Tested - Race Tech Kawasaki KX250 Project Bike

Modern day 250 four strokes are quite amazing, really. But at the same time, the latest batch of updates that some brands have handed down has really pushed the power up-stream in their 250s, leaving behind some of the bottom-to-mid grunt that 250Fs had. Got corner speed and want to ring the bike's neck / throttle? Then it's all good! Want to be a little lazier and short shift them? Then you'll notice these changes a bit. Kawasaki's latest version of the KX250 has gone through this process, gaining the top-end to rival the Austrian machines but losing some of the response and forgiveness their outgoing engine had. This, along with a solid suspension setting was the main reason we turned our Team Green over to Race Tech for a little love.

Upgrades from Race Tech:

• Ported and polished cylinder head
• Epoxy port work
• Copper beryllium valve seats - $850 for all the Cylinder Head Work Combined
• Race Tech spec one piece titanium valves
• Race Tech spec valve springs
• Vortex ECU with custom mapping for VP MR Pro 6 and T4 - $275 for Custom Mapping
• Re-spring front and rear suspension
• Revalve front and rear suspension with Race Tech Gold Valves

Upgrades from other Brands:

• Full FMF 4.1 RCT titanium exhaust system
• Pirelli MX32 90/100-21 front tire
• Pirelli MX32 110/90-19 rear tire
• VP T4 race fuel
• ERA Moto - Custom Graphics Kit

In the Shop

As for the work to the bike itself, we wanted to keep the list small and focus on a couple key items. The majority of the upgrades were done by Race Tech, with a few finishing items from other brands thrown in. Race Tech's first stop was the engine. After disassembling the cylinder head; it was ported and polished, along with some epoxy work to the intake port side to meet what they felt like the KX needed. The head also received new copper beryllium valve seats so they could be modified to the extent required in this spec. This machine also received a custom one piece valve of Race Tech's own spec, along with a valve spring kit to maintain control and reliability. After re-assembly, we added a full exhaust system from FMF. Their 4.1 RCT and Megabomb header mostly added for some mid-range punch and help the bike rev a bit quicker. Lastly for the engine side, the KX got a little dyno time and a dialed in Vortex ECU with custom mapping for both VP Racing's T4 and Pro6 fuel options. We primarily wanted to run the bike on T4.

As for the suspension, Race Tech installed their Gold Valve system and with a new setting, along with upping the spring rates front and rear for my somewhat over the stock target weight. The bike was capped off with a pair of Pirelli MX32 Mid-Soft tires and a simple / clean graphics kit from ERA Moto. Outside of this, we left everything else stock. The gearing, bars, grips, pegs, wheels... Heck, even the seat cover!

On the Track

A good chunk of the modded 250 four strokes I've ridden in the past few years are a bit better everywhere when compared to their stock counterpart. In this case, yes, this bike is a bit better everywhere but it's also heavily improved when it comes to the low-to-mid performance. In stock trim, the latest KX250 is a screamer. The harder and longer you can keep that throttle on, the more rewarding it is...very KTM-esque. Race Tech's spec for this bike is a bit better up top, but it gets up and moving way earlier. The stock bike feels lethargic at lower RPMs, lacks recovery character, and just overall takes its sweet time to get into the higher Rs. The RT spec however is snappy, responsive, and gets up and out of bed in a hurry. Although I went with stock gearing, there was enough of a difference here to consider going either way and make further gains on the track. Going up a tooth would make third usable in so many situations, as the engine changes alone swapped me from second-to-third in quite a few corners. Or going down a tooth to stretch second back out as now the bike builds power quick enough that second gear was a bit too aggressive in the tighter corners and tended to snap loose on exits if the throttle wasn't applied with some thought behind it. Overall, this was one of the bigger engine character changes I've experienced from a modded 250, so hats off to Race Tech.

As for the suspension, my main concerns were getting the rear shock stiff enough to match the more aggressive character of the front forks. Eliminating some of the wallowing and bringing back some confidence so I could push the rear of the bike through rollers and more abrupt jump faces. Race Tech nailed this and out front they gained quite a bit of comfort. The stock KX250 forks have quite the harsh point stock, regardless of what settings or balance I attempted out of the box. RT's setting relieved quite a bit of this, making it much easier to ride over a longer moto and not adding as much wear and tear on the upper body. If I'm being totally honest, there were some small sensations of that harshness so with further riding I'd keep tuning a little bit to see if we could totally eliminate it. But to Race Tech's credit, they took away about 85-90% of that complaint.

Last Words

For quite a while, the goal with 250Fs was just to get more power everywhere but these days they're pretty darn good in certain areas. Well, enough for most. However depending on your riding style and preferences, there can always be improvements. From our experience, Race Tech does a solid job of making gains in usable places and improving the overall riding experience of almost any machine. This Kawasaki is no exception. Reach out to them to find out what they have available for your ride and how they can improve your experience.

For the original video we did on this project bike, click play here.