2009 Kawasaki KX450F First Ride

MotorcycleUSA Staff | September 22, 2008

The all-new KX450F only costs  550 more than the 2008 model it replaces. MSRP is now  7549.
Engine: 449cc liquid-cooled Single, DOHC, 4-valves
Bore x Stroke: 96 x 62.1mm
Compression Ratio: 12.5:1
Fuel Delivery: Fuel-Injection
Transmission: 5-Speed
Front Suspension: Kayaba AOS 48mm fork, 22-position compression and 20-position rebound damping adjustment, 12.4 in. travel
Rear Suspension: Kayaba shock, 22-position low-speed and stepless high-speed compression damping, 22-position rebound damping and adjustable spring preload, 12.4 in. travel
Tires: Dunlop D742 90/100-21, D756 120/80-19
Curb Weight: 247.2 lbs. (claimed)
Wheelbase: 58.3 in. Length: 86.0 in. Width: 32.3 in.
Ground Clearance: 13.4 in.
Seat Height: 38.0 in.
Fuel Tank Size: 1.8 gal.
MSRP: $7549 Lime Green, $7749 Monster Energy

Slow, sluggish, lethargic. These are words that you’ll never hear by a rider at the controls of Kawasaki’s new KX450F. To say that Kawi’s 450F is quick is like saying that you’re neighbor’s blown ’68 Chevy Nova has decent get-up-and-go. And although outright power and sheer acceleration force are a substantial part of the new KX-F package, there are plenty of other tweaks that enable you to put that power down to the dirt and get around the track more easily than ever.

With the arrival of the 2009 model, Kawasaki marks its second-generation KX450F. And this in fact is a major overhaul with changes to the engine, fueling system, exhaust, chassis and bodywork. Despite its resemblance to last year’s machine, there really aren’t many parts carried over, with the exception of wheels, brakes and tires.
Visually, the KX-F wears new body panels with the shrouds and side plates being made from dual injection-molded plastic. This allows multiple colors (green, black and white) to be used on a single plastic piece. Also new is the seat, which complements the slimmer chassis (more on that later).

Beneath the green skin is a new 449cc liquid-cooled Single. Bore/stroke figures are unchanged, though a new piston bumps compression up to 12:5:1 (from 12.0:1). The engine’s top-end received quite a bit of TLC by Kawi engineers with the result being a 5mm shortened cylinder head (down to 100mm). Inside, the intake and exhaust ports have been revised. Also new are the 36mm titanium intake valves, said to be more durable for increased engine life.

A new crankshaft graces the bottom-end. Despite the use of a larger AC generator rotor required to meet the additional power demands of the fuel-injection system, crankshaft rotational inertia and balance remains the same as this year. A new crankshaft large bearing and 2mm longer connecting-rod roller bearings are also used and said to increase engine durability. Another durability enhancement is the updated piston-cooling oil jet.

A single, 12-hole fuel-injector (off of a 2007 Ninja ZX-10R sportbike), replaces last years 40mm Keihin carburetor and injects fuel at a 45-degree angle into the 43mm throttle body. The setup is designed to work in conjecture with the revised cylinder head porting and boosts midrange power. A double throttle linkage on the throttle body itself allows it to open faster after 3/8 input. An easy-to-access fast-idle knob is also employed and increases engine rpm when starting in colder conditions.

This is the optional KX-FI calibration tool that attaches atop the ECU. It give you the ability to tune the fuel and ignition maps on your KX-F as well as store and view up to six hours of riding data.
This is the optional KX-FI calibration tool that attaches atop the ECU. It give you the ability to tune the fuel and ignition maps on your KX-F as well as store and view up to six hours of riding data.

Controlling the EFI setup is an ECU located behind the front numberplate. As soon as the kick-start lever moves power is generated and transferred to the ECU, in-tank aluminum fuel pump, and fuel-injector. Gone is the handlebar mounted hot-start/compression release, which is now completely integrated, ensuring that engine starting is a quick and painless affair hot or cold.

An optional KX-FI calibration tool (price TBD, but expect less than $500) allows the user to select between seven pre-programmed fuel and ignition maps (hard surface, soft terrain, leaner, richer, advanced/retarded ignition and beginner-rider setting) or you can create your own fuel map; say for an aftermarket exhaust or race fuel via its 3D computer interface. Another feature of the tool is the ability to log up to six hours of real-time data sampled every 1/10th of a second! Data channels consist of air/coolant temperature, engine RPM, throttle angle, manifold pressure, ignition timing, fuel adjustment, gear position and voltage. To put things in perspective, this is the same kind of technology you get on a $20,000 Ducati 1098S sportbike. Although we didn’t get a chance to play with it this time around, we look forward to testing it in the next few months.

Purging spent fuel is now handled by a longer one-piece titanium header that snakes back into a new aluminum muffler body with increased noise silencing capabilities.

New radiators look like there were pulled off Tim Ferry’s No. 15 race bike and use a tighter core/fin design. Reshaped plastic louvers deliver more air-flow and both radiators are manufactured with a reinforced design making them less susceptible to damage in an inevitable crash.

Complementing the changes under the hood is an extensively modified chassis. One of the complaints some of our testers had about the ’08 KX450F was how wide it felt as compared to the others in its class. So, engineers trimmed the main frame by 6mm side-to-side and 2mm in height. The steering head has also been slimmed down and the engine has been tilted forward by three degrees in order to put more weight on the front tire. An updated subframe makes use of larger diameter aluminum tubing and now uses only one bracket to hold the exhaust and rear fender as opposed to two. The subframe also has a wider top mounting area which is supposed to increase overall rigidity. Lastly, wider footpegs are employed (from 46mm to 50mm) and attach to the frame via a mounting bracket which helps eliminate packing of dirt between the frame and the footpegs.

Although the high level of grip provided by Muddy Creek s tacky soil certainly assisted rear wheel traction  the smooth power delivery and complaint rear suspension really gets the bike off the corner in a hurry.
Although the high level of grip provided by Muddy Creek’s tacky soil certainly assisted rear wheel traction, the smooth power delivery and complaint rear suspension really gets the bike off the corner in a hurry.

The aluminum swingarm mounts to the frame 3mm higher and features a new cross bracket (metal area between rear wheel and shock body) and a more tapered shape that’s 5mm taller in the front (from 74mm) and tapers back to its 2mm shorter tail (from 60mm). Kawasaki claims the end result of the changes are improved traction and stability. 

Just like the previous model, Kayaba suspension graces the bike on both ends. Up front the 48mm AOS (Air-Oil-Separate) fork sits in a reshaped upper triple clamp with slightly less offset (from 24mm to 23mm) for sharper steering. Underneath the large black fork guards, a fresh DLC (diamond-like-coating) on the lower tubes and a new Kashima inner coating reduce stiction and improve fork action. Revised damping characteristics complement the fork changes.

Rounding out the changes for ’09, a reworked Kayaba shock still features 4-way adjustability but now uses a larger 50mm piston (previously 46mm). Just like the fork, an ultra-slick Kashima coating is used for freer flowing action.

To find out if Kawasaki’s engineers did in fact improve the KX450F we spun some laps around the legendary Muddy Creek Raceway in northeastern Tennessee.

Hopping aboard the new KX-F for the first time reveals a slightly slimmer machine. The change isn’t dramatic yet it’s still noticeable. Despite its slightly more compact size, it would seem that the Kawasaki’s 450F will still be the preferred choice for larger sized riders as surmised by our 6’4″ 210 lbs. intermediate test rider, Bret Milan.

“Due to my height, some bikes feel really cramped and uncomfortable to ride in the standing position,” said Milan. “However, the KX450 has a very roomy cockpit. The larger footpegs make landing from big jumps more comfortable as well. Another plus is that the stock Renthal bars aren’t too low and are well matched to the bike’s total ergonomic package.”

Suspension compliance and balance has also been significantly improved. Specifically action through the entire stroke was far more responsive than the  08 machine.
Suspension compliance and balance has also been significantly improved. Specifically action through the entire stroke was far more responsive than the ’08 machine.

Even the latest 4-stroke MX’ers have a reputation for difficult starting, but we’re pleased to report that Kawasaki has managed to completely erase that trait. Starting the bike, whether the engine is cold or hot, is as easy as one or two kicks. Just to be sure, I took a spill (in the name of testing of course) and sure enough two kicks and I was running again.

Sometimes the use of fuel-injection can dull down the engine’s character and take away from the thrill of acceleration, but rest assured when you’re on this machine you definitely know that it’s a Kawasaki. From the second you twist the throttle grip it’s impressive how instantly the power comes on. Although its hard to tell without riding them back-to-back this years KX-F definitely feels faster. You can literally wack the throttle from just off idle and the bike lunges forward without any type of lag or hesitation. It’s like your right wrist has a direct connection to the Dunlop rear tire.

“It pulls much better right off the bottom as compared to my ’08,” said our tester Milan, who currently has the older model in his garage. “I had to install a smaller pilot jet to get the low-end ‘pull’ that I was looking for, but the motor on the new bike was absolutely electric! It pulled evenly from the bottom to the top with no cough or hesitation anywhere.”

Kawasaki’s 450F mill has always had a propensity to build revs quickly, but this one spools up faster than ever and it does so in a manner that is completely linear and devoid of any power hit whatsoever.

“It gets to the top really quick,” commented Milan. “Over-rev was great too, but since the bike pulled so well off the bottom, I rarely found myself even utilizing the upper reaches of the rev range. I would simply up-shift and keep accelerating.”

Metering engine power is far more precise then before. In fact, throttle response is so exact that for some it will border on being too sensitive. Therefore some patience is required while the right hand gets acclimated. A trick for less experienced riders is to run the bike in a higher gear, that way if you get sloppy with the gas you won’t be in the meat of the powerband and it’ll be a little more difficult for the bike to get away from you.

Under hard acceleration the exhaust note coming out of the aluminum muffler is still pretty raspy, but it’s not as loud and rickety sounding as the ’08.

As you can see the 48mm Kayaba AOS fork has excellent bottoming resistance despite our testers 210-lbs weight.
As you can see the 48mm Kayaba AOS fork has excellent bottoming resistance despite our testers 210-lbs weight.

On last year’s test bike our riders could be heard complaining about the transmission, but on this year’s machine the 5-speed transmission performed flawlessly. Overall gearing felt a bit on the tall side, but it’s almost a mute point as the engine is so versatile that it can pull in a high gear without any coughing or sputtering.

Pointing the KX-F into the corner–especially a corner with a deep rut–is far easier then before. Where last year’s bike would, at times, want to plow up and over ruts, this machine feels like it has some kind of sophisticated NASA-based earth radar which actively seeks ruts out.

“This front tire felt way more planted,” said Milan after putting in a 20-minute moto. “My old bike would push the front-end slightly and required careful body position to make the front tire stick. This bike really carves corners quite a bit better. Best of all, Kawasaki never gave up any stability to accomplish this. I didn’t notice any headshake at all.”

Getting out of the corner was equally as rewarding. Although the level of grip provided by Muddy Creek’s tacky soil certainly assisted rear wheel traction, the smooth power delivery and compliant rear suspension seemed to have a synergistic effect, allowing the rider to obtain spectacular drives through corner exit with ease.

Suspension compliance and balance has also been significantly improved. Although the spring rates seemed a little bit on the stiff side for novice levels, action through the entire suspension stroke was responsive. Another plus is the wide-range of suspension adjustment. Switching suspension settings back and forth for my 180-pound weight and our tester’s 210-pound weight wasn’t at all an issue.

“Due to my size, I’m seldom impressed with stock suspension as it’s usually too soft for me. And although I would definitely need to install stiffer springs if it was my bike, the valving was right in the ball park for me with excellent bottoming resistance,” Milan said, summing things up.

After a full day of flogging Kawi’s new big-bore MX’er, we came away impressed. And it isn’t because of its fast, easy-to-use engine, or its comfortable, well-sorted chassis. It’s because it does all of those things in unison, like a well-practiced orchestra, which allows the rider to put in lap after lap in a safer, more controlled way than ever.

Let us know what you think about the 2009 Kawasaki KX450F in the MotoUSA Forum.

MotorcycleUSA Staff