INSIDE MXA'S 2009 KAWASAKI KX450F TEST
Ever since the Kawasaki KX450F was first introduced, it had the makings of an omnipotent motocross machine. But, in the opinion of the MXA test riders, it always came up wanting in several key areas. Need examples?
Kawasaki Motorcycle test
2006 KX450F: It had a mellow engine that was pleasantly powerful, but tended to rev up slowly. The deal-breakers were the four-speed tranny (that was really only a three-speed), wallowy rear suspension, harsh Kayaba AOSS forks, and a nagging tendency to stand up in the center of the corners.
2007 KX450F: For 2007, Kawasaki pumped up the engine by three full horsepower, fixed the forks, and added a fifth gear. Unfortunately, the five-speed gearbox was no better than the old four-speed box, because all Kawasaki did was add a fifth gear on top. Additionally, the rear suspension was still wallowy and the handling still didn't like corners.
2008 KX450F: In a strange move, Kawasaki gave back most of the three horsepower it gained in 2007. With less bark, the engine became more manageable, but not faster. With stiffer valving front and rear, the suspension was improved, but the handling didn't win any converts.
Which leads the MXA wrecking crew to the 2009 Kawasaki KX450F.
Q: WHAT DID KAWASAKI CHANGE ON THE 2009 KX450F?
A: Kawasaki's engineers comprehensively redesigned virtually every part of the 2009 KX450F with a new fuel-injected engine, refined aluminum chassis, all-new plastic, and extensive durability enhancements. This is a totally different bike from the original 2006 model.
Q: HOW DOES KAWASAKI'S FUEL INJECTION COMPARE TO THE EFI ON THE CRF450 AND RM-Z450?
A: Favorably. The MXA test crew can take fuel injection or leave it. Why are we so cavalier? Mostly because the benefits of fuel injection don't seem to pay off in performance. Yes, fuel injection eliminates jetting issues, but apart from throttle response, it hasn't shown any great proclivity to increase peak horsepower. Take the 2009 fuel-injected CRF450; it is down two horsepower and gave up power over the top to the Keihin-carbed 2008 CRF450. Suzuki's fuel-injected bike runs well, up to a point, but unfortunately, when it reaches that point, which is a lowly 10,000 rpm, it dies in its tracks.
Hallelujah! Kawasaki has built a fuel-injected engine that didn't give up power, over-rev or top-end. The 2009 fuel-injected KX450F has one horse more at 8000 rpm, three horses more at 9000 rpm, three horses more at 10,000 rpm and three more at 11,000. Peak horsepower on the 2009 is 52.3 horsepower at 9000 rpm (the 2008 model only made 50.5 horsepower at 8500).
Kudos to Kawasaki—they got fuel injection right!
Q: HOW DOES KAWASAKI'S FUEL INJECTION DIFFER FROM SUZUKI'S AND HONDA'S?
A: Although fuel injection is new to motocross bikes, it is old hat in the automotive and street bike biz. And, while it may seem high-tech, motocross fuel injection is simplistic. It mimics the installation, sensors and computing power of a 1991 Subaru Justy (the 1990 Justy was the last carburated car sold in America).
How does Kawasaki’s fuel injection differ from the systems used by Honda and Suzuki? Here is the list.
(1) The CRF450's throttle body is 50mm; Kawasaki and Suzuki have 43mm throttle bodies.
(2) Honda and Kawasaki use 50 psi fuel line pressure; Suzuki uses 42 psi.
(3) Honda and Kawasaki both offer optional software and plug-in programmers for around $350 that allow the fuel injection system to be altered.
(4) All three bikes have their fuel pumps in the gas tank, but Kawasaki and Honda use rotationally molded plastic gas tanks, while Suzuki uses an aluminum tank. Fuel capacity on the Kawasaki is 1.8 gallons (1.5 on the CRF450 and 1.6 on the RM-Z450).
(5) Thanks to the broader powerband, higher idle setting and heavier flywheels, we suffered fewer episodes of flame-out on the KX450F than on the RM-Z450 or CRF450.
Q: HOW FAST IS THE 2009 KX450F?
A: This is an awesome engine. The KX450F is strong off the bottom without being jerky (unlike the CRF450—which hits too hard off idle). The KX450F builds power up and over the midrange with a strong, broad and steady pull (unlike the RM-Z450, which signs off too quickly). The KX450F makes the most peak horsepower of any Japanese 450 (unlike the Yamaha YZ450F—which, thanks to its goofy muffler, makes the least).
When compared head-to-head against the all-powerful KTM 450SXF, the KX450F makes more power from idle to 7000 rpm and the KTM makes more power from 8000 rpm to sign-off. The horsepower difference is about the same for each bike at each end of the spectrum.
Q: IS THE 2009 KX450F FASTER THAN THE 2008 KX450F?
A: Yes. It's a close relative to the very strong 2007 KX450F engine.
Q: IS THE KAWASAKI KX450F POWERBAND THE BEST IN THE CLASS?
A: For riders who like low-to-mid engines (that pull over the top), the KX450F powerband is the cat's meow. Its only real competitor in the 2009 sweepstakes is the mid-and-up KTM 450SXF powerband, which trades low-end power for abundant top end.
There is a caveat. The KX450F has a great engine and awesome powerband, but an atrocious transmission. It's geared too tall, the gaps between the gears are big enough to drive an Airstream trailer through, and the shifting is not confidence-inspiring. In short, the great powerband is transmitted to the ground through a seriously flawed transmission. Sadly, the gappy tranny dilutes the KX450F's great powerband.
Q: WHAT DID KAWASAKI CHANGE ON THE 2009 ENGINE?
A: Apart from the obvious Keihin fuel injection system, Kawasaki made eight major changes to the powerplant.
(1) Engine size. The new engine is more compact (from 105mm tall to 100mm tall) and lighter. Additionally, the engine is angled three degrees forward in the chassis.
(2) Piston. The coated, forged piston has a reshaped crown that raises the engine's compression ratio from 12.0 to 12.5:1.
(3) Exhaust. The one-piece titanium head pipe is tapered from 35mm to 45mm. The larger-volume muffler uses long-fiber packing that lasts longer and extends
(4) Valves. The 36mm intake and 31mm exhaust valves are titanium with aluminum spring retainers to reduce reciprocating weight. The intake valves are made from a higher-strength material with finer metal grain for 50 percent greater resistance to fatigue.
(5) Generator. Traction has been improved with increased rotational inertia via a larger diameter AC Generator rotor.
(6) Crankshaft. Revised webbing on the crank significantly increases crankshaft balance (important considering the increased inertia of the larger diameter AC Generator rotor). The crankshaft balance factor is 60 percent.
(7) Radiators. The 6.4mm wider radiators hold six percent more water. To help even more, the radiator cores are tighter with new finning, the radiator’s louvers have been increased from three to four, and the water jacket routes the coolant to the front of the cylinder head (where most of the heat is).
(8) Oil capacity. The amount of oil in the engine has been reduced from 1500cc to 1300cc.
Q: WHAT WAS KAWASAKI TRYING TO FIX FOR 2009?
A: Kawasaki's engineers knew exactly what needed fixing on the 2009 KX450F—and horsepower, jetting and carburetion weren't at the top of the list. The big goals for Kawasaki were (1) handling, (2) rear suspension, (3) transmission ratios and (4) ergonomics.
Q: WHAT DID KAWASAKI DO TO THE 2009 KX450F CHASSIS?
A: An incredible number of changes went into the 2009 frame. Here is the list:
(1) Weight. The 2009 frame is 2.2 pounds lighter.
(2) Spars. The main spars are now 69mm by 24mm (last year the dimensions were 70x27).
(3) Tubes. The steerer tube and down tube have been reshaped, redesigned and lightened.
(4) Subframe. The subframe has been strengthened, especially at the pipe mounts, but is lighter thanks to larger-diameter but thinner-walled tubing. It is also 6mm narrower and 1.3 pounds lighter.
(5) Swingarm. A new D-shaped cross section design is 5mm taller at the front (74mm to 79mm) and 2mm shorter at the rear (from 60mm to 58mm).
(6) Swingarm pivot. Kawasaki raised the swingarm pivot 3mm higher on the chassis.
(7) Head angle. The 2009 KX450F is 26.7 degrees. The CRF450 is 26.52, Yamaha is 26.9, KTM is 26.5 and Suzuki 25.30. Rated in terms from steep to slack, the RM-Z450 is at least 1.2 degrees steeper than any other bike, followed by KTM, Honda, Kawasaki and Yamaha.
(8) Fork offset. Previous KX450F fork offset was 24mm. For 2009, it has been reduced to 23mm.
(9) Shock linkage. The rising rate was changed to make it stiffer in the initial part of the stroke.
Q: WHAT ARE THE MOST IMPORTANT FRAME CHANGES?
A: All of Kawasaki's frame changes offer advantages, but the two that strike a chord with the MXA wrecking crew are the 3mm higher swingarm pivot and 23mm fork offset. Here is why.
Swingarm pivot. Motorcycles produce a hidden force called chain torque. It is a byproduct of the relationship of the countershaft sprocket, swingarm pivot and chain line when force is applied by acceleration. Chain torque has the power to jack the rear suspension up under acceleration or pull it down. Historically, only Eyvind Boyesen and Horst Leitner have successfully addressed the negative effects of chain torque on a bike's rear suspension. But for 2009, Kawasaki made an effort to feed more chain torque into the 2009 KX450F chassis. Why? Because Kawasaki wanted chain torque to help keep the rear of the KX450F from wallowing under acceleration (this was also aided by the stiffer initial rising rate linkage). Harnessing chain torque is a double-edged sword, but Kawasaki's motive was good.
Fork offset. Every hardcore KX-F rider runs 22mm offset triple clamps (and that includes Team Kawasaki's most famous riders), so it was kind of strange that Kawasaki's engineers chose to swap from 24mm to 23mm for 2009. As we discovered with the 2009 KX250F, going halfway to the race-proven offset is like taking half an aspirin for a headache. It feels a little better, but it isn't relief.
Q: HOW DOES THE 2009 KX450F HANDLE?
A: If Kawasaki wants to build a great handling bike, they are going to have to take more chances. That may sound strange considering that they totally redesigned the 2009 KX450F. The catch is that they could have saved themselves the trouble. For all the KX engineers’ frame mods, geometry changes, offset shifts and chain torque variations, all the handling quirks of the 2008 KX450F are still there. It's all new, yet it is still the same.
The 2009 KX450F is a milquetoast chassis. It has a slack head angle, jumbo-sized ergos and a heavy feel. Kawasaki's engineers need to commit to a program that includes a steeper head angle, shorter wheelbase, lower seat height, more ergonomic riding position and miniaturization of everything that doesn't move. Until then, the KX450F will maintain the same cranky character that its brethren have displayed since 2006.
Q: WHAT IS THE DEFINING CHARACTERISTIC OF THE KX450F CHASSIS?
A: What is the KX450F’s character? In our opinion, the KX450F is a big runaway train of a bike. It's tall, long and wide. It wants to turn, but hesitates in the center of corners and twitches momentarily. Riders get the sensation that the bike is trying to stand up, but in reality the front of the bike has reached a point where the rear must follow—and it refuses. The outcome is a rocking motion of the chassis. There is a lot of fore-and-aft movement that causes the geometry to be in flux at the moment when you want it to be fixed. You want it to turn, but it wants to think about it for a little bit longer.
Q: WHAT CHANGES WOULD WE MAKE TO THE 2009 KX450F CHASSIS?
A: The 2009 KX450F can be improved. All it takes is a checkbook.
Handling. We want 22mm offset triple clamps. Hard to believe that one silly millimeter would make a difference, but it does.
Gearing. The tranny has big gaps between first, second, third and fourth gears (remnants of the fact that it is a four-speed gearbox with an extra gear on top). The poor man's gearbox fix is to add one tooth to the rear sprocket (51 teeth instead of the stock 50). That brings second gear down, moves third gear closer, and lessens the gap between third and fourth.
Linkage. We believe in the Pro Circuit shock linkage. It stiffens the initial part of the stroke even more than Kawasaki's increased chain torque and new link curve.
Q: WHAT WERE OUR BEST FORK SETTINGS?
A: We liked Kawasaki's Kayaba AOSS forks. At first we thought that we were going to have trouble with them because they were so stiff that we had to turn the compression clicker all the way out. Surprise! As they wore in, we discovered that the Kayabas came into their own. For most test riders, the spring rates were ballpark. And, the plus of having the adjusters turned out was that we could turn them in as the forks wore in. For hardcore racing, these are MXA’s recommended 2009 Kawasaki KX450F fork settings:
Spring rate: 0.47 kg/mm
Oil height: 340cc
Compression: 18 clicks out
Rebound: Ten clicks out
Fork leg height: 5mm up
Notes: We had to change the clicks as the suspension broke in. Of course, changing the shock linkage and fork offset made slight differences in the compression strokes.
Q:WHAT WAS OUR BEST SHOCK SETTING?
A: Remember when we told you that Kawasaki raised the swingarm pivot? Sure you do. It was a technologically smart move in the battle to stop the KX450F from wallowing. The additional chain torque holds the shock higher in its stroke longer. For hardcore racing, these are MXA’s recommended 2009 KX450F shock settings:
Spring rate: 5.5 kg/mm
Race sag: 100mm
High-compression: One turn out
Low-compression: Eight clicks out
Rebound: Eight clicks out
Notes: The 2009 KX450F is very sensitive to balance between the front and rear. In the past, we used an aftermarket Pro Circuit linkage to hold the bike in a more consistent position. For 2009, we think it still needs the linkage.
Q: WHAT DID WE HATE?
A: The hate list:
(1) Shifting. Maybe it shifts better than it did a few years ago, but that isn't a compliment.
(2) Gearing. The quick fix is one tooth on the rear.
(3) Front tire. Kawasaki must have gone to the vintage museum to spec the less-than-spectacular Dunlop D742F front tire. This isn't even the newer D742FA, but the old, disgraced 742F.
(4) Overheating. We boiled it in long GP-length races. We sought advice from Kawasaki mechanics and they said to switch the 1.3 kg/cm2 radiator cap for a 1.8 (that's what the team runs). The Kawasaki part number is 49085-1077. A 1.8 kg/cm2 equals 25.6 psi. The stock 1.3 cap is 18.5 psi. A radiator cap will not raise or lower your engine's temperature, but it does raise the boiling point by three degrees per pound of pressure.
(5) Sound. The KX450F is the winner (if by winner you mean the bike with the loudest production muffler). At 99dB, the KX450F wouldn't pass last year's AMA sound limit, let alone 2009's 94dB standard. The KTM 450SXF (95.4dB), RM-Z450 (95.5dB), YZ450F (98dB) and CRF450 (97dB) were quieter at the AMA's new 4500 rpm sound test level.
(6) Transmission. We don't want a totally new gearbox; just give us the same close-ratio unit that Bubba ran this year.
(7) Graphics. Can you help us look for them? We think they fell off on the back straight.
(8) Chain guide. Kawasaki made it smaller, but it still doesn't last long enough to get attached to.
(9) Size. Paul Bunyan would fit perfectly. It's big, and in places where it’s not all that large, it feels big.
(10) Rear fender bolts. The two bolts on the underside of the rear fender, up by the airbox, are magic. They can disappear.
(11) Weight. Kawasaki's claimed curb weight is 247.2 pounds, Which would make their dry weight in the high 230’s.
Q: WHAT DID WE LIKE?
A: The like list:
(1) Powerband. The best fuel-injected powerband around (and it's not dog meat by carburated
(2) Footpegs. They were 46mm; now they are 50mm. Do I hear 51?
(3) Jetting. There is no jetting.
(4) Programmer. Kawasaki offers an ECU programmer tool that can reprogram the data maps or record up to six hours of rpm and throttle position settings.
Q: WHAT DO WE REALLY THINK?
A: The KX450F's powerband is easily the best part of the bike. But—and the list of buts is rather long—the transmission ratios are wrong...the shifting is spotty…the cornering is cranky…the layout is jumbo-sized…and the muffler is loud. Maybe it's just us, but the engine had us dreaming about what might have been. Reality was something quite different.