At least here in the United States, Kawasaki can make a pretty good case that its KX250F is the most effective race weapon in the 250 class at the pro level. Among other recent championships, Kawasaki captured both the East Coast and West Coast Lites Supercross championships this year (with Jake Weimer and Christophe Pourcel) using a 2010 KX250F tuned by Pro Circuit. We were very impressed by the 2010 production machine.
For 2011, Kawasaki introduces a new model that indicates it has been busy improving an already excellent package by making close to 30 changes. Most notably, the KX250F now features fuel injection and a unique 47mm Showa fork that separates spring and damping functions between the right and left fork legs. According to Kawasaki, the new fork is lighter, adjusts more simply and effectively (including a spring preload adjustment on the right fork cap) and offers a significant 25% reduction in stiction.
The fuel injection system is similar to the one found on last year’s KX450F, and does not require a battery. It actually flows more fuel on the 250 due to higher engine speeds. Overall, the 250 gets a denser fuel/air mix this year, including a new air-cleaner duct that increases air flow by 10%.
The engine gets compression boosted to a stratospheric 13.5:1 (last year it was an already high 13.2:1). Intake valve timing has been changed, and even the spark plug design has been revised in a manner that, together with a new coil, offers a hotter and longer-duration spark.
Both the new fork and the rear shock are fully adjustable for rebound, compression and spring preload. Along with the new fork, the rear shock gets revised damping settings for 2011.
There are plenty of additional detail changes, including a new seat with grippier cover.
Like the 450, an optional FI tuning kit can be purchased from Kawasaki that comes with 7 pre-set maps, as well as the ability to create custom maps that change both ignition timing and fuel flow rate.
Kawasaki tried to improve shifting this year by slightly increasing the rotational angle of the shift lever, and correspondingly adjusting return spring tension.
The exhaust pipe now has a longer header section, and incorporates a muffler that reduces sound levels significantly to comply with new racing noise limits.
Kawasaki modified both internal gearing and final drive gearing for 2011 to better match the performance characteristics of the revised engine. The swingarm is also slightly longer this year.
We had a chance to test the 2011 KX250F over two days at the Budds Creek Motocross Park recently. We have seen some manufacturers, on occasion, take a step backwards with new motocross bikes. Given the quality of the 2010 KX250F, and the sometimes difficult proposition of incorporating fuel injection for the first time, we had some concerns.
The new fuel injection system works extremely well. Although the 2010′s carburetor jetting was pretty much spot on, the new FI system only makes throttle response crisper and more immediate, without being jumpy.
The 2011 KX250F feels like it has slightly more power than last year’s excellent engine, and delivers it in a smoother, more forgiving manner across a broader rpm range. Bottom end feels stronger, but the bike still revs out very hard. In addition to the new fork, Kawasaki slightly changed steering geometry by reducing fork offset from 23.5mm to 22.5mm. Initially, the 2011 model exhibited some reluctance to lay over in the turns and stay in ruts, but after a quick adjustment to the fork preload to balance our test rider’s weight (over 200 lbs), the handling improved dramatically. So much so, in fact, we really can’t criticize it. The convenient, external fork preload adjustment located on the top of the right fork is a godsend. This is the only fork currently offered by a Japanese manufacturer on a motocross bike with this feature (remember the days when you had to go to the hassle of removing the fork cap and cutting a section of PVC pipe to adjust spring preload?).
The bike shifted well, and the revised suspension allowed it to hook up well exiting corners and remain balanced throughout the track. In addition to the excellent cornering ability, the bike tracked straight and was very stable at high speeds.
Negatives? The only one that comes to mind is the bike seems a bit harder to start this year (averaging three kicks). Other than that, we have to say that Kawasaki was successful in improving the excellent 2010 model. The 2011 KX250F could be raced by riders at virtually all skill levels, from novices to experts. For additional details and specifications, check out Kawasaki’s web site. The U.S. MSRP of the 2011 KX250F is $7,299.