New Bike Season: Kawasaki KX250F 3

Monster Energy Kawasaki's Ricky Dietrich, putting the new Kawasaki KX250F through its paces.

Ah yes, we’re here to look at a seriously updated Kawasaki KX250F, which has been the weapon of choice for the Monster Energy Pro Circuit Kawasaki squad…and you know how successful they’ve been with it since its introduction. Mitch and the crew have been running out of space on the doors of their rig, and recently had to redo all the number one plates in a smaller scale to make them all fit.

Getting antsy for a new bike? Ready to look over all the changes? Let’s go…

Engine Changes

Of course, the biggest news is that the KX250F joins the ranks of Suzuki, Honda, and the other 2011 addition to the ranks, KTM, in the fuel-injected club. Kawasaki has dubbed theirs DFI (Digital Fuel Injection), rather than EFI. As per usual, the fuel injection system monitors air pressure and temperature, as well as the internal water temperature, gear selection, and whether the bike is down or not.

The addition of the fuel injection is good news for the '11 KX250F, and it uses the same throttle body as its bigger brother, the KX450F.

The basic system is the same as the one used on the KX450F, with a 43mm Keihin throttle body, which offers more air flow than last year’s carb, and is actually the same size as the one used on the KX450F. It also uses the same progressive throttle link, which speeds opening of the throttle from 3/8 to WFO.

Interestingly, the 250F actually uses a fuel injector that offers 20 percent more capacity than the one used on the KX450F. It may sound odd, but the 250F actually requires a faster fuel output race because of the higher engine RPMs. It also uses the same fuel pump as last year’s KX450F.

The benefit is similar to other fuel injection systems. There’s a boost in throttle response and the elimination of bog (especially after landing from jumps), and a more linear power delivery. Ah yes, it also allows for easier tuning via a laptop…though the optional tuning kit that can be used for both tuning and data logging is specific to the 2011 model (and can also be used on the KX450F).

How about other internal changes to the powerplant? Here goes.

The piston crown shape has changed for more overrev, and a boost in performance at high RPM.

A slight overall reduction in cylinder height bumped the compression from 13.2:1 to 13.5:1.

For better engine response at low RPMs, they boosted the size of the air intake, and on the exhaust side the length of the headpipe was increased 30mm. We were also stoked to see a larger muffler, and a claimed drop from 99db to 94db.

Ignition changes? Yep. There’s a larger stator and rotor to power the DFI setup, and the coil has changed from a stick type to a coil with a high tension lead for better fuel burn.

The diameter of the crank at the taper mount gets boosted from 18 to 21mm, and they’ve adjusted the rotational intertia, as well as changing the crank’s wedge shape, while maintaining the same balance ratio.

In the transmission, second and fourth gears both get adjustments (1.769 to 1.750 for second, and 1.200 to 1.235 for fourth) to better match the power characteristics of the fuel-injected engine. The same goes for the rear sprocket, which was bumped up by two teeth. The shifting mechanism also gets a tune-up with a longer shift stroke, along with a reduced spring tension, and a change in the angle of the ratchet to boost gear engagement.

Suspension and Chassis Changes

While the change to fuel injection was cool (and maybe overdue), the item that seemed to attract more attention was the new Showa Separate Function Fork (SFF), which is an exclusive for the Kawasaki.

Here's a cutaway look at the Showa Separate Function Fork. As you can see, in the left side of the shot (which is actually the right leg), one side houses the spring and preload, while the other houses the new larger damper.

What’s different about it? Quite a bit, actually. Rather than having a system that’s mirrored, with dampers and springs on the left and right sides, the SFF uses one much larger fork spring in the right leg, and uses the left leg to house a damper that also has a larger volume than before. That means you get a reduction in friction (only one oil seal) by a claimed 25 percent. You also get simpler tuning, with one compression adjuster on top of the fork leg, and one rebound adjuster on the bottom.

The top of the caps show the simplified tuning package. Just one compression and rebound to fiddle with, and the addition of a new external preload adjuster.

But having the single damper also has also opened up the fork to some additional tuning capabilities. Showa built in a preload adjuster, so you can now change the preload without having to open up the fork, and adjust the ride height of the front end. If you prefer having the front end choppered out a bit (like Ricky Dietrich, who guest rode for us during the media day), that’s easier to achieve than in the past.

One thing that hasn’t changed on the new design was the use of a Kashima coating on the interior of the fork legs, and a titanium coating on the lower legs.

The rear shock also benefits from the same Kashima coating used on the forks, which is another Kawasaki exclusive, and they’ve also tuned the shock to match the character of the fork.

In an effort to increase front wheel traction and improve handling, the fork offset was reduced 1mm, from 23.5 to 22.5mm.

Kawasaki also suggested that tuning costs at a suspension hop-up shop could potentially be reduced, since there’s only one spring to replace, or damper to tune. While that remains to be seen, we did check in with Jim “Bones” Bacon at Pro Circuit, who told us that he’s looking forward to getting his hands on the forks, and that Showa had already addressed all of the concerns that he’d expressed about the new design.

Were you looking for some additional lateral flex in the frame over the 2010 model? Kawasaki was, and changed the engine brackets from aluminum to steel, and thinned them considerably both on the front and rear.

Other changes in the chassis include a much thicker chain guide on the swingarm, and a boost in the grippiness of the seat cover.

Add it all up, and you get a chassis that Kawasaki claims is their best ever, with a lighter feel, and improved cornering precision that requires less steering input, as well as improved front wheel traction.

With the DFI, and new fork, the KX250F is substantially upgraded from the 2010 package.

Suggested retail for the package? $7,299, and we’ve heard reports that they’re already in dealers now.

Check the video below for more with Russ Brenan from Kawasaki, Mitch Payton from Monster Energy Pro Circuit Kawasaki, and Monster Energy Kawasaki’s Ricky Dietrich.

New Bike Season: 2011 Kawasaki KX250F