MXA RACE TEST: THE REAL TEST OF THE 2021 KAWASAKI KX250

THE GEAR: Jersey: FXR Racing Helium, Pants: FXR Racing Helium, Helmet: FXR Racing 6D ATR-2, Goggles: Viral Brand Factory Series, Boots: Sidi Crossfire 3SR.

Q: FIRST AND FOREMOST, IS THE 2021 KAWASAKI KX250 BETTER THAN THE 2020 KX250? 

A: The easy answer is yes, but the 2021 KX250 isn’t all sunshine and rainbows. We were excited that the KX250 got the addition of electric starting and a hydraulic clutch for 2021, but without shedding weight on the KX250 to accommodate these components, the KX250 got 5 pounds heavier. That makes it 8 pounds heavier than the lightest bike in the class—the KTM 250SXF. It’s not the end of the world, however, as the RM-Z250, YZ250F and CRF250 are just as chunky. 

What we adored about the KX250 last year was its potent power. It produced the most horsepower in its class. Now, we have even more adoration for the 2021 KX250, as it kicked out the jams with an updated engine that makes even more pony power. All in all, the redesigned KX250 is a better motorcycle with a few chinks in its armor. 

The 2021 KX250 now has electric starting, hydraulic clutch, the KX450 chassis, and a more powerful engine.

Q: WHAT IS CHANGED FROM THE 2020 KX250 TO THE 2021 KX250 MODEL?

A: The biggest change would have to be the chassis. The 2021 KX250 adopted its big brother’s KX450 chassis. With that came an electric starter, hydraulic clutch, updated brakes and massaged Kayaba suspension. In 2020, Kawasaki revamped the entire KX250 powerplant. For 2021, the engineers made some key changes to improve durability and power. We are going to bring into focus the 2021 engine changes. 

(1) Connecting rod. The connecting rod was lengthened by 3mm to decrease side loads on the cylinder walls as the piston moves up and down. Long-rodding the engine helped reduce mechanical losses. 

(2) Piston. The 2021 piston crown was changed from a domed piston to a flat-top piston to give the engine more character on the top end. 

(3) Crankcase. The left upside crankcase was revised to house the hydraulic clutch, while the right-side case was reshaped due to the removal of the kickstarter gear assembly. 

(4) Crankshaft. The updated crankshaft looks very different from what you normally see. Instead of two full-circle counterbalance weights on each side of the connecting rod, the weights have been cut down to almost half circles. This was done to reduce weight, allowing the engine to rev faster and to improve durability at high rpm. 

(5) Cylinder head-valve ports. The intake and exhaust ports were machined with a new process that Kawasaki was very tight-lipped about. Before, each head had to be polished by hand to smooth out the rough spots after CNC machining. This updated process saves time and money, as there is no need for hand-polishing anymore. The ports have also been reshaped to improve performance. 

(6) Cams and cam chain. The cam’s design remains the same, but the cam’s sprocket teeth have been widened and the cam chain has been enlarged by 2mm to ensure durability. The cam timing was also retarded 3 degrees. 

(7) Valve springs. The valve springs were made stiffer to handle the high-rpm thrashing. 

(8) Belleville washer. For 2021, the KX250 not only received a hydraulic clutch, like the KX450, but also a Belleville washer spring system that replaces the individual clutch springs. This is virtually the same spring system that KTM and Husky have been using for years. It’s about time other manufactures caught on. It works. 

(9) Clutch plates. The friction plates feature three types of material (compared to one friction compound in 2020) and also have offset segments that reduce drag and promote clean separation. 

Even though the 2020 KX250 engine was all-new last year, Kawasaki didn’t rest on their laurels for 2021. This engine is more powerful on every part of the curve.

Q: HAS THE PRICE CHANGED WITH ALL THE UPDATES TO THE 2021 KX250?

A: Yes, the addition of electric starting and a hydraulic clutch upped the retail price by $500 to $8299. We expected this. Every other manufacturer that has added these premium items raised its prices as well. As it sits, the 2021 KX250 is tied with the 2021 YZ250F as the third most expensive bike behind the KTM 250SXF and FC250. 

Q: IS THIS 2020 HORSEPOWER CLASS WINNER MORE POWERFUL IN 2021?

A: The updated Kawasaki powerplant made the KX250 more powerful across the entire rpm spectrum. It revs further, offers more peak power and improves its poor bottom-end performance. This engine can be characterized as a pure-bred race engine. Why? Because you can’t be lazy on it. You need to ride the KX250 like a 125cc two-stroke. We aren’t kidding. To get the most out of the KX250 powerband, you need to rev the engine until it peaks and shrieks. Don’t worry, it doesn’t take very long to get there. With the lighter crank, it races through the midrange to get to its high-rpm sweet spot. You just need to be ready for it. 

If you ride the KX250 like you’re going out for a Sunday stroll, the orange, white and blue competition will blow by you due to the KX250’s lackluster bottom-end power. Yes, the bottom-end power has been improved, but only from poor to mediocre. Serious racers shouldn’t worry too much about the KX250’s run-of-the-mill low-to-mid transition, because if you’re really serious, what are you doing down there anyway? It took some time for the MXA test riders to adapt to staying in the meat of the powerband, which was way up there. The big difference was that they had to shift a lot, so much so that our fastest MXA test riders were getting into first gear to ensure they were getting the most out of the bike. 

Don’t get us wrong, the 2021 KX250 is very powerful. On race day, it will go neck and neck with the YZ250F, FC250 and KTM 250SXF, as it still offers the most peak horsepower in the class; however, to do that, the KX250 needs to be ridden very differently from the other three. If you have 125cc two-stroke experience, you’re off to a great start.  

The Kayaba KX250 shock is just like last year, perfect.

Q: HOW DID THE KX250 POWERPLANT WORK IN THE KX450 CHASSIS?

A: We have to say that the KX250 engine looks minuscule in the KX450 chassis. Other than that, the transition into the updated chassis was almost seamless. The KX250 handled much like the KX450. The chassis felt thin and agile, even though it packed on 5 additional pounds due to the electric starter and battery. 

The KX250 offered incredible straight-line stability and traction. The front end did feel on the high side to our test riders. It had a similar feel to the 2012 through 2016 chassis. This made the front end feel very light, which wasn’t helpful on flat or off-camber corners, as the front end wanted to push. We tried sliding the forks up in the clamps and raising the sag to put more weight on the front, but these changes had adverse effects on the handling. 

If the track is soft or rutty, the KX250’s light front-end issues are minimized. If you get forward on the bike on the entrance of corners, the bike will turn in easily. When you do it right, the KX250 slices through a corner like a knife in warm butter. If you don’t move up on the tank, the bike will stand up at the apex of the corner. The front end, which has a larger front axle to increase rigidity, seems to track straighter and more precise once in a rut. Upon exit, it feels like the rear of the bike does most of the work. The rear wheel digs into the terra firma to launch you out of the corner. We think these are side effects of the KX450 chassis more than something inherent in the KX250’s geometry.

Overall, we have mixed feelings about the chassis. It does so many things really well, but the one thing it does poorly is provide confidence in its handling. 

Q: HOW DID WE LIKE THE KAYABA SUSPENSION?

A: If we are talking about the shock, it is amazing. It does nothing wrong. It tracks the ground like glue. It absorbs chop exceptionally well and does nothing out of the ordinary. It is everything a shock should be. The suspension settings are tailored for 103mm of sag. We went down to our normal 105mm, but we lost more than we gained at the front end. The rear actually handles better at 105mm, but the overall chassis balance was thrown off. 

The forks are where our complaints start. On a positive note, the first part of the fork’s stroke is supple, and the last part of the stroke ramps up to easily handle really big hits. The problem lies somewhere in the middle. The valving ramps up too fast too soon from the middle to the bottom of the stroke. If we went out on the clickers, the forks would drop into the harsh part of the stroke, making them feel stiff. When we went stiffer, the forks rode higher in their stroke but couldn’t access enough travel to get the most out of the forks. We were at a dead end. We are not saying these are bad forks; we just feel they miss the mark. 

To Band-Aid the issue, we could have lowered the oil height or gone down on the spring rate (from 4.9 N/mm springs to 4.8 N/mm)—although this wouldn’t solve the steep ramp-up curve of the fork’s valving. If you want to get the best out of these forks, send them to your favorite suspension tuner. We are biased towards Pro Circuit, as they know more about these Kawasaki forks than anyone in the business.  

The KX250 Showa forks are its weak spot for 2021. They ramp up too fast creating a harsh spot we can’t seem to get rid of. We lowered the oil height by taking out 5 to 10cc of oil.

Q: HOW WAS THE MAPPING OF THE THREE COUPLERS?

A: What we liked about the three KX250 couplers was that they each served a different purpose. They were all distinctly different from each other, which is what adjustable maps should strive to be. If you don’t know which coupler is which, listen up. The green coupler is stock. The black coupler is mellow, and the white coupler is aggressive. Although, we wouldn’t call any of the couplers mellow for 2021. The black coupler offers the most aggressive low-end power. It just signs off earlier than the other two. MXA test riders could hit corners in second gear when they were using first with the other two couplers. The white coupler was the most aggressive from mid to top-end, although we felt that the engine decompression braking was excessive. The stock green coupler was middle of the road. 

We wanted a map that combined the best of the aggressive white coupler, without its heavy decompression braking, with the perky low-end of the black coupler. Kawasaki’s top tuner, Mike Chavez, brewed us up some concoctions with the Kawasaki FI calibration kit ($699.95). After a few different maps, he hit pay dirt when he combined the ignition timing of the aggressive map with the fuel flow of the mellow map. They went together like white on rice. This custom map gave the KX250 more snap off the bottom without sacrificing anything on top. It was a recipe for success. 

These are the fuel settings from the stock mellow map that we combined with the ignition settings from the aggressive map.
The ignition setting.

Q: DID WE CHANGE THE STOCK GEARING?

A: Yes. The stock gearing had our MXA test riders in first gear in tight corners—not that being in first gear is the end of the world, but it is by no means a plus when a bike has to go down to first gear to get proper drive. Case in point, being in first gear had the MXA test riders shifting right when they were exiting the corner. It is tough to get the shift point down when you are only going to be in that gear for a split second. We went up one tooth in the rear—from the stock 51 to a 52. This helped tremendously through the corners and getting from gear to gear quicker. The only downfall was having to shift more, but never out of first gear.

Q: WHAT DID WE HATE?

A: The hate list. 

(1) Seat bolts. Every time you take off the seat bolt, the back plates fall on the ground. This gets annoying. 

(2) Chain roller. The front chain roller starts to wear down after 5 hours. At 10, it will start to come apart. Order a TM Designworks chain roller. And while you’re at it, order a chain guide as well, because at 15 hours you will need one. 

(3) Decibels. This is a very loud bike. The only way it will pass sound regulations is if there aren’t any. 

(4) Forks. These forks have a harsh spot you can’t run away from unless you get them re-valved. 

(5) Chassis. The front-end geometry is too high, making the front-end want to push. We tried putting more weight on the front by raising the forks in the clamps, but that brought up other handling issues. 

Q: WHAT DID WE LIKE?

A: The like list.

(1) Ergonomics. The narrow chassis makes you feel at home on the bike. If you don’t feel at home, the pegs and bars mounts are adjustable.  

(2) Maps. We liked that each of the three maps was distinctly different from the others and each worked. 

(3) Shock. We love the Kayaba shock. We just wish the forks worked as well.

(4) Engine. Kawasaki made improvements to the high rpm where it needed it. This is an engine that hardcore racers will love. 

(5) Brakes. The updated brakes are great. 

(6) Bars. Kawasaki finally went with a bigger bar diameter like the rest of its competition. We like the Renthal Fatbars.

To get the most out of the 14,500 rpm engine you must ride it like a 125cc two-stroke, wide open.

Q: WHAT DO WE REALLY THINK?

A: The 2021 KX250 is a much better bike than the 2020 model. It offers electric starting, a bulletproof hydraulic clutch and a powerful high-rpm engine. To get the most out of it, you must ride it at the top of its 14,500-rpm rev range. If we had a complaint, it would be the forks. They ramp up too fast. Many racers send their suspension to their favorite tuner before they even ride the bike. We recommend riding it first so that you can check your suspension tuner’s bona fides.  

MXA’S 2021 KAWASAKI KX250 SETUP SPECS 

This is how we set up our 2021 Kawasaki KX250 for racing. We offer it as a guide to help you find your own sweet spot.

KAYABA FORK SETTINGS
The KX250 Kayaba forks are supple at the top of the stroke, which works great on smooth tracks. When the KX250 hits rougher tracks, there is no way around the mid-stroke harshness, short of breaking into the internals. We took out 5 to 10cc of oil to break through the hashness. For hardcore racing, we recommend this fork setup for the 2021 Kawasaki KX250 (stock specs are in parentheses):
Spring rate: 4.9 N/mm
Compression: 8 clicks out (12 clicks out)
Rebound: 12 clicks out (11 clicks out)
Fork-leg height: Standard
Notes: On rough tracks, the softer you go, the further the forks will drop, hitting the harsh part of the stroke. We went a few clicks stiffer to ride above the harshness. 

KAYABA SHOCK SETTINGS
MXA test riders love this shock. We went back and forth from 105mm of sag to 103mm. We found a better overall setup at 103mm, which is Kawasaki’s standard setting. At 103mm, the MXA test riders felt the rear would kick at times, but two clicks in on rebound resolved the issue. For hardcore racing, we recommend this shock setup for the 2021 Kawasaki KX250 (stock specs are in parentheses):
Spring rate: 54 N/mm
Race sag: 103 mm
Hi-compression: 1-1/2 turns out
Lo-compression: 10 clicks out
Rebound: 13 clicks out (15 clicks out)
Notes: You will find comfort on this shock within a couple clicks in either direction.

MXA FIRST RIDE VIDEO: 2021 KAWASAKI KX250

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