The new Kawasaki motocross bikes are here. As expected, the KX450F gets minor refinements as the R&D team recovers from the massive overhaul in 2009, but the KX250F isn’t the big news we were hoping for. It still received a list of changes, but, I’ll go ahead and spoil it right here, it still has a carburetor. Thanks to slower sales and an abundant inventory supply of KX65 and KX100 models, both 2-stroke machines are on a production hold for 2010. Kids who want fresh greenery will have to look for the KX85 which gets aesthetic upgrades. Read on for the specifics of each Kawasaki dirt bike model.
The 2010 Kawasaki KX450F is an updated version of the bike that won our 2009 450 Motocross Comparison.
2010 Kawasaki KX450F
Last year’s version blew the doors off with all-new fuel injection, but for 2010 the KX450F isn’t changed as radically. This burly beast is only refined for the new year with adjustments you can’t see from the outside. Inside the motor is a new bridged-box piston. It shaves seven grams and has a 6mm-shorter skirt. Kawi claims it increases performance at the top of the rev range. The intake cam timing is advanced two degrees and ECU settings are tweaked. Kawi says the piston design has been proven through use in the race team bikes along with a wedge-shaped crank which is already in use. By offsetting 60% of the crankshaft’s reciprocating weight, it acts as a counterbalance to smooth the engine delivery and vibrations.
The bike gets 40mm trimmed off the single-piece head/mid-pipe and the friction plates in the clutch get 75% more material. Denso radiators are 10mm taller and 7.6mm wider which brought about new shrouds. The bodywork mounts to a chassis that features a new steering stem shaft with the goal of decreasing rigidity. The Kayaba fork gets a different spring rate and revised damping to ease the initial stroke. The same goes for the rear end where the shock mounts to revised linkage ratios.
A revised ECU tunes the motor and FI.
2010 Kawasaki KX450F Specs:
Engine: Liquid-cooled, 4-stroke Single with DOHC and four valve cylinder head
Displacement: 449cc
Bore x stroke: 96.0 x 62.1mm
Compression ratio: 12.5:1
Fuel Injection: 43mm Keihin Throttle body
Ignition: Digital DC-CDI
Transmission: Five-speed
Rake / trail: 26.7 degrees / 4.6 in.
Front suspension / wheel travel: 48mm inverted, Kayaba AOS with DLC coated sliders, 22-position compression and 20-position rebound dampening adjustment / 12.4 in.
This is the disappointing news for 2010, but the KX250F is still going to be one fast motocross bike. We'll just have to see if any of the other OEMs put fuel-injection on their 250F machines.
2010 Kawasaki KX250F
We were hoping the trickle-down effect would happen fast enough for this year’s bike to trade its carburetor for digital fuel injection, but it wasn’t to be. Try not to be too disappointed, though. We had to remind ourselves that the ’09 was a damn fine machine, and a list of improvements aimed at bettering the handling characteristics is a good thing.
Kawi’s quarter-liter gets a bridged-box piston design like the KX450F as well as the wedge-shaped crank web and larger radiators. But, unlike its big brother, the exhaust pipe is longer out of the head and shorter in the middle for boosted low-end grunt. Crankcases are thicker and the tranny is beefed up as well with bigger dogs on third and fourth gears.
Suspension and chassis changes are just like the 450 except that the KX250F uses Showa components. The steering stem has less rigidity and the suspension tuning aims at leveling the bike’s stance so that there is less pressure on the front wheel. That doesn’t necessarily equate to quicker handling in the hypothetical world, but we’ll wait and see how this thing turns at the press launch.
Sure seems like there’s a lot in common with the 450F, and the price hike is no different. If this is the bike for you, the 2010 model rings in at $6999 - an extra 500 bucks over the ’09. Keep your fingers crossed for some First Rides on the KX450F and KX250F in August and September.
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