Honda, Suzuki and Yamaha all offer legitimate off-road 450s that occupy the ill-defined territory between closed-course competition bikes and dual-sport bikes. The Honda CRF450X is the descendant of the original Honda 450, unchanged for years, carburetor and all. It’s the current king of Baja and has become iconic in the off-road world. The Suzuki RMX450Z is making its second appearance in the U.S. after getting caught in bureaucratic limbo back in 2010. Yamaha has offered the WR450F continuously for years, but the current model has new technology and is a legitimate trail bike. Interestingly enough, all three are based on non-current MX designs but have been completely and thoroughly transformed for their new purpose.

For just a moment let’s return to the real world where politics, bureaucracy and regulation matter. In order to sell a motorcycle in the U.S., a manufacturer must declare the bike’s intended purpose. There are three categories— street-legal, off-road and closed-course. The regulations for street-legal and off-road bikes are converging, whereas the closed-course designation is still pretty much the Wild West. KTM and Husqvarna decided not to play the game anymore. They only offer street-legal bikes and closed-course bikes—and yes, all two-strokes fall into the latter category, even the EFI ones.
What that means to us, the riders, is still vague. California is the only state with any kind of enforcement mechanism. Other states have talked about it, but there are no practical consequences to riding an MX bike on public land. Well, actually, that’s not true. There is one very real consequence—MX bikes make crummy trail bikes. Even the ones that are supposed to be repurposed for off-road mostly have MX gearboxes, MX mufflers, MX fuel tanks and MX suspension. So, that’s why the regulations are only a side issue here. These three off-road motorcycles are here because they’re needed.

Back in 2005 when Honda released the first CRF450X, it was a very big deal. It was an electric-start off-road bike that offered so much more than the XR400R it replaced. Within two years it would also serve as the default replacement for the XR650R. Consequently, Honda’s in-house Baja team would start riding a 450, a concept that changed the way riders thought about racing in Mexico. The bike was heavily re-engineered in 2008, but it didn’t look all that different. It was brought up to the off-road emissions standards of the day, and the California model and 49-state model became one and the same. Regardless of where the bike is sold, it has a pump that feeds air into the exhaust, theoretically making for a more complete burn after combustion.

Honda CRF450X—weight without fuel: 259 pounds; MSRP: $8699.
Honda CRF450X—weight without fuel: 259 pounds; MSRP: $8699.

The rules are hard to understand, but, apparently, one reason the bike hasn’t changed since 2008 is because it’s grandfathered in under 10-year-old emission requirements. That’s why it doesn’t need fuel injection or a throttle limiter. The single-overhead-cam motor is fed by a Keihin FCR carburetor. It has a fixed needle and fuel screw. The exhaust has a baffle that’s connected to the spark arrester and most of the muffler internals. It can be removed, but there’s no point. The bike doesn’t run well that way. Contrary to what you might think, the EPA is also concerned with noise, and the Honda meets those standards legitimately without any fake measures that the owner has to defeat. In fact, the Honda is the only bike in this test that runs absolutely fine as it’s sold, and it’s whisper quiet. The low-end power, in particular, is excellent. The bike pulls well off the bottom without any glitches or hesitations. When we lament the passing of legitimate off-road 450 four-strokes, this is what we miss. The Honda 450X is much, much easier to ride at low speed than any of the current 450 motocross bikes. The power delivery is smooth, and it doesn’t hiccup or backfire despite being emissions compliant. First gear is much lower than that of a motocross bike too. The Honda’s five-speed gearbox is well thought out with fairly even spacing. Unfortunately, the motor goes flat as the revs climb. That’s where you pay the price for the restrictions. The power that seems so promising when you first open the throttle simply doesn’t build and acceleration suffers. The bike will only pull top gear on a hard, level surface.

The Honda CRF450X is one of the last carbureted off-road bikes.

Overall handling has always been this bike’s strong point. The frame is very similar to that of the 2008 CRF450R, a bike many people still consider to be one of the best motocrossers ever made. It’s stable and reasonably agile. In the case of the X, its weight is its biggest enemy. It weighs 259 pounds without fuel. By the standards of 2005, this was great for a four-stroke. Today, we know better. If you wanted to shave off a few pounds, you might remove the kickstarter or, conversely, you could disable the electric starter and remove the battery and starter motor. Either move offers very limited gains.
It’s interesting that the weight probably helps the Honda’s suspension. The bike is the very definition of plush. Both ends have Showa components with legitimate off-road settings. That means the bike is soft, but not so soft that it wallows. It soaks up rocks and little impacts extremely well and is well balanced. The bike is also good in big whoops. What it doesn’t like is any big jump landing or hard braking bumps. If you’re doing that kind of stuff, you’re getting out of the X’s territory and maybe you need more of a race bike.

Suzuki reintroduced the RMX450Z after a seven-year break in production. Gary Sutherlin will be defending his WORCS and National Hare & Hound championships on one.
Suzuki reintroduced the RMX450Z after a seven-year break in production. Gary Sutherlin will be defending his WORCS and National Hare & Hound championships on one.

If there were ever a bike to bring home the fact that times have changed, it was the 2010 Suzuki RMX450Z. It was Suzuki’s replacement for the DRZ400 of 10 years earlier, but the rules had changed dramatically since then. The RMX was an electric-start, fuel-injected 450 that met all the new noise and emission standards. It had a frame based on the 2009 RMZ450 MX bike with off-road-appropriate Showa suspension. The problem was that the people at Suzuki wanted to make it easy to upgrade the bike’s performance. As delivered, it had a throttle limiter, an inner exhaust baffle, a restrictive airbox lid and a very lean fuel map in the bike’s central processor. Suzuki was up front in telling customers how to change these things. What got them in trouble was that they preprogrammed a richer fuel map into the processor. In order to access it, you installed an inexpensive Yoshimura product called the “Cherry Bomb.” The fact that the richer map was pre-installed was against the rules, even if that map was never accessed. That triggered a recall that led to the bike’s ultimate disappearance from American dealerships.

Suzuki RMX450Z—weight without fuel: 263 pounds; MSRP: $8999.
Suzuki RMX450Z—weight without fuel: 263 pounds; MSRP: $8999.

In 2017 the bike returned sans illegal map. In every other way it was identical to the one from 2010. That included the throttle limiter. For the purposes of this test, that was replaced immediately with the one from the RMZ450 to allow full throttle. It must be said that this renders the bike illegal as a legitimate off-road bike, but, as we stated earlier, there are virtually no consequences to this other than making the bike perform properly. It’s still a very quiet bike, and it’s presumably more emissions-friendly than the carbureted Honda.
The Suzuki clearly has more peak power than the Honda, but the throttle response isn’t as good down low. This bike is a little more competition-oriented and likes to be ridden more aggressively. In fact, if you ride it at low rpm, it has a little hiccup and occasionally stalls. As the revs climb, it makes more power than the Honda, but it eventually goes flat on top too. Suzuki made it very easy to get a little more power if you want it. The airbox restrictor and the muffler’s inner baffle come out and give the bike more bang everywhere. Unlike on the Honda, the spark arrester stays in place when the baffle is removed. The side effects are that the bike gets louder and the low-rpm hiccup gets more noticeable. This sends you down a road where you need to modify the fuel map yourself. More on that later.

The main difference between the original RMX450Z and this one is that the EFI system is sealed and tamper-proof.

As you might expect from a Suzuki, the bike’s strongest asset is its cornering. The RMX might even be better in turns than the current RM-Z450 motocross bike. You can steer your way through a turn with the throttle shut—if that’s your style—or drift the rear wheel around, flat-track-style. It’s your choice. It does take a little muscle to do it all quickly, though, because the Suzuki has its own weight problem. On the trusty Dirt Bike scale, it weighs 263 pounds without fuel. You notice it when you try to go fast or stop fast. The Suzuki’s suspension deals with it well; the components aren’t that different from those on the Honda. In setup, though, the Suzuki is a little softer in front than it is in the rear. The bike has a little bit of a stink-bug attitude that makes it dive a little when you brake hard. Overall, though, it’s plush at both ends and good for trail riding at a moderate pace.

Yamaha based the WR450F on the 2016 YZ450F MX bike, but did more than give it electric start. The gearbox, power delivery and everything else were rethought for off-road.
Yamaha based the WR450F on the 2016 YZ450F MX bike, but did more than give it electric start. The gearbox, power delivery and everything else were rethought for off-road. The newest YZ450F is a different platform.

The Yamaha WR450F has been in the lineup for a long time, but this version is fairly new. It arrived in 2016 alongside the more competition-oriented YZ450FX, and both are based on the YZ450F motocross bike of the time. The YZ, of course, didn’t have electric start in 2016, but the two off-road bikes inherited almost everything else, including the reverse, rearward-tilting head. Offering two off-road bikes allowed Yamaha to be aggressive with the closed-course FX and offer a real trail bike in the EPA-compliant WR. The WR is a much better value than the FX because it has a headlight, an odometer and a radiator fan for only $100 more. If you want it to run like the FX, Yamaha offers a $114 Competition kit that includes a new black box for the ignition with programmable mapping. The reason that Yamaha can do that after Suzuki got busted is because the whole ignition is replaced; the one that comes on the bike is fixed and can’t be altered.

Yamaha WR450F—weight without fuel: 259 pounds; MSRP: $9099.
Yamaha WR450F—weight without fuel: 259 pounds; MSRP: $9099.

Like the Suzuki, the Yamaha comes with a throttle limiter and an exhaust inner baffle. We replaced the throttle limiter and left the baffle in place. The Yamaha is the most powerful of the three in this form, all baffles in place. It makes most of its power in the middle and actually revs out fairly high. Down low, the WR isn’t quite as responsive as the Honda, but it quickly catches up and pulls away in any horsepower contest. The WR is also clean and crisp down low. It doesn’t hesitate, cough or stall. Just as with the others, though, the peak horsepower is pretty tame for a 450. It’s hard to ride it and be satisfied when you know that more horsepower is locked up, trying to get out. As a side note, the WR’s gearbox works pretty well in stock form. First gear is very low, which is useful in many tight situations. If you unchain the beast with the Competition kit and perhaps a muffler, the bike becomes much more jerky down low. That renders first gear almost unusable. The power delivery is just too much, too fast.

The WR450F is similar to the YZ450FX, but fully compliant with off-road regulations.

The Yamaha chassis feels long compared to the others. It’s a big bike, although it weighs in at the exact same number as the Honda—259 pounds without fuel. You get used to it quickly and appreciate the bike’s stability at speed. The WR is set up for faster speeds than either of the others. The suspension is just a little stiffer, although still much softer than that of the FX or an MX bike. The Yamaha is also well balanced. Both ends seem like they were designed and tested by the same people with the same purpose in mind.

Any modifications that affect sound or emissions will make these bikes closed course vehicles. Right now, enforcement is strictly up to each state, even though the regulations are federal.

Any motor, mapping or exhaust modifications turn these bikes into closed-course, competition vehicles. The most difficult aspect of a test like this is comparing apples to apples. The Honda is the only bike that can be ridden in stock form; the others had to have the throttle limiters removed. That gives it a big head start right there, but even the CRF450X cries out for more mods once it’s out in the field. Luckily, it has been around so long that the road map to performance is easy. There are three things that most owners eventually do, but all three must be done together. When the stock pipe is replaced with an aftermarket system, the engine needs more air and more fuel. The first task is accomplished by cutting a larger opening in the airbox. There’s a fairly clear line to follow—just don’t overdo it. Then you need to rejet. The easiest way to go is to get an $80 JD Jetting kit. It comes with two needles, five main jets and a new air screw. The instructions give you a good baseline and clear troubleshooting directions. If you want to try the same thing with Honda parts, you can start with an NCYS needle in position three and a 165 main jet. You’ll probably have to make several trips into the carb to get it right. As for the air pump, you can leave it in place, but the bike will pop when you chop the throttle at high rpm. Applied Racing makes an air-pump removal kit that sells for around $40.
In the case of the Yamaha, the path is clear and even easier. The first stop is the GYTR Competition kit. It comes with mapping that works well for a YZ pipe, but even with a stock exhaust, the new ignition black box results in a big horsepower increase. If you get the Yamaha Power Tuner, you can dial it in for any specific pipe. The Power Tuner is a handheld EFI modification tool that works extremely well and sells for $300. It will not work with the stock ignition black box. As for intake modifications, the Yamaha doesn’t seem to need them. With the airbox mounted up high in front of the fuel tank, the bike breathes well and the filter doesn’t even get that dirty. You might try a lithium battery to save a few pounds, but the WR is already the only bike without a kickstarter.
Suzuki is gun-shy about offering any aftermarket parts for the RMX after the 2010 debacle. If you simply remove the airbox restrictor and the inner baffle, you end up with a fairly powerful bike. Some riders report that it doesn’t have any mapping issues in that configuration, but in our experience, the bike usually hesitates slightly. The easy remedy for that is to go with the JD EFI tuner. This is a piggyback device that modifies the signal between the bike’s central processor and the motor. It has a baseline setting that works well with the unbaffled exhaust and pretty much eliminates the hesitation. It also allows you to make fuel changes at specifically targeted rpm levels and/or throttle openings. It sells for $240.
With all three bikes modified as described, the pecking order doesn’t really change. The Yamaha is still the most powerful, and the Honda still has the best throttle response at low rpm. The one that benefits the most is the Suzuki, which is back in the game. Its power output is nearly on par with the Yamaha’s and is much less glitchy down low.

Going beyond simple modifications is a little pointless with these bikes. Their original appeal is that they’re trail bikes that are quieter and more friendly for casual riding without a checkered flag at the end of the day. It would be easy to lose sight of that and transform them into motocross bikes, step by step, and not very good ones at that. If you are looking for big horsepower, look elsewhere. If you are looking for a fun, quiet, reliable motorcycle that’s easy to ride and may even be eligible for a California green sticker, this is your stop. Of the three, the Yamaha emerges as the one bike that’s the most modern and the easiest to own. It works well in its mild, quiet configuration, and it’s the easiest to modify into something more. With all of these bikes, you have to know what you’re getting. From what we’ve seen, most buyers of new competition off-road 450s really want one of these. They just don’t know it.

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