation YZ450FX has a stable chassis with good cornering ability and a very distinct feel; you quickly realize it is still a full-on competition bike while riding off-road. The wheelbase feels somewhat shorter than a KTM 450 XC-F or Husqvarna FX 450, but not as short as a Honda CRF450RX or Kawasaki KX450X. Sitting on the bike certainly provides a sitting-in feel, which can easily be offset with a taller seat foam if so desired.

Although the YZ450FX’s fuel tank is 0.6 gallon larger than the YZ450F’s, the ergonomics are no different. Yamaha’s reverse engine design and their ability to extend the fuel tank lower instead of higher help keep it from protruding upward or outward at the front like the Honda CRF450RX’s. Overall, the YZ450FX is still a touch wider in the center portion of the bike between your knees when standing in comparison to the Austrian bikes.

A rider 5-foot-10 or shorter will fit well on the bike; however, a taller pilot may want to try a taller seat foam; Yamaha offers a fully assembled version of its own that is 0.75 inch taller than stock. The handlebar position is widely adjustable, as the triple clamps have two mounting positions and allow the mounts to rotate forward or backward. These four different positions let riders move the bar a total of 36.5mm fore and aft.

The YZ450F has been a top finisher in many previous Dirt Rider 450 Motocross Shootouts, but the YZ450FX has been a bit of a sleeper bike when it comes to off-road competition. It has a stable chassis, good cornering ability, and an absolute monster of an engine. Why wouldn’t you consider it? Strangely, it seems the YZ450FX is perceived as being big and lazy, which is certainly not the case. In fact, its design gives it a very planted feel while riding, helping it find traction in the slipperiest of conditions.

Overall, the 2021 Yamaha YZ450FX is undoubtedly an off-road racing weapon. Off the showroom floor, it’s doubtful you’ll need more power than the YZ450FX delivers, though you may want to consider changing the suspension spring rates to match your weight. But overall, this bike is super strong, stable, and planted. You can ride the YZ450FX a little harder with confidence, knowing that when you make a mistake, the bike is more recoverable and won’t penalize you the way a Honda might.

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