2011 Kawasaki KX250F

It's an old refrain: The factory guys get all the good stuff. Their bikes are faster, lighter and just plain tricker than the motocrossers you can buy off the showroom floor. There's some truth there. But that's changing. The gap between production and factory-prepped motocrossers has never been narrower. And with the introduction of Kawasaki's massively reworked 2011 KX™250F, that gap just shrank a little more.

All told, there are nearly 30 upgrades to the new KX250F, all of which reflect the stunning level of testing and development happening behind the scenes at Kawasaki's R&D and race teams. And Kawasaki does this for one reason: To put you on the fiercest, most capable motocrosser in the industry.

When reworking the new KX250F, engineers started with what's arguably already the gold standard in 250-class racing - the 2010 KX250F. Just ask Christophe Pourcel and Jake Weimer, who won the 2010 AMA East and West Lites titles, respectively, on their Monster Energy™/ Pro Circuit / Kawasaki-backed KXs. Or read the long list of enthusiast magazine shootouts that picked the 2010 KX250F as the best motocrosser in its class.

For 2011, the goal was an even faster and more ridable KX250F. On the more powerful side of the equation are loads of engine modifications, all of which have made the latest KX an absolute corner-to-corner screamer. The big news is the addition of Digital Fuel Injection (DFI®) that not only helps produce stunning - and more useable - power, but also makes tuning a much easier proposition. The system, basically identical to the one fitted to the 2011 KX450F, automatically adjusts to suit track and climate conditions, and offers consistent fuel metering and response even when the going gets rough, such as when landing off jumps or slamming through the whoops. The simple and highly efficient DFI system incorporates a compact and lightweight Electronic Control Unit (ECU), a 43mm throttle body, a lightweight aluminum fuel pump and an ultra-fine atomizing injector. Set at a 45-degree angle for optimum mid-range power, the injector shoots precisely metered fuel directly into the intake tract for smooth power delivery and highly accurate engine response throughout the entire rpm range. The 250F's injector actually flows more fuel than the 450F's unit due to the 250F engine's higher speeds, while airflow through the system is actually higher than through the 2010 model's carburetor setup.

Designed specifically for motocross, the KX250F's lightweight DFI system requires no battery; the engine can be started within three rotations of the crankshaft using only the electricity generated through the initial stroke of the kickstarter. What's more, an optional ECU Setting Tool allows racers to select from several different ECU data maps, or fine tune a custom map that alters fuel injection and ignition timing to suit different tracks and conditions. The tool can also be used as a data logger, recording up to six hours of data, including engine rpm, degree of throttle opening, coolant and air temperatures, ignition timing, fuel adjustments, gear position and system voltage.

You'll find more significant changes farther downstream, such as higher compression - now 13.5:1 vs. 13.2:1 - via a modified cylinder and changes to the top of the exclusive Bridged-Box Bottom piston. The intake camshaft now produces higher valve lift, while the intake valve spring is stronger to handle the extra load. The crankshaft's rotational inertia has been slightly modified to better match the new engine's characteristics, while a slightly longer spark plug design - and a new coil offering a hotter and longer-duration spark - improves combustion performance. Transmission and final-drive ratios have been altered slightly to match the engine's newfound response, and a modified shifting mechanism allows you to access those speeds more easily and smoothly. There's 10% more air-cleaner duct volume for better breathing, and on the exhaust side, a longer head pipe gives the engine a touch more low-end power, while a higher-volume muffler assembly lowers noise to comply with the 94 db AMA Pro Racing limit, while retaining optimum power production up top.