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2021 Kawasaki KX250 Project Bike | Track Tested



Dirt Bike TV KX250

The 2021 Kawasaki KX250 was almost unanimously awarded our Bike of The Year honors in the 250F division, and for good reason. Slim ergonomics, excellent straight-line stability, strong cornering and a playful engine all cumulatively add up to an awesome package that on the whole, is tough to beat. However, we love tinkering with bikes and trying to find a little more out of even the best package.

We enlisted the help of our long-time buddy Jay Clark of Dirt Bike TV to try to coax even more fun out of our KX and per usual, he did not disappoint.

One of the only flaws in the Kawasaki powerband is a that it is a top-end based power plant. It revs high into the RPM’s and needs to be ridden aggressively to keep it there. This results in a somewhat vulnerable low-end. Don’t get us wrong, the power of the KX is excellent, but small mistakes down low leave us susceptible to falling off the power and having to play catch-up with a few stabs at the clutch. A new Vortex ECU massaged with some influence by Jamie at Twisted Development offers an incredibly quick snap right from the crack of the throttle. That, mated with a Vertex high compression piston to add some depth and torque that the stock configuration lacks made in incredible difference out on the track. Rather than needing to attack every corner to keep the KX singing, we could approach the turns with more creativity in line selection knowing that we now had more punch and more grunt to pull us out of the corners. The low-end feels significantly more substantial and bridges the gap into the KX’s strong mid-range much more seamlessly than stock. The mid-range pulls hard! It is impressive how well it attacked the steep hills of Glen Helen without any flat spots on the way to strong top-end we love so much about the Kawasaki. While the low-end got the biggest benefit, the entire power curve was improved dramatically.  

The stock Kawasaki suspension is great in stock form in that it offers a plush feel and consistent action. A lot of our test riders felt it could benefit from firmer settings – especially our larger riders. Jay enlisted the help of Schmidt Performance to tackle the handling aspect and we must say, we were very impressed. In fact, while adding some much needed firmness to the KX and good bottoming resistance, the Schmidt Performance suspension was some of the plushest we have tested in resent years. Great mix of performance and comfort. As we have come to expect from Jay, the bling factor was nearly as impressive as the performance gains making the Kawasaki almost as cool to look at as it is to ride.

If you are looking for a little more performance out of your KX, consider following Jay’s lead… we were impressed.

For this build we kept it very simple with no engine porting etc—  we just added a Vertex High Compression piston and a Vortex ECU with a FMF pipe.   The Stock pipe is annoying loud and the FMF really helps that.   
Vertex Pistons                  
High Compression GP Racer Piston kit  (rings, DLC pin and clips)  
Twisted Development 
Vortex ECU
Cometic Gasket     
Top-End gaskets
Schmidt Performance                     
Suspension Re-Valve and set up 
Rear Sprocket  
Front Sprocket  
Gold MX Race Chain G520-MXT-L-120
Uni Filter                              
Two-Stage air filter                     


Hinson Clutch Components                    
Clutch plates and outer cover


FMF Racing                              
Full Megabomb header with RCT 4.1 Muffler                            
Dunlop Tire                             
MX33 Front Tire
MX12 Rear Tire


Works Connection                            
Brake Caps 
Works Stand II
Brake Rotating bar mount
Engine plugs 
Axle Blocks 
Oil Filter Cover 
Pro-Launch Holeshot device
DeCal Works                                     
Semi-Custom Graphics kit in Sparkle                    
Pre printed number plates backgrounds in Sparkle 
Graphic Guards (protects side # Plate graphics)
UFO Plastic  
Full plastic kit  
Mud Flap   
Rear Chain guard


P3 Carbon   
P3 X-Series .7lb Carbon Skid plate-   


Moto Seat                               
Custom Cool seat cover
Titanium Footpegs  
MX V2 Lock On Grips
CFT Podium MX Handle Bars  – Champ Bend 
Fire Power 
FeatherWeight Lithium Battery
Klotz Lubricants     
Oils & Chemicals 
VP Fuel 
T4 Fuel  


Chase Curtis

Chase Curtis is an avid motocross and MTB rider, and he has been editing moto videos for a mere two years. He's also the Swapmoto Race Series on-site photographer and reporter. When he finishes college, he will join the SML staff full time.

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1 Comment

  1. Andrew Allen July 29, 2021

    What front and rear supersprox were you running? I can’t find any for my kx. Thanks