TWO years after injecting its KX450F Kawasaki has finally done the same to its KX250F. Even though the previous KX250F was 'only' fitted with a carburettor it was still winning races and championships the world over. Now with fuel injection and totally new front forks, the 2011 model is set to do the same in the future.

Engine

Kawasaki’s 250cc four stroke engine is an absolute ripper. It is known around the world for its strong predictable power and excellent reliability.
For 2011 the green team has stayed with what it knows and has made some minimal but effective changes to its latest 250cc thumper. The bridged-box piston has been re-designed and now features a a new crown design. Along with a new shorter cylinder this will raise the compression ratio to 13.5:1 and make the bike feel more punchy and lively without compromising any reliability.

The intake cam timing has been modified along with a higher valve lift, all to better suit the new Digital Fuel Injection system. Once all this was complete the exhaust got an overhaul to meet the latest noise requirements.

The rest of the engine features on the KX250F are similar to years gone by, big strong radiators do a great job of cooling the little green thumper along with an excellent clutch and gearbox which will last forever and perform like the factory equipment. The final gearing has been shortened in 2011 to 13/50.

Electronic Fuel Injection

EFI is definitely one of the hottest topics being tossed around the pits at any MX track in Oz, so when Kawasaki made public that it was releasing fuel injection on the 2011 KX250F the stories and myths erupted of what was being expected by the weekend warriors around the country. For those who are stuck in the past and don’t do technology, this means the carburettor is gone, your collection of jets and needles are no longer needed and all the carby knowledge that you have built up over the past 100 years can go on the shelf, right next to all that two-stroke stuff. Digital Fuel Injection or ‘DFI’ if you like, is the technical name given to the new Fuel Injection System which has been specifically designed for Kawasaki’s latest Lites creation.

The Keihin system utilises a 43mm throttle body which is not too dissimilar to the body found on its older brother the KX450F. One of the key features of the Kawasaki DFI system lies within two linked shafts that control the throttle speed. Once the rider twists the throttle beyond the 3/8 mark the linked shafts work together to increase the opening speed of the throttle. This allows for sharper throttle response at higher RPM.

The injector featured is also a totally new design from the Kawasaki engineers, it is claimed to increase fuel flow by at least 20 per cent over its previous injector design which is featured on the current model KX450F. A nice touch which is available as an option on the KX250F is the KX FI calibration kit. It is an aftermarket plug in kit that enables the rider or mechanic to log onto the DFI system and make modifications to both fuel and ignition settings.

The pack comes pre-set with seven optimised fuel and ignition curves which were developed by the Kawasaki engineers. You can also play and fiddle as you like and create your own fuel and ignition settings using the software provided with the kit. Suspension In 2011 the Kawasaki engineers have introduced their revolutionary new Showa Separate Function front Fork system (SFF).

The new front suspension system is vastly different from any other 250cc four stroke on today’s market. In years gone by both damping and springs were housed together in the same fork. Not anymore, the left hand fork now houses the damping assembly only and the right hand fork takes control of the spring assembly.

This allows for dramatically reduced friction and a much smoother, more predictable ride. Kawasaki’s new fork design also saves significant weight over the previous system, the SFF set-up sheds the kilos by dropping parts which were previously needed twice. Now there is only one fork spring and damping system instead of two. It was also evident that after watching the Kawasaki technicians, the new Separate Function front Fork system is quite easy to adjust and simple to work on. All the normal clickers that we are used to seeing were still there, however there is now an added clicker adjuster on the top right hand fork to increase or decrease the amount of preload the rider/mechanic would like on the front fork spring.
The Uni-Track rear shock and linkage setup remains relatively unchanged from 2010.

The Showa shock gets revised damping settings to match the new fork setup and keep the green machine under control. The rest The moment you hop on the KX250F you feel comfortable and ready to go. Headlining the cockpit are Renthal 7/8” handlebars, we know they aren’t the oversize ’bars some riders expect but it’s pretty tough to bend a set of 7/8” Renthals. The bend is very comfortable and is actually the same handlebar that comes on one of its close competitors, the CRF250R.

The standard footpegs get the job done, however with the latest trend going towards platform wide-style footpegs it would be nice to see the KX with a big chunky set of ’pegs. Kawasaki has opted to fit out the new KX with Bridgestone tyres; the 403 front and 404 rear have an excellent reputation, they offer excellent grip in most conditions and don’t wear out too fast. The black wheels also make the KX look pretty trick. The overall look of the bike hasn’t changed from 2010 with the exception of the Bold New Graphics.

Considering the KX has a slick and modern new look, and that most 250F riders are going to kit their bikes out with new graphics and stickers anyway, having a similar look to last year can’t be a bad thing.

On the track

So what does all of the above mean on the track? It means the 2011 bike is considerably improved over the 2010 bike. When you first kick over the little green Kawie you notice the DFI has cleaned up the annoying splattering that you get under warm up on a carburettered four stroke.

DFI also loses the fuel on/off switch as the need is gone, however there is still a choke knob for those cold early morning race-day starts. Once the KX is all warmed up and you take to the track the feel at the throttle is much more predictable and gone is any evidence of a miss or flutter. We took it easy to begin with and got used to the set-up of the new fork and shock as well as the DFI.

The Showa SFF suspension does an excellent job of soaking up the bumps and feels nice and plush at the top of the stroke.
Once we began to tackle some of the bigger jumps the SFF forks and Uni-Track shock held up very well as we took on the big hits with confidence. The motor was very punchy and lively for a small bore thumper.
The little green machine pulls very strong off the bottom and doesn’t let off through the mid and top end. Once you spin a few laps on the KX250F it’s quite easy to see why this is a class leading engine.

Verdict

There is no doubt the 2011 KX250F is going to be a winner, especially at $10,999. Straight off the showroom floor this thing is in race-shape. With over 30 improvements to the 2011 model, Kawasaki has proved it isn’t resting and has taken its new machine to the next level.