2006 Kawasaki KX450F Test on Motorsports-Network.com

MN Test - Kawasaki 2006 KX450F
The wait is over, Kawasaki's large bore motocrosser is finally here!

The long wait is over. Kawasaki teased us with the pending release of the KX450F last season – but it didn’t happen. The company

decided the bike wasn’t quite up to the standards they had set, so they delayed the bikes release until the 2006 model year. Who could blame them, as they were jumping into the second most highly competitive arena in motorcycles, only the fierce battle for building the best 4-stroke 250 motocrosser is more fiercely contested. This delay gave Kawasaki even more time to get it right, which means the 450F has been through numerous development generations before ever being released to the eager riding public.

What Kawasaki settled on is a 4-speed, 449cc, 4-valve, DOHC liquid-cooled four-stroke powered machine. The titanium valves (36mm intake, 31mm exhaust) are held up with double springs and feature aluminum valve retainers to reduce reciprocating weight. The intake ports are said to be hand-finished to improve intake efficiency. A screw-type cam chain tensioner is used; the piston is covered wit a low-friction material.

An auto decompression system and a hot-start system with a bar mounted lever are used to ease starting. The exhaust header, as well

as the heat shield, are made of titanium. The narrow radiators are new units with more tightly packed cores for better heat dispersion. The narrow aluminum perimeter frame is made from forged, extruded and cast pieces. Footpegs and footpeg brackets are made from light-weight titanium. A small aluminum skid plate sits between the bottom frame rails.

Suspension duties are handled by a 48mm inverted Kayaba fork which keeps oil and air in separate chambers for stable performance; the fully adjustable rear shock attaches to a Uni-Trak linkage system. Suspension travel is 12.4 inches front and rear.

The 220 pound (claimed) KX450F carries 1.9 gals. of fuel, has a 58.5 in. wheelbase, a tall 38.0 in. seat height and a ground clearance of 13.6 ins. The big KX rolls on 80/100-21 in. and 100/90-19 in. rubber. MSRP is $6,799.

You’d think with the rumblings over Suzuki’s 450 being a 4-speed and Yamaha’s actually switching their YZ450F

back to a 5-speed to meet consumer demand that there'd be no way Kawasaki would even consider releasing the bike as a 4-speed (they tested both 4-speed and 5-speed versions of the bike extensively) – but they did. We were told that after extensive track testing they found that test riders were never using 5^th gear. Our personal guess is that Japan dictated the 4-speed setup, as Kawasaki has many dedicated and knowledgeable people in the US who we believe would have cast their vote for a 5-speed. The result is a bike that will be just fine on most tighter tracks, but for open terrain tracks and GPs you’ll find yourself looking for more cogs. With that said, we can’t argue with Kawasaki’s and Destry Abbott's results in off-road racing with the machine. We were told these bikes are just running higher gearing. James Stewart is said to have run a four-speed all season - but he has an entire crew to change his gearing as often as needed.

With all this said, there’s no denying the KX450F is one exciting motorcycle – and we were bursting at the seams to jump aboard the machine. Our first ride was at Southern California’s Elsinore Vet track. The first thing we noticed is the bike’s got tons of power, stump pulling and surprisingly useable power. Tied to a 4-speed gearbox, this means you won't have to shift the bike nearly as often, leaving you with more time to worry about attacking the track. You'll want to avoid using first gear, however, as it simply slows you down too much. We actually had to keep reminding ourselves not to shift so often.

Like other Kawasaki motocross models we’ve ridden recently, we had to make some small adjustments to the suspension to balance the bike just a bit to match our speed and riding style – this is the first thing we do with all motocrossers. Once this was done the Kawasaki felt excellent – neutral and manageable in the air and steady and straight in deep bumps.

We really like the ergonomics of the KX450F, it takes no time at all to get accustomed to the narrow machine. The seat offers good grip and goes pretty much un-noticed while riding. Moving forward up over the tank for cornering is a breeze. We like the bend of the stock Renthal aluminum bars, but the bike really wears out your hands - the same as we found with the 2006 KX250F

The new suspension and aluminum frame soak up hard landings so well we often took to over-jumping and landing on the flat often - all without any worry. The Kawasaki’s ability to soak up insane landings can save your bacon time after time - or allow you to pass the rider next to you over a jump.

The new KX was proving fun to ride. The power is huge, straight line stability, bump absorption and shifting excellent. After spending more time on the track we couldn’t help but notice the 450F just wasn’t turning all that well. In sandy corners the bike pushes the front end, and in corners with excellent traction it just wasn’t living up to expectations or the turning prowess of similar machines. Not satisfied, we went looking for answers and finally settled on just adding a lot of pre-load to the rear shock to put more weight on the front end and cut down the steering angle slightly. The results were OK, but not completely satisfying.

We did get the 450 turning better which improved the overall fun and lap times, but we have to say this is the 450F’s one weak link. It turns, but it doesn’t turn like the competition. The new aluminum frame is surprisingly good – and it’s no cakewalk to come up with the proper flex and feel when designing a new aluminum frame. Even with the bikes massive power output, the frame and chassis make the bike easy to control and surprisingly forgiving. You can’t ride the 450F with wild abandon like the companies KX250F - particularly when hitting obstacle when partially leaned over. The KX450F likes to tackle nasty terrain when straight up rather than leaned over. With it’s greater reciprocating mass and greater momentum it can’t be tossed about as leisurely as a 250 4-stroke.

The brakes on the KX, with petal discs, are strong and predictable. As we found with the 250F, the front brake has more power than you think, you just have to keep squeezing the lever harder and harder. The brakes are nothing to complain about, but we’d like them better if the front binder required less lever pressure and provided a little more feedback.

Motorsports-Network Goes Off-Road Testing on the 2006 KX450F

As we all know, motocross machines like the KX450F are used off-road by legions of riders. With this in mind we set out to learn what the new KX is like in off-road use. Modifications are in order but we took the stock bike to the desert, and boy were we impressed. The 450F certainly displays good off-road manners.

A motocrosser normally has a more stiff suspension setup and provides less chassis flex than a bike designed for off-road use. With this said, the KX chassis provided good feedback and excellent steering manners across the desert as well as over tight trails. The suspension was a little stiff (we softened the fork compression setting by one click) but not harsh. Simply put, the faster we rode the bike off-road, the better it worked. The KX certainly has the right stuff for race speeds.

Over high speed whoops and slower nasty deep whoops, the KX displayed excellent and impressive control. With the machines monster power delivery it's easy to carry the front wheel over bumps - just lean back a bit and gas it. We discovered during our testing in an extremely deep and rocky (scary) whoop section that the rear shock is riding low in the stroke. This could have something to do with the machines less than stellar turning manners which were less noticeable in the desert. In nasty rock sections the bike surprisingly held its own.

One thing we didn't like was the low motocross positioned bars, which still wore our hands out. Taller bars are in order for off-road use. The seat felt good as well, but we didn't have a chance to take a long continuous ride. The controls felt excellent, but the Kawasaki doesn't offer quite enough adjustment to lower the rear brake lever as far down as we would like for larger boots. The brakes work well off-road, but we're still looking for more feedback to the rider - especially for off-road use.

Overall we were impressed with the stock KX450F off-road. The bike felt light, manageable and extremely powerful. The suspension, shifting and steering were excellent in the desert as well. The KX runs out of gearing quickly and it demands that you sit up over the tank to get the bike turned. Overall, this bike displayed excellent off-road manners. As a purpose-built motocross machine, you'll of course need to make some changes before seriously venturing off-road, beginning with a spark arrestor equipped more quiet exhaust.

Suggested Off-Road Modifications (by order of importance to us)

Quieter pipe and spark arrestor (it's loud)
Taller handlebars
Taller gearing
Larger skid plate
Hand guards
Larger fuel tank

Engine: Liquid-cooled, four-stroke single with DOHC and four valves
Displacement: 449cc
Bore x stroke: 96.0 x 62.1mm
Compression ratio: 12.0:1
Carburetion: Keihin FCR40
Ignition: Digital AC-CDI
Starting: Kick
Transmission: Four-speed with manual multi-disc wet clutch
Final drive: Chain
Frame: Aluminum perimeter
Rake / trail: 27 degrees / 4.6 in.
Front suspension / wheel travel: 48mm inverted AOS-type telescopic fork with 22-way compression damping and 20-way rebound damping / 12.4 in.
Rear suspension / wheel travel: UNI-TRAK® linkage system with 22-way compression and rebound damping, and fully adjustable spring preload / 12.4 in.
Front tire: 80/100-21 51M
Rear tire: 100/90-19 57M
Front brake: Single semi-floating 250mm petal disc with dual-piston caliper
Rear brake: Single 240mm petal disc with single-piston caliper
Overall length: 86.0 ins.
Overall width: 32.3 ins.
Overall height: 50.4 ins.
Wheelbase: 58.5 ins.
Ground clearance: 13.6 ins.
Seat height: 38.0 ins.
Dry weight: 220.1 lbs.
Fuel capacity: 1.9 gal.
Color: Kawasaki Lime Green / Black
MSRP (USA): $6,799


KX450F Test		2006 KX450F
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