Kawasaki didn’t leave a washer unturned with its prized motocrosser, the KX450, giving it a hydraulic clutch—a first for a Japanese-built motocross bike—an all-new motor with a new exhaust system and a redesigned valvetrain that features road-race-inspired finger followers. The 2021 Kawasaki KX450 also got a significantly updated chassis with a new coil-spring fork that replaced the previous pneumatic fork. But all that happened in 2019 when Kawasaki dropped the “F” in KX450F.
Since then, the KX450 has seen little changes. In fact, it didn’t get any updates at all in 2020 and only a few in 2021. But the changes that its Supercross championship-winning KX450 did get sound good to us and should make a difference on the track—for the better. Recently, Kawasaki gave us the keys to the 2021 KX450 to find out.
By Chris Siebenhaar
Photography by Kit Palmer
2021 Kawasaki KX450 Review | Good Memories
On the track, the new KX feels much as it did before—the chassis is nimble yet neutral; by that, I mean, while it turns well, it also is very stable and balanced. The bike doesn’t pitch excessively when under braking or acceleration, it remains stable in chop and doesn’t over react when encountering a hidden or ill-placed bump on the track.
The KX’s suspension is, in my opinion, one of the best out there. I’ve always been a big fan of the KX’s legs. Its Showa suspension is termed “A-Kit technology,” meaning it’s very similar to the suspension systems used by top-level race teams for years. While the A-Kit-inspired suspension might not be the exact $10,000-plus units on Adam Cianciarulo’s or Eli Tomac’s KX450, the stocker does share many of the same design features as theirs. I like the KX’s 49mm coil-spring fork because it is plush, yet still holds up very well when pushed through the stroke. In fact, I made only minor changes from the set baseline that we started out the day with, eventually settling on two clicks slower rebound and two clicks stiffer compression as the track got rougher. The Showa A-Kit shock is equally as versatile and impressive. With just a few minor adjustments, I got the back end to track well over acceleration chop and firmly planted while exiting corners.
I prefer a bike to steer with the rear, so for that reason, I ran 110mm sag versus the recommended 104mm and two clicks slower rebound. However, if you like the bike to pivot off the front wheel more, you should run the standard 104mm sag, and you’ll be rewarded with a very sharp-handling bike.
The KX450’s engine has been one of its strong suits for many years. The KX450 has never had what I would call a “weak” engine. In fact, I remember around 2010, Kawasaki actually detuned their engine because it was too aggressive. However, in the past few years, they seem to have found the sweet spot between powerful and controllable. The engine is potent—very potent—but still extremely manageable. Pair that with the included DFI couplers that give you a way to adjust power delivery, and you have an engine that will provide you with as much power as you need in the fashion that you desire. For engine fine-tuning, Kawasaki still relies on its $699.95 KX FI Calibration Kit accessory, which is insanely expensive compared to some of the other brands’ free tuning apps that you download to your smartphone.
2021 Kawasaki KX450 Review | What’s New?
Now for the new stuff. The 2021 Kawasaki KX450, which saw an increase of $100 over last year’s model, has a short list of changes: a new coned disc-spring hydraulic clutch, a new Belleville washer spring for the clutch, larger-diameter (139mm to 146mm) clutch plates with revised friction material, new dry-film lubricant coating on the piston skirt, and a new 1-1/8-inch Renthal Fatbar handlebar. All good stuff.
The big news here, however, is the clutch. Kawasaki thought outside the box and did away with the multi-spring pressure plates that have been used on MX bikes since day one. Instead, the KX450’s clutch now uses a cone, or cupped, disc spring instead of the previous five coil springs. Kawasaki isn’t the first to go in this direction. KTM uses a similar design that it calls Damped Diaphragm Steel (DDS) in some of its dirt bikes, but this is a first for a 450cc Japanese motocrosser. Did it pay off? Absolutely! Personally, I’ve never been a fan of hydraulic clutches due to their lack of engagement feel and modulation abilities. Hydraulic clutches typically have an on/off feel, so fanning, or feathering, the clutch when exiting a corner can be challenging to get the pull just right, especially when in the heat of a battle or fighting off arm pump.
To combat this, Kawasaki engineers redesigned every aspect of the clutch, even tackling how the plates separate from each other when you pull in the clutch lever. While this may seem trivial, if you have ever changed your own clutch, think of how hard plates stick to each other when covered in oil? Often times the suction is so strong you have to slide the plates sideways to pull them apart. Now think of trying to separate every fiber from every steel without the sliding, and all plates at once! It takes a lot of effort. Kawasaki redesigned the fibers to allow for easier separation, resulting in a lighter feel and smoother engagement.
The Belleville spring washer has a smoother and more progressive compression than traditional springs, again, allowing for an easier pull and smoother clutch action. All in all, this equates to a hydraulic clutch with the engagement feel of a traditional cable clutch, yet still has the soft pull of a hydraulic system. It really is the best of both worlds. And, this design has, in the past, shown to be more durable and consistent than the previous design. We’ll see after we get more time on the bike.
Besides the clutch, for performance Kawasaki applied a dry-film lubricant to the piston skirts. If I had ridden the 2020 and 2021 KX450s back to back, perhaps this addition could be felt, but drawing from memory, it seems the same. That’s not to say it’s pointless. Adding special coatings to these high-stress parts has been very common for years in all forms of racing, from MX to F1. Adding friction-reducing coatings to make the engine run more efficiently is fine with me, whether I feel it on the track or not.
Finally, there is the 1-1/8-inch Renthal Fatbar Handlebar. Compared to the previous crossbar-style handlebar, the non-crossbar Renthal Fatbar, which tapers to a larger diameter in the center, is actually much more forgiving and comfortable because there is now a certain amount of flex. And Fatbar does a better job absorbing vibration both from the engine and terrain.
The bars are shaped a little differently, too. The new bend lowers grip position 19mm and puts it 8mm closer to the rider, making it easier to weight the front wheel.
Regardless of bar-design preference, having a 1-1/8-inch handlebar standard means you have 1-1/8-inch clamps standard. Therefore, you can choose your style of handlebar without having to purchase aftermarket bar clamps. The KX’s clamps are still reversible, giving you 35mm range of adjustment—front to back—via four bar positions. Footpeg height is still adjustable, as well.
So, after getting a total rebuild in 2019, the KX450 gets its first update since, and so far we’ve liked what we’ve seen, or should we now say felt. Getting a re-vamped clutch and new handlebars might not seem like a whole lot, but I can confidently say that these two seemingly “small” upgrades do indeed make an already outstanding motorcycle even better. CN
2021 Kawasaki KX450 Specifications
||4-stroke, liquid-cooled, DOHC, 4-valve, single
|Bore & Stroke:
||96.0 x 62.1mm
||DFI w/Keihin 44mm throttle body
|Rake / Trail:
||27.6° / 4.8 in.
||Showa 49mm inverted coil-spring fork, fully adjustable, w A-Kit Technology
||Uni-Trak, Showa single shock, fully adjustable
|Front Tire Size:
|Rear Tire Size:
||Single 270mm petal disc, 2-piston, Braking
||Single 250mm petal disc, 1-piston, Braking
||1-1/8-in. Renthal aluminum Fatbar
|Weight (dry, claimed):
|Weight (wet, claimed):