Electronic fuel injection comes to the 2023 KTM SX line of full-size two-stroke MXers, along with many other changes, making these virtually all-new racebikes. The displacement mix is also new for 2023, with 300, 250, and 125 models—last year’s 150 is dropped in favor of an open-class 300. Let’s drop the gate and look at all the new features that the three models share.
Fuel injection by Keihin replaces the Mikuni TMX carburetor. The SXes don’t use the TPI (Transfer Port Injection) found in the EXC off-road models. Instead, it has a more traditional fuel injection setup with a 39mm throttle body. Unlike the TPI KTMs, the SXes run premixed fuel—60:1 on the 300 and 250, and 40:1 on the high-revving 125.
As before, the 300 and 250 share the same engine architecture, with the 125 having a 16-pound lighter design.
The power valve is now electronically, rather than mechanically, controlled. KTM claims this will create more mid-range power.
With EFI comes more electronic wizardry that’s new to KTM two-stroke motocrossers. There are two power maps, a throttle position sensor, improved idling, and a cold-start device. Should your ’23 SX hit the deck, a roll-over sensor kicks in to shut the motor down. Sorry, but the two-strokes don’t get the launch control, traction control, and quickshifter features that the four-strokes SX-F models boast.
The 2023 SXes all get electric starting. There is no kickstarter, and you can’t add one—push the button and go.
A new Pankl transmission is dropped into the cases. The 300 and 250 run a five-speed gearbox, while the 125 gets a sixth ratio. The DDS clutch is back with Brembo hydraulics.
The chassis is all-new—frame, subframe, swingarm, and WP suspension. The overall goal of the changes is improved rider comfort.
The frame has new parallel motor mounts to manage the frame’s rigidity. The new forged shock mount has the same goal.
KTM moved the footpegs in a bit. This will make scrubbing easier, and the pegs less likely to get hung up in ruts.
The frame is a combination of aluminum and polyamide. Over at the Husqvarna arm of KTM, the rear subframe has been polyamide and carbon fiber. This is a new hybrid design.
The new die-cast aluminum swingarm is hollow. Rigidity is increased while weight is dropped. There’s also a new rear axle to match the swingarm.
WP redesigned the Xact shock for the KTM SXes. The shorter body has all-new internals, and it weighs less.
A new hydrostop is dropped in the WP Xact air fork. This makes the fork less likely to bottom, per KTM. The damping settings have also been refined to reflect the changes in the frame.
The handlebar mounts get increased gripping surface. This will minimize bar twist in the roughest terrain.
Dunlop Geomax MX33 tires replace last year’s MX3S. The 125 has a 100mm wide rear tire, while the 300 and 250 run a 110. The new Dunlop tires are mounted on an Excel rim laced to CNC-machined hubs.
New angular bodywork reminds you of the significant changes to the KTM SX 300, 250, and 125. Also, it’s slimmer.
KTM has kept the MSRP of the 2023 KTM 300 SX, 250 SX, and 125 SX, well below $10k. The 125 SX is $7949, with the 250 SX bumping the price up to $8949, and the flagship 2023 KTM 300 SX wearing a $9199 price tag.
2023 KTM 300 SX, 250 SX and 125 SX Specs
Type: Single-cylinder 2-stroke
Displacement: 293cc (250: 249cc; 125: 125cc)
Bore x stroke: 72 x 72mm (250: 66.4 x 72mm; 125: 54 x 54.5mm)
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This week, in the first segment Editor Don Williams talks to us about the new Kawasaki Versys 650 LT. It’s the middleweight ADV style machine that uses the same 650 parallel twin motor as the Ninja 650, so it’s an excellent performer in a user-friendly, good looking package.
In the second segment, I chat with one of my dearest industry friends—now retired Honda PR executive, Jon Seidel. Jon’s fascinating career spans some 30 years with Big Red, and gave him some great experiences with some incredible machines. I was fortunate enough to be invited on many of the press launches that he organized. His new project is documenting and saving many of the old archives from years gone by—and incidentally, if you have anything that may be of value to the project, please contact us by email at firstname.lastname@example.org and we’ll pass it all on to Jon.
So on that note, from all of us here at Ultimate Motorcycling, we hope you enjoy this episode!