Question: When is an off-road bike not an off-road bike? Answer: When it’s a Yamaha YZ450FX. The FX, along with a whole class of “closed-course competition cross-country” products, might be what we dirt bike enthusiasts consider off-road, but Yamaha has to call it a race bike, according to the EPA. Closed-course bikes aren’t required to have noise and emission measures, while off-road, dual-sport and street motorcycles are. So, in the eyes of the people who regulate stuff, the YZ450FX is just like the YZ450F motocross bike. The WR450F, on the other hand, is a true-blue off-road bike tuned to be whisper quiet and smog-friendly. They are still very similar bikes, mechanically. What are the real differences, and which one is best for the trail? We got them together to find out.

Yamaha makes two off-road 450s that look almost the same but couldn’t be more different.

Motocross is the driving force behind almost all dirt bike advancement. That’s where the greatest demand for technology and innovation exists. Accordingly, the YZ450F motocross bike is the platform for both the YZ450FX and the WR450F. The FX is just much closer to the source. The power-producing parts of the FX and the motocross bike are identical. The head, the cams and the exhaust are all full strength. The mapping is different, although you can tweak the FX in any direction you like with the Yamaha Power Tuner smartphone app. A much more significant difference is the gearbox. The FX has a wide-ratio five-speed. First and second are much lower than those of the motocross bike, third and fourth are very close (although not exactly the same), and fifth is taller.

The Yamaha WR450F makes less noise than the average 110.

Yamaha uses the same KYB suspension components for both, but the FX gets softer spring and damping rates. The FX fuel tank is 0.6 gallons larger at 2.2 gallons, and then there are the usual accoutrements: a kickstand, an 18-inch rear wheel, a plastic skid plate and an O-ring chain. It doesn’t get a spark arrester, handguards, lights or any instrumentation. If you show up on the line of any motocross race, the FX won’t stand out. It looks just like any MX bike.

The Pro Circuit T-4 slip-on exhaust and GYTR Competition kit ECU boost the WR up to YZ-level power output.

Making the YZ450FX into an off-road bike isn’t just about making the EPA happy. It’s about making the bike more appropriate for real off-road riding, not just racing. Yes, the bike is quiet—extremely quiet. It also gets a very different power delivery. Yamaha did this without changing the piston, valve or cams. It’s all done with the pipe and electronically. Then Yamaha went a little further in consideration of what off-road guys might want to do. It has a radiator fan, a headlight, a taillight and an odometer. The suspension is another step softer, but the components are the same basic KYB units that come on the YZ450F motocross bike.

On tight trails, the WR is much easier to handle than the FX.

The required measurements for EPA approval are invisible—for the most part. The bike has no air pump, charcoal canister or O2 sensor, but it does still come with a throttle stop and an inner baffle. For years, Yamaha has had an internal policy of overshooting the regulatory mark. Without those items, the WR would still pass any sound regulations in the world. Yamaha still makes its customers remove the little pea shooter within the pipe and swap out the throttle stop in order to allow full throttle. It doesn’t make a lot of sense, but bureaucracy often has strange consequences.

Deep within the bike’s electronic brain there are more complex measures. Unlike the YZ450FX, the WR’s mapping is fixed. The fuel delivery and spark advance are locked in place, and there’s no compatibility with the Yamaha Power Tuner.

When you have these two bikes on the same ride, someone is going to feel left out. Despite being so similar, these bikes are completely different. The FX is essentially a motocross bike. Yes, the suspension is a little softer than that of the YZ450F, but not so much that you notice right away. Drop the FX into a motocross race and it’s right at home. You don’t notice the larger fuel tank (the 2.2-gallon capacity would actually be welcome to most MX riders). The gear ratios are apparent only if you drop into first gear by accident. On an MX track, first gear is like throwing out an anchor. It’s a granny gear.

Even hardcore motoheads will feel comfortable on the YZ450FX.

The FX’s moto heritage makes it a great bike for western trails. For fast trails, sandy two-trackers and steep hills, it’s perfect, and the suspension is ideal for tackling big whoops at high speed. The WR has a huge horsepower disadvantage in that setting. It can’t pull through sand as well, can’t climb hills as easily and can’t keep up in wide-open spaces. But, just as you might expect, the tables turn on slower, tighter trails. That’s the defining challenge in desert riding; it’s a land of extremes. Tight, rocky canyons make it clear that the FX’s horsepower isn’t always your friend. The transition between “off” and “on” isn’t especially smooth, and finding traction can be a challenge. On top of that, the FX heats up quickly, and the suspension doesn’t even try to pick up small rocks and stones.

That’s where the WR excels. You can gently roll the throttle open on a loose pile of rocks with a high expectation of forward motion. Where the FX will spin and dig, the WR will hook up and move ahead. Even though the two bikes have the same gear ratios, first gear is more useful and manageable on the WR because you don’t have to be so careful with the throttle. The WR’s suspension is also more effective at dealing with rocks and stones. The bike’s one real shortcoming in that environment is a lean stumble down low. It can occasionally cough and die. To be fair, the FX does the same thing, but you expect the WR to run better in that zone. The best way to summarize the strengths and weaknesses of each bike is to do it by speed. On any trail ride where the average speed is below 20 mph, the WR is going to be easier to ride and more fun. Above that, it’s all FX.

The Yamaha YZ450FX is a close relative of the YZ450F motocross bike but with more range, softer suspension, smoother power and a wide-ratio five-speed.

Off-road riders, in general, hate leaving anything alone. The knee-jerk tendency for most WR owners will be to look for more power. It ain’t easy. Yamaha has done a very good job of encrypting the ECU so that it can’t be reprogrammed, and any other modifications will be of limited productivity. Yamaha’s accessory division has a solution. The $150 GYTR Competition lit is a new ECU that isn’t locked and gives you the same mapping as the FX. We combined that with a Pro Circuit T-6 slip-on exhaust, which sells for $537, complete with spark arrester. Presto: the WR gains almost 20 horsepower. It runs even better than the FX, with a smoother transition off the bottom. It does lose something along the way, though. Horsepower is the enemy of handling; always has been, always will be. With the Competition kit and the slip-on, the WR is more difficult to manage in rocks and technical stuff. The softer suspension makes it easier to ride than a stock FX, but only by a slight margin.


If you want truly smooth, manageable power down low, you will have to dive into mapping. The Competition kit is programmable, but you still need one more piece of the puzzle. The GYTR communication unit sells for another $300. This is the device that allows the ECU to talk to any smartphone via a Wi-Fi signal. It comes stock on every YZ four-stroke but not on the WR. That opens up a whole world of opportunities. You can, for example, leave the stock quiet pipe in place and eliminate the low-end cough. You can also dial in the power for the Pro Circuit slip-on for a smoother low-end delivery.

So, back to the original question: WR or FX? The answer is in the mirror. If the guy staring back is a racer, the YZ450FX is a perfect match. It’s a great motocross bike, with the suspension and the fuel capacity to handle GPs and desert races. If that guy in the mirror is a trail rider, the stealthy nature and smooth power of the WR is what he needs. If he’s both, then he’s going to have to spend some money. You can start with the WR450F and have both bikes. The Competition kit, the Pro Circuit slip-on and the GYTR communication unit add around $800 to the price of the WR, which starts off at $9799 ($100 more than the FX). Yes, that’s a lot of money for a dirt bike. But, it’s cheap for two dirt bikes.

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