Kawasaki recently introduced its new 2011 Kawasaki KX450F at one of our favorite Southern California motocross tracks – Racetown 395. Now in its third year since a major overhaul in ’09, Team Green’s premium motocross bike gets another round of updates aimed at increasing performance and durability. The updates aren’t major, but that’s okay as the current generation KX is one of our favorite dirt bikes to ride and race.
Looks wise, the KX continues to resemble the race bikes piloted by the Kawasaki factory Supercross and motocross teams. For ’11 it’s dressed in an updated green/white/black graphics. Also new is the blue-anodized compression damping adjusters atop each fork leg and shock absorber, similar to the KX250F. Aside from those differences, the two-tone seat cover and black wheels appear the same.
Lift the KX off its stand and you’ll notice how heavy it feels at a standstill. Curb weight is virtually unchanged and comes in at 250 lbs. with a full 1.9 gallon tank of gas. Inside the plastic fuel cell, the fuel pump has been positioned at a different angle to help prevent damage as well as fuel starvation during long motos.
(Above) The 2011 KX450F sports an updated muffler claimed to produce less than 94 decibels. However on track the exhaust sounded as loud as the previous model. (Below) The 2011 KX450F gets blue-anodized compression adjusters atop each fork leg and shock just like the ’11 KX250F for a “factory” look.
Hop onto the seat and the bike feels tall, which is typical of the 450 Motocross class, and the KX-F in general, which is one of the larger offerings. The seat cover uses an updated texture on the side which is said to make it easier to grip between the rider’s legs. With the transmission in neutral, pull out the kick start lever and give it a firm, steady kick and the engine fires to life with zero fuss regardless of weather conditions or if the engine is hot or cold. In fact, the KX’s engine is so simple to start, we question why one would ever desire electric start. Pull the clutch lever, drop the shift lever down into first gear and it’s time to rip…
From the instant you roll out onto the track it’s surprising just how well the bike fits the rider. While it may not be as physically compact as other 450s, the spatial relationship between the Renthal handlebar, tacky seat and oversized foot pegs is sensible and will be appreciated by all but jockey-sized riders. This makes it comfortable for riders to maneuver while riding. Our only real complaint is the rock-hard hand grips which quickly give us blisters. Even worse is that they are almost impossible to replace due to the vulcanizing installation process from the factory.
The architecture of the fuel-injected and liquid-cooled 449cc Single is unchanged, however, inside it gets a reshaped piston designed to increase durability. The 12.5:1 compression ratio remains the same, but the ECU has been recalibrated providing a hotter, longer-lasting spark said to improve bottom end engine performance. Lastly, the EFI and ignition mapping has been altered to make the bike friendlier to ride.
Pin the throttle and the KX rockets forward as if you stabbed the imaginary turbo-boost button. Power comes on instantly with zero hesitation or bogging. It’s astounding how voracious the engine pulls as soon as the throttle is touched, even with the new EFI and ignition maps. Without a doubt the stock engine settings are still calibrated to a more experienced rider or racer. However those looking for a friendlier, or, conversely, even harder hitting powerband, then the fantastic Kawasaki Fuel-Injection Calibration Kit will interest you (see sidebar). Additionally the connection apparatus for the tool has been simplified and the fuel tank no longer has to be removed to install the kit.
Right off the bottom, engine power is so strong that it can easily overwhelm the grip capabilities of the fat 120-series Bridgestone tire. Fortunately, Racetown’s tacky ruts provide the traction to keep the rear tire hooked up and driving forward. The engine builds power smoothly across its rev range with zero perceived hit or step in power production. This allows the rider to hold a gear and rev the engine out to its 11,300 rpm redline or short-shift and ride the copious spread of instant torque. Either way the engine pumps out plenty of power to clear just about any obstacle you’ll encounter on the track, including Racetown’s gigantic 100-foot tabletop.
(Above) Once again, there is no shortage of power with the 2011 Kawasaki KX450F. (Center) The suspension continues to offer good balance making the bike easier to ride at the racetrack. (Bottom) Even though it’s no featherweight, the 250 lbs. KX450F is surprisingly maneuverable both on the ground and in the air.
Engine power is managed via a cable-actuated clutch and five-speed transmission that transfer force to the rear tire through 13/50 final drive gearing. Although we never encountered any problems with the gearbox, it too has received some upgrades. Specifically the tension on the shift spring has been increased and the position lever roller is larger in diameter which enhances gear engagement feel through the shift lever. The transmission certainly doesn’t feel like a “close-ratio” gearbox with noticeable spaces between second through fifth gears. However, due to the engine’s robust powerband and light, responsive clutch, the rider never feels like they are between gears.
One of the few complaints we had with the previous Kawi 450s was how loud the exhaust noise is and how the muffler sounds worn out after only a few rides. Engineers finally addressed it by fitting a new muffler can that’s claimed to keep noise under 94 dB. This is a full four decibels lower than we measured in our 2010 450 Motocross Shootout. Out on track the bike certainly didn’t sound any quieter, so we’ll have to wait until we sound test it for conclusive results.
This year’s model received some important chassis updates that significantly improved handling. Learn about these changes in the 2010 Kawasaki KX450F First Ride. For 2011, chassis upgrades were limited to the replacement of the aluminum engine mounts to those fabricated from steel. This small change was made to further optimize the flex characteristics of the chassis. Moreover, both the fork and shock have modified valving. The spring rates however are unchanged (0.48 kg/mm in the fork and 5.5 kg/mm on the shock).
In spite of its size and weight when rolling the KX450F will surprise you with its agility. The KX steers easily and predictably, never turning more or less than the rider inputs through the controls. Aim for an inside rut or shoot around the outside berm, either way, the Kawi’s chassis is flexible giving the rider options in a turn.
Once planted inside a rut the rear suspension allows the rear tire to track and it resists standing up or jumping offline, even if you’re not the most assertive with throttle application. Add some third or fourth gear speed and the KX’s chassis remains composed. While the front end does wiggle around, it’s within reason and can be cured by adding more rider sag which Kawasaki recommends being adjusted at 95 to 105mm. We ran it on the high side. It is important to note that even a few millimeter sag adjustment nets a difference in terms of handling attributes, so play around with setup in order to find out what works where you ride.
The suspension is calibrated for novice-to-intermediate riders in the 170-180 lb. range. For us this serves up the most optimum suspension performance for any stock 450. Generally the suspension felt balanced, though we did note that the fork lacks mid-stroke damping. We encountered the same issue with our ’10 model and eventually solved the issue by enlisting the assistance of RG3 Suspension during our Kawasaki KX450F Mammoth MX Race Project. Aside from that, initial damping, especially from the fork, feels supple and it has excellent bottom resistance at the
opposite end if you happen to overshoot a jump. The brakes also worked well delivering solid, fade-free power through the levers and an adequate amount of feel.
Although Kawasaki didn’t totally revamp its latest KX450F, there wasn’t reason to as the bike just plain works. Its ergonomics cater to the taller end of the rider spectrum and the engine and suspension settings favor faster and/or heavier riders. Yet the KX is a superb overall package and can be further customized to a person’s needs with the aforementioned fuel-injection kit. Factor in its outstanding Team Green amateur racing support program and that the MSRP only increased by $100 and you’ve got an ideal 450 machine to either race or play on.