2011 KAWASAKI KX250F MOTOCROSS TEST: KAWASAKI DROPPED THE CARBURETOR AND ONE FORK LEG FOR 2011

December 9, 2011
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Q: FIRST AND FOREMOST, IS THE 2011 KX250F BETTER THAN THE 2010 KX250F?

A: 
The unvarnished truth is that the 2011 lacks some of the raw feel that made the 2011 such a great motocross machine.

Q: WHAT ARE THE BIGGEST CHANGES ON THE 2011 KAWASAKI KX250F, AND ARE THEY WORTH ALL THE FUSS?

A: The Kawasaki marketing department was quick to point out that the 2011 KX250F underwent nearly 30 changes. Rather than bore you with all of the details, we’ve boiled down the list to three primary areas of importance.

(1) Digital Fuel Injection. The big rumor leading up to the release of last year’s 2010 KX250F was fuel injection. It didn’t happen. Kawasaki wasn’t happy with how the EFI system changed the performance of the engine, so they held off a year. The 2011 KX250F comes with fuel injection.

Don’t be confused by the Digital Fuel Injection (DFI) terminology. DFI is Kawasaki’s homegrown marketing jargon for electronic fuel injection. The 2011 KX250F shares the same fuel injection system as the KX450F, including the 43mm Keihin throttle body. A note of interest is that while the 2011 KX250F uses the same fuel pump as the 2010 KX450F, the 2011 KX450F has a different pump. The ECU settings are also different between the KX250F and its big brother.

(2) SFF system. It wasn’t a big shocker that the 2011 KX250F came with fuel injection, but what did surprise us was Showa’s Separate Function Fork (SFF) system. Borrowing technology from the mountain bike industry (with a little nod to 20-year-old Marzocchi M1 motocross forks), Showa’s SFF uses one heavy fork spring as opposed to two lighter springs.

How is the system designed? The right fork leg contains a 0.93 kg/mm spring that is over twice as firm as last year’s fork springs (which were 0.44 kg/mm). There is also a minimal amount of oil in the right leg for lubrication of the compression rod, air  chamber and a preload adjuster. The left fork leg contains the piston rod damper, air chamber and most of the fork oil.

The Separate Function Fork is an interesting concept because it is easier to work on (no doubt aftermarket suspension companies are feverishly working on making SFF-specific parts as you read this test). Additionally, the spring on the single-spring fork can be adjusted via a dial atop the right fork leg. Six clicks of the dial equal 1mm of preload (Kawasaki recommends setting the fork ride height between 45mm and 55mm).

(3) Handling. The KX250F has always suffered from a front-end push from center-out in corners and a shock that wallowed dreadfully under acceleration. Last year, Kawasaki hedged their bets by decreasing the size of the steering stem shaft and lengthening the pull rods and rocker arm. The refinements helped the handling traits, but not nearly as much as the MXA test crew had hoped for. Kawasaki responded in 2011 by reducing the fork offset from 23.5mm to 22.5mm.

Kawasaki has often toyed with the material and thickness of their engine brackets. For 2011, the KX250F will have thinner (4.5mm) steel front and rear brackets as opposed to thick (6mm front and 8mm rear) aluminum brackets. These incremental changes are a result of finding the proper rigidity balance for the chassis.

Q: WHAT OTHER NOTABLE CHANGES DID KAWASAKI MAKE TO THE 2011 KX250F?

A: In the engine department, they modified the valve timing, changed the cam profile (by increasing valve lift), strengthened the intake valve spring tension, raised the piston crown shape, raised the compression ratio (13.2:1 to 13.5:1), reduced the cylinder height, increased the crankshaft diameter at the taper mount and changed the crank web shape. In the transmission, second gear is shorter and fourth gear is longer. Kawasaki revised their gear shifting mechanism for the umpteenth time by modifying the ratchet and lever while reducing the return spring tension. Other KX250F changes include a higher volume air filter duct, longer head pipe, lower gearing (13/50 instead of last year’s 13/48 combination), longer swingarm, thicker chain guide, and grippy material on the sides of the seat cover.


Suspense: We were surprised at how well the Kayaba SFF forks worked (once we got the right spring in them). We were disappointed in the brakes, shifting and clutch.

Q: WHAT DIRECTION DID KAWASAKI TAKE WITH THE 2011 KX250F?

A: Before we answer this question, it’s necessary to discuss the history of the KX250F. Although Kawasaki hasn’t built the fastest, lightest or best-handling bike, the KX250F has earned top honors in MXA‘s 250 Four-Stroke Shootout four of the last five years. How is this possible? Kawasaki capitalized where other manufacturers faltered. The KX250F hasn’t belched fire-breathing power, but the powerband has typically been well-balanced and strong enough for the vast majority of riders. The suspension has been suspect, but not glaringly bad. The weakest area of the KX250F has been the handling. With that said, we always found simple solutions to the front end’s refusal to turn sharply and the rear end’s tendency to wallow. Suffice it to say that the KX250F hasn’t been a world beater, but is instead a bike with excellent potential.

Kawasaki seems to listen to the MXA wrecking crew’s complaints, but it would be narcissistic for us to think that Kawasaki designs their bikes specifically for us. While that would be nice, it’s just not the case. Kawasaki must take consumer opinion, technological advancements and the inherent costs associated with them, sales objectives and the bottom line into account when developing a new model. That’s what they did for 2011.

The 2011 KX250F will forever be defined by the Showa Separate Function Fork more so than the fuel injection system. For 2011, every 250 four-stroke aside from the Yamaha YZ250F is equipped with fuel injection, but no other manufacturer has a radically different suspension system. The only question that remains is whether the SFF system is all that it’s cracked up to be.

Q: HOW DOES THE 2011 KX250F COMPARE TO LAST YEAR’S MODEL ON THE DYNO?

A: Maximum horsepower on our 2011 KX250F was 37.30 ponies at 12,600 rpm. Maximum torque was 18.90 foot-pounds. For comparison, our 2010 KX250F reached 36.48 horsepower at 12,000 rpm and produced 19.53 foot-pounds of torque.

While the 2011 model is almost a horsepower stronger at peak performance and high rpm, the 2010 KX250F romps it everywhere else on the dyno curve. From 6000 to 8200 rpm, the 2010 model produces roughly two more horsepower than the 2011 and is nearly a pony better from 8700 rpm through 11,000 rpm. It isn’t until 11,700 rpm that the 2011 KX250F trumps the old engine. This doesn’t bode well for the 2011 KX250F.

Comparing apples to oranges, the KX250F is consistently down at least a horsepower to the 2011 KTM 250SXF until 9000 rpm, yet the Kawasaki holds a horsepower advantage at peak. On the torque scale, the 250SXF pumps out one full foot-pound more than the KX250F.

To summarize, the 2011 KX250F has a short powerband with fair torque but plenty of horsepower. It’s too bad that up until 11,700 rpm the KX250F gives up so much ground to its competition. The reason for the short powerband? All signs point to fuel injection. It became clear on last year’s Honda CRF250 that electronic fuel injection hindered the engine’s performance. The only bike to defy such logic thus far is the 2011 KTM 250SXF, which actually produces more horsepower than the 2010 250SXF over the majority of the dyno curve.

Q: HOW GOOD IS THE POWERBAND ON THE 2011 KAWASAKI KX250F?
 
A: With our incessant comparisons between the 2011 KX250F and other bikes, as well as the lackluster dyno run, you might think that we hate the KX250F’s powerband. Your assumption would be wrong. Although the engine isn’t as powerful or fun as the 2010 KX250F, it will still hold its own around the track. The 2011 powerplant feels electric, thanks to the electronic fuel injection. This isn’t necessarily a bad thing, but test riders were left searching for the snap that the KX250F had become known for. We never found it. Instead, we discovered that the engine does its best work from the midrange into the top end. Although the bike has a short powerband, it is most potent just a hair below the rev limiter. We believe that the 2011 KX250F should be ridden in the penthouse of the powerband?that is, at full tilt.

The KX250F powerplant works best in the hands of a rider with vigor, who winds the engine to the moon. Only then will the high-revving engine mask the soft spot from the bottom end into the midrange. Lugging the KX250F is a bad idea. Keep the throttle cable stretched, use the clutch frequently, and ride with aggression.

 
 
Word: Electric is the best adjective for the KX250F engine. Fork offset: Kawasaki is inching closer to what local racers run.

Q: DOES THE 2011 KAWASAKI KX250F PASS THE AMA SOUND TEST?

A: Yes, but you’re out of luck if you’re racing in Europe. The KX250F passed the AMA’s loose sound regulations at 91.9 dB. This is a 1.6 dB decrease from the 2010 KX250F. The AMA sound test requires that all 250 four-strokes must be at or below 94 dB at 5000 rpm for AMA competition (although in reality they allow up to 95.9 dB). With that said, the KX250F failed the FIM’s two-meter-max sound test, which takes a decibel reading two meters away from the muffler with the throttle wide open for a split second. The FIM’s sound test makes more sense, since 250 four-strokes are ridden wide open and not at a purring 5000 rpm. The KX250F hit 119 dB, while the legal limit is 115 dB.

Test riders mentioned that the 2011 KX250F was quieter than last year’s model, although it still had a rather loud and raspy sound at speed. Also, we noticed a whirring sound from the EFI system, but only by attentive ears.

Q: WHAT IS THE SUGGESTED RETAIL PRICE OF THE KX250F?

A: The KX250F retails for $7299. The 2010 Kawasaki KX250F retailed for $6999. For the sake of comparison, the 2011 KTM 250SXF retails for $7699 and the 2011 Honda CRF250 goes for $7199 (the other manufacturers hadn’t released pricing information at the time of this test).  

Q: CAN YOU REPROGRAM THE IGNITION?

A: Yes. Kawasaki sells the software that makes reprogramming the ignition possible. Although the software isn’t as intuitive as the Yamaha GYTR Tuner (it requires a PC-based laptop and a battery to charge the ignition), it does work quite well. The $617 kit comes with the software CD, the plug that goes into the wiring harness, the harness itself, and the lead that connects to a battery (the 12-volt battery doesn’t come with the kit). Testers tried several different Kawasaki-tuned maps and found benefits in the changed ignition at various tracks. The software comes with seven different preset ignition maps from Kawasaki.

Do not expect the mapping software to radically improve the horsepower of the 2011 KX250F. As we have discovered on all fuel-injected bikes, adjusting map settings only affects the character of the engine; it does not pump out more ponies. Technology buffs will geek out on the possibilities that the software does offer, but don’t expect a completely different powerband.

Q: HOW WELL DOES THE SHOWA SFF SYSTEM WORK?

A: Showa’s Separate Function Fork system works extremely well..or rather has the potential to work extremely well. Test riders were pleasantly surprised with the fork’s ability to perform in a plethora of situations (given it’s overly soft setup). The SFF system had smooth fluid action through the entire stroke. Any rider over 170 pounds or faster than Novice will find it necessary to swap out the stock 0.93 kg/mm fork spring for a heavier 0.97 kg/mm or stiffer spring. A heavier spring allows the forks to stay up in their stroke and offer full travel in high-stress situations.
    
Q: WHAT ARE OUR BEST FORK SETTINGS?

A: Here is what the MXA wrecking crew ran in its 2011 Kawasaki KX250F (stock settings are in parentheses):
    Spring rate: 0.97 kg/mm (0.93 kg/mm)
    Oil height: 155cc (right leg), 357cc (left leg)
    Ride height: 51mm
    Spring preload: 22 clicks out
    Compression: 8 clicks out (7 clicks out)
    Rebound: 8 clicks out (10 clicks out)
    Fork leg height: 7mm up
    Notes: The KX250F’s handling traits are dependent on ride height. Too much ride height yields a vague feeling at turn-in. To measure the ride height, have the rider sit on the bike. Measure from the bottom of the right fork guard to the dust seal. Also, if you have to go less than six clicks out on compression, then you should step up to the next stiffest spring rate.

Q: WHAT IS OUR BEST SHOCK SETTING?

A: Here is what the MXA wrecking crew ran in its 2011 Kawasaki KX250F (stock settings are in parentheses):
    Spring rate: 5.2 kg/mm
    Race sag: 100mm
    High-compression: 2 turns out
    Low-compression: 9 clicks out (11 clicks out)
    Rebound: 11 clicks out (10 clicks out)
    Notes: We think that the KX250F works best with the low-speed compression turned in while using the high-speed to adjust the ride height at speed.


2011 Kawasaki?KX250F: Kawasaki could have sat pat and waited to see if anyone could come close to their class-leading 2010 KX250F. Instead, they reinvented the wheel?even if it still looks the same.

Q: HOW DOES THE 2011 KAWASAKI KX250F HANDLE?

A: The 2011 model is the best-handling KX250F that we have ever ridden. But before you get all misty-eyed, you should know that the KX250F has never handled all that well. The front end pushed entering corners and felt vague, and the rear end wallowed under heavy acceleration. For the past few years MXA has found solutions to Kawasaki’s handling woes. We swapped out the stock triple clamps for 22mm offset clamps, used a longer pullrod and tinkered with the fork leg height.

Last year, Kawasaki attempted to solve the KX250F’s cornering riddles by using Band-Aid fixes. The 2010 model was an improvement over the previous year, but it wasn’t anything to write home about. For 2011 Kawasaki reduced the fork offset from 23.5mm to 22.5mm and changed the material on the engine mount brackets. Also helpful is the ride height adjustment option on the forks. In turn, the 2011 KX250F corners inside any of the previous models, especially when the ride height and clickers are dialed in. No longer will you need to turn three times to navigate through a corner.

Q: WHAT DID WE DO TO MAKE THE KAWASAKI KX250F WORK BETTER?

A: Here is the list:

(1) Clutch springs. We roasted the stock clutch in 4-1/2 hours of riding. Kawasaki has always been known for having weak clutches. After turning the stock plates and fibers into molten lava, we tossed out the soft stock clutch springs and replaced them with stiffer Pro Circuit springs ($69.95, call (951) 738-8050). They did the trick.

(2) Forks. It’s not that we hate Showa’s new SFF system. Quite the opposite, actually. However, fast and/or fat riders will need to use a stiffer spring to maximize the performance of the forks.

Q: WHAT DID WE HATE?

A: The hate list:

(1) Shifting. Kawasaki revised their transmission by increasing the rotational angle of the ratchet for better gear engagement. They also reduced the tension on the return spring to match the longer shift stroke. The problem with the KX250F is that it doesn’t want to shift under a heavy load, especially from second gear to third.

(2) Clutch. The combination of a weak clutch and soft springs equates to a quick-slipping clutch. We opted for stiffer Pro Circuit clutch springs.

(3) Appearance. In brand-new condition, the 2011 KX250F looks sharp. However, after only a few hours of riding, the clutch and ignition covers are scratched, the black rims are pock-marked and the radiator graphics are peeled off. The KX250F doesn’t age well.

(4) Throttle grip. Kawasaki vulcanizes their cheap rubber grips to the plastic throttle tube and handlebars. This has been an annual pet peeve of test riders. Why? It’s very difficult to remove the stock grips. Forget the headache that comes with peeling off the throttle grip. Invest in an aluminum throttle tube. Problem solved.

(5) Cotter pin. The rear axle cotter pin is another pet peeve that has been bothering us for years. Instead of attending anger management classes, we simply replace the stock KX250F axle nut with a Honda self-locking nut.

(6) Brakes. The front and rear brakes are weak on the KX250F. We would like more pucker power.

(7) Capacitor location. Other manufacturers stow the capacitor for the EFI system out of harm’s way. The KX250F’s capacitor is located directly under the left side radiator. This is a very vulnerable place to house such an important part.

Q: WHAT DID WE LIKE?

A: The like list:

(1) Engine. Kawasaki pumped more peak ponies out of the KX250F engine thanks to several incremental camshaft, valve spring, piston and cylinder changes. Although the 2011 powerplant doesn’t surge through the midrange and into the top-end with as much vigor as the 2010 model, it’s still an effective race weapon.

(2) Fuel injection. Carbureted KX250F models had a habitual burp directly off idle that was annoying. That’s not the case anymore, thanks to a Keihin fuel injection system. The engine runs crisply and cleanly.

(3) Forks. Showa’s new Separate Function Fork is a technological marvel that will actually work once it gets the proper spring. The single spring rate is ballpark for most Novice 250F riders, but it really needs a stiffer spring is you plan to ride it hard. We opted for a heavier spring. Our favorite feature on the SFF forks was the ride height adjustment.

(4) Gearing. Guess what? Kawasaki finally figured out their gearing woes. The stock 13/50 combination works well on all but very tight tracks. Novice to Expert level riders all agreed that the 2011 KX250F is geared properly.

(5) Handling. The 2011 model is the best-handling KX250F that we have ever tested, but there is still lots of room for improvement.

Q: WHAT DO WE REALLY THINK?

A: Kawasaki targeted several problem areas on the KX250F and came away with a better handling, better suspended and crisper running bike. The caveat to this three-pronged approach is that the 2011 KX250F suffers in the area that every MXA tester loved?the powerband. Overall, the 2011 KX250F is better in some areas and worse in others?it’s a balanced trade-off.

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