Kawasaki KX250F - Special Edition eMag

Special EditionFull Test

Specifications

Now with:Fuel Injection

& SFF Forks

2011Kawasaki

w w w . c y c l e t o r q u e . c o m . a u

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Kawasaki has added some cutting-edge technology to make the KX250F even better for 2011…

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Test by Todd ReedPhotos By Nigel Paterson


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.

EngineKawasaki’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 InjectionEFI 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

Kawasaki’s KX250F has been one of the best motocross machines available in recent years – and for 2011 the

Green Machine has made it even better.

Perfectune


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.

SuspensionIn 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 restThe 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 trackSo 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.

VerdictThere is no doubt the 2011 KX250F is going to be a winner. 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. n


SFF Forks…Kawasaki claims its Separate Function front Fork (SFF) offers significantly

reduced friction, providing smooth fork action and firm damping performance. It’s the first time we’ve see a system like this on a

motocrosser: the Italians especially have produced suspension with the compression damping in one leg and the rebound in the other, but

Kawasaki’s gone a step further in dropping the spring from the left tube and putting all the damping responsibilities on just one side.

This cutaway shows the preload adjuster at the top of the left fork leg.

Changing spring rate means just switching one spring.


SFF Forks…

All the external adjustments are simpler and quicker, because there are less of them. There’s a preload adjuster on the top of the right fork leg (which simplifies

the task of setting fork preload or front ride height)Compression damping is handled by a single adjuster at the top of the left fork leg.

Rebound damping is controlled via a screw at the bottom of the left fork leg. Compression damping is handled by a single adjuster at the top of the

left fork leg.

Kawasaki claims another benefit of the SFF is reduced friction, resulting in better comfort and that means less fatigue.

Another benefit is an improved balance in the front end, as the weight of the disc and caliper offset the

weight of the spring in the right fork tube.


More power with Fuel Injection…IN TYPICAL Kawasaki fashion, the Green Machine isn’t the first to the party: the Kawasaki isn’t the first 250 four-stroke MX bike with fuel injection, but it could be the best.Aimed at experienced motocross racers, the 2009 model was basically all-new, the 2010 updated for more power and now the 2011 features improved bottom end and mid range, as well as better response, thanks to the adoption of fuel injection. But while having a good bottom-end and mid-range can be useful and handy (especially in the whoops, landing off jumps and in tight turns), winning motocross races is about top-end, and here the KX250F won’t disappoint, with the fuel injection improving the bike’s performance in the over-rev, too.The KX250F’s fuel injection system doesn’t require a battery, the kickstarter providing enough power to start the bike even when cold. It uses a small, designed-for-motocross lightweight ECU, located behind the front number plate and incorporating the fuel pump relay. One of the big advantages of fuel injection is it removes the need to adjust for altitude and climactic conditions, the electronics doing that on the fly.Because the 250 revs much harder than the 450, the KX250F’s injector holes are actually 20 per cent larger than the bigger bike’s. It also features a progressive throttle link – two linked shafts means the throttle opens quicker after 3/8 throttle to deliver better response and feel. The 43mm throttle body is about half the weight of a carburettor. There’s an aluminium fuel pump in the 7.2-litre fuel tank which has a fuel trap to ensure it always has fuel to deliver to the EFI despite the rigour of motocross.

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5 67

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ECU mounting bracket(replacement part for use with kit)

Controller bracketECU controller

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Wire harness clampController bandsUpper/lower controller dampersController damper

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Controller sub-harnessUSB cableSoftware CD-ROMPower supply harness

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2 0 1 1 M Y K X 2 5 0 F M O D E L I N F O R M A T I O N 8

KEY FEATURES

* While the kit is designed to satisfy racers and expert riders, it is simple and hassle-free to use:

- the ECU controller mounts behind the number plate for easy access - accessing the ECU is accomplished simply by connecting to a PC via the ECU controller using a USB cable (no additional switches are necessary) - setting adjustments can be prepared in advance on a PC, or done when connected to the ECU - the kit’s user-interface is simple to understand and easy to use

* The KX FI Calibration Kit contains seven preset settings that can be quickly and easily used to adjust the ECU to suit track conditions. The provided settings are shown below.

* The KX FI Calibration Kit contains KX Racing software, an ECU controller, mounting brackets and damper, harness and USB cable. In addition to the kit, a PC and 12 V battery are all that is required. (Photo 7)

NEW

The KX FI Calibration Kit is the same kit used by Kawasaki’s works teams in Europe and the U.S. The kit enables expert riders to adjust engine characteristics (by rewriting actual data maps) to suit their preference, record riding data, and analyse their riding data to further fine-tune their settings.

Factory KX FI Calibration Kit (option)

NEW

NEW

SETTING

Richer fuel setting

Leaner fuel setting

Advanced ignition setting

Retarded ignition setting

Hard riding surface setting

Soft riding surface setting

Beginner setting

DESCRIPTION

fuelling 5% richer than stock

fuelling 5% leaner than stock

ignition advanced 3o from stock

ignition retarded 3o from stock

ignition retarded, fuelling richer

ignition retarded, fuelling richer

engine power suppressed: ignition retarded, fuelling richer

most sample maps offered in industry

7PRESETS

only data logging function in industry

6DATA

LOGGING

-HOUR

choice of display

or

DISPLAY

The ECU incorporates the fuel pump relay and is safely nestled behind the front number plate.

The throttle body is lighter than a carburettor and features twin shafts (see below) for better feel and progressive fuel delivery: fuel delivery gets more

aggressive as you do.

The fuel pump is designed to ensure a consistent supply of

go-juice to the EFI even as you’re smashing berms and

jumping triples.

The injectors actually supplies more fuel than the unit off the 450, because the 250 revs harder.

The optional KX FI calibration Kit is the same as what’s used by Kawasaki’s top teams around the world. Stock there are seven presets which can be set quickly and easily, but there’s more you can do if you need to. It also works as a datalogger, recording up to six hours of engine data.


…and engine updates

The barrel is slightly updated from 2010.

Revised muffler baffling for reduced noise.The bridge-box bottom piston has been updated for 2011. The unique mass produced design is both strong and light.

For the 2010 KX250F, Kawasaki concentrated on performance, and made the bike one of the fastest in the field. While the biggest changes for 2011 focus on the fuel injection, Kawasaki hasn’t ignored the engine. Retained but updated is the bridged-box bottom short-skirt piston. This design features fully-flush internal bracing to make the piston stronger and lighter. The piston crown has been updated to suit the better over-rev and top-end, compression is up by 0.3 to 13.5:1 and the cylinder height reduced accordingly.Other changes include different valve timing, increased valve lift and stronger valve springs.Increased intake ducting and a new spark plug extending further into the combustion offset the usual loss of performance at the bottom-end associated with a switch to EFI.A 48-tooth rear sprocket replaces the 50-tooth unit on the 2010 model, and the exhaust pipe is 30mm longer to suit the new engine characteristics, but noise is actually reduced thanks to new internal baffling.


SPECIFICATIONS KX250YBFENGINEType: Liquid-cooled, 4-stroke SingleDisplacement: 249ccBore and Stroke: 77.0 x 53.6mmCompression ratio: 13.5:1Valve system: DOHC, 4 valvesFuel system: Fuel injection: ø43 mm x 1 (Keihin)Ignition: Digital DC-CDIStarting: Primary kickLubrication: Forced lubrication, semi-dry sumpTransmission: 5-speedFinal drive: Chain, 50/13-tooth sprockets

FRAMEType: Perimeter, aluminiumWheel travel: front 315mm, rear 310mmCaster (rake): 28.2 degrees

SUSPENSIONFront: 47 mm upside-down telescopic Separate Function front Fork (SFF). Fully adjustable for spring preload, compression damping and rebound damping.Rear: New Uni-Trak (linkage type with spring/damper unit). Fully adjustable for spring preload, high and low speed compression damping and rebound damping.

BRAKESFront: Single semi-floating 250 mm petal disc with dual-piston caliperRear: Single 240 mm petal disc with single-piston caliper

DIMENSIONSOverall length: 2,170mmOverall width: 820mmOverall height: 1,270mmWheelbase: 1,475mmGround clearance: 330mmSeat height: 945mmCurb mass: 105.7kg (EUR/AUS/JPN/BRA)Fuel capacity: 7.2 litres

Price: RRP $10,999

More info

www.kawasaki.com.au

Radical new SFF forkThe KX250F is the fi rst mass-production Motocrosser to feature the radical new Separate Function front Fork (SFF) with 25% less friction than standard forks.

Radical new SFF fork NEW Digital fuel injectionThe KX250F’s new fuel-injection system delivers immediate throttle response, pin-point tuning and automatically adjusts to suit track and climate conditions.

Making History: 1-2-3-4In 2010 the KX250F won the AMA East and West Supercross Lites titles and fi nishing 1-2-3-4 in the East Vs West SX Lites Final showdown.

NEW

NEW smooth action, low-friction Separate Function Forks NEW digital fuel injection delivers immediate throttle response NEW programmable ECU (via optional calibration kit) Factory-spec engine tuning boosts high-rev performance Updated shock absorber with dual compression adjustability Lighter handling chassis with increased rear wheel traction

Go to www.kawasaki.com.au for the latest Kawasaki motorcycles, news and dealer information Photograph depicts a professional rider under controlled conditions. Kawasaki Motors Pty Ltd endorses safe riding. Always wear an approved helmet and protective riding clothing. Never ride a motorcycle under the infl uence of alcohol or drugs.

Kawasaki KX250F - Special Edition eMag

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