2010 Kawasaki KX450F Comparison

Adam Waheed | January 1, 2010

Once again, there is no shortage of engine power with the 2010 Kawasaki KX450F.

Last year the Kawasaki KX450F wowed us with the audacious, yet manageable power of its fuel-injected engine, paired with a chassis adept at harnessing that power and putting it to the ground. While the bike isn’t exactly targeted for beginners, in the hands of a skilled pilot the big Kawi proved devastatingly fast and surprisingly rider-friendly.

After smoking the competition in last year’s 450 Motocross comparison we knew it was going to be tough to dethrone the returning champ. This year Kawasaki engineers made a few upgrades aimed at increasing durability, smoothing out the engine’s manners and improving mid-corner handling. We welcomed the changes during the 2010 Kawasaki KX450F First Ride and immediately recognized that Kawasaki again had something special in store for this year’s 450 shootout.

Like with the 2009 model, the crown jewel of the new KX is the engine. From the moment you twist the throttle there’s nothing to hide its immediate and forceful power delivery. With the throttle pinned the engine propels the rider forward in a way that the other bikes just can’t replicate. The dyno chart confirms our assessment from behind the helm. From just off idle until 7800 revs, the KX smokes everything. After that point the KTM bests it by a scant 0.4 ft-lb of engine torque. But keep the revs up and the Kawi engine again out paces the pack en route to a peak horsepower of 48.9 @ 8800 rpm. This allows it to retain the crown for outright horsepower. Not only is it the most powerful engine of the group it also has the loudest measured exhaust note (96 decibels), but our testers just couldn’t stop talking about the impressive powerplant.

Although it doesn’t steer as quickly as the CRF, the KX450F will surprise you with its low-speed agility.

“The Kawi felt like it had the gnarliest power. It’s the bike that’s easiest to get whisky throttle,” laughs McElroy. “It felt like a rocket. It would always want to wheelie… the thing is a beast.”
“The motor on that thing is unbelievable,” adds Armstrong. “Not only is it smooth, it also revs to the moon. But the best thing about its motor is you can be lazy and ride the bike in a taller gear, or you can ride it like a 250F and rev it really high. Either way it has plenty of power to pull in any gear.”
“The Kawasaki has the hard hitting motor monster of the group,” agreed Milan. “On tracks with ample traction, nothing can run with the Kawasaki. The power comes on strong right off the bottom through the arm stretching midrange and continues to pull strong even on top.”

Not only does the Kawasaki deliver the most amount of power, next to the electric-start KTM, it’s the easiest bike to start, requiring one or two kicks to fire. Although the Kawasaki’s five-speed transmission doesn’t feel like it meshes between gears a precisely as the rest of the bikes, it did perform without fault. We did notice a gap between second and third gears, but with such broad and robust power, it’s easy to work around. Kawasaki has the ability to run second gear longer, through a wider variety of terrain than the other bikes.

The KX450F’s engine cranks out so much power that it’s easy to overwhelm the rear Bridgestone tire.

“I could hold it in a gear longer than some of the other bikes down some of the longer straight-aways,” confirms Armstrong. “It’s just a bit more versatile no matter where you ride.”
In our third gear roll-on test, the Kawasaki aced the competition with a time of 8.21 seconds despite carrying the lowest 45.91 mph trap speed. This proves how potent its bottom-to-mid engine performance is. Conversely, in the holeshot test the Kawasaki took the longest time to get to Turn 1 (4.19 seconds), with the slowest 46.94 mph trap speed. This could be contributed to how aggressively it transmits power to the Bridgestone rear tire. Overpowering the available traction and causing wheelspin is an issue with the aggressive Kawi, so deft throttle and clutch operation is more critical on the starting gate. This is especially true considering that the clutch, while offering light lever pull, doesn’t supply as much feel as needed to maximize drive during aggressive race-style launches.
From the moment you lay eyes on the KX, there’s no hiding how big of a motorcycle it is. From the outright size of its engine to the broad perimeter of its aluminum frame and swingarm, everything on the KX appears oversized. So it isn’t much of a surprise that it is the heaviest motorcycle in this test, weighing in at 251 lbs. Subtract the weight of its 1.9-gallon fuel load, (second largest fuel capacity in class) and suddenly the Yamaha takes the honor of being the heaviest motorcycle, due to its smaller 1.6-gallon fuel capacity.
Despite its size, around the track the Kawasaki has surprising maneuverability. Clearly it isn’t as agile as the CRF, but it does change direction without much effort. While it steers heavier than some of the other bikes, it never turns more or less than what the rider asks of it. Once pitched into the corner the suspension offers terrific balance. Nonetheless, lighter riders noted that it was hard to get comfortable on the KX due to its stiffer suspension spring rates.

Despite being the heaviest motorcycle in this test (with weight of fuel), the KX450F can still be tossed around in the air.

“Out of all the bikes, the Kawi had the stiffest suspension so it was hard to get comfortable,” explains McElroy. “It never really worked right for me to ride it hard enough to get a good read. The one thing I could tell though is that it feels like it’s meant to be hauling ass. I just wish I could ride it with softer springs.”
Chipping in, Armstrong says, “Being that I only weight 155 lbs, the suspension on the bike was a little stiff, but we made some adjustments on both the compression and rebound which helped the bike sit down in the stroke more and feel more planted.”
The stiffer suspension spring rates clearly favor heavier, faster riders and permit the Kawasaki to ride much higher in the suspension stroke – a trait that many riders prefer. It will be most appreciated by aggressive racers who compete at very high-speed tracks.
“The stiffer spring rates on the Kawasaki were very confidence inspiring,” comments Milan, who is our tallest and heaviest test rider at 6-foot, 4-inches and 215 lbs. “Over-jumping or coming up short didn’t cause me as much panic, as the Kawasaki’s suspension handled it with ease.”

Through corner exit, some of the riders noted that it was more difficult to escape due to rear tire traction issues. Again this could be contributed to the engine’s blunt power delivery which simply overwhelms the capabilities of the Bridgestone M403 intermediate terrain tire.

Armstrong rated the KX450F’s ergonomics package the best.

At speed the Kawi’s chassis offers an exceptional level of stability. Whether blasting through the whoops or hauling around Racetown’s fast pot-holed sweepers, there are few obstacles that can upset the Kawasaki’s dependable chassis.

A well-sorted ergonomics package further aids the rider while maneuvering the KX. The seat isn’t nearly as slim as the ultra-narrow Honda but its extra girth will be appreciated by larger riders as it makes it easier for them to grip the bike with their legs thereby enhancing control. Like the Honda, the KX’s location of each control surface is well executed, albeit with an emphasis on taller pilots. The Renthal handlebar sits within a pair of reversible bar mounts. Below, oversized footpegs offer a large, secure platform, though still aren’t as wide as the massive Yamaha pegs.

“The Kawasaki is the biggest and most open-feeling bike in the shootout,” says an appreciative Milan. “It really works great for a taller rider. The only downside to the Kawasaki’s ergo package was the fact that it has the heaviest feel.”

My favorite thing about this bike is the ergonomics and how comfortable the bike feels,” agrees Armstrong, which is somewhat of a surprise considering his 5-foot, 7-inch stature. “From the second you sit on it, it just feels right. Everything from the seat, to the footpegs to the handlebar feels balanced.”

If you’re a skilled rider and know how to rip around the moto track at max speed, there’s no better bike than the 2010 Kawasaki KX450F.

The KX’s braking capabilities have more than enough power to slow you down from warp speed, but they lack a bit of feel as compared to the ultra-sensitive KTM’s and the Honda. Finding a different brake pad might be all it takes for a solution.

If you’re a larger, heavier rider, or really know how to put a motocross bike through its paces then the 2010 Kawasaki KX450F is the best 450 machine. The firm suspension offers excellent balance and is perfectly suited for high-speed tracks. While the Kawi certainly isn’t the easiest bike to ride in this quartet, in the hands of a skilled rider it absolutely shreds.


Adam Waheed

Road Test Editor | Articles | Adam's insatiable thirst for life is only surpassed by his monthly fuel bill. Whether rocketing on land, flying through the air, or jumping the seas, our Road Test Editor does it all and has the scars to prove it.

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