First Look - 2023 KTM 125, 250, and 300 SX Two Stroke Models 8

KTM has gone all-in for their latest batch of two stroke motocross bikes. New chassis, new bodywork, heavily revised engines, fuel injection, electric start and a 300 moto model! Read below for the latest.

The 2023 KTM 2-stroke SX range sees the return of the KTM 125 SX and wildly popular KTM 250 SX, with a new Open Class entry in the form of the KTM 300 SX. The 2023 KTM 2-stroke SX range enjoys the biggest spread of advancements in the 2023 Motocross line-up, with benefits aimed at usability and performance - not to mention bringing 2-stroke technology into the modern MX era. 

ELECTRONIC FUEL INJECTION  

For the first time, the full-sized KTM SX range receives electronic fuel injection across the range.  

Together with Keihin, a 39 mm throttle body was developed to withstand the harsh and full-throttle demands of competitive motocross. This is done by a specifically tuned ECU from Vitesco, works in conjunction with the Keihin throttle body to always deliver the correct air-fuel mixture by constantly analyzing water temperature, air temperature, ambient pressure, the pressure within the crankcase, rpm, and throttle position.  

Newly designed injectors also work to provide an optimal burn rate, with improved Sauter mean diameter (SMD), producing a finer spray of fuel for a cleaner ignition and less fuel wastage.  

Overall, the 2023 KTM SX range provides riders with a real-world alternative to 4-strokes, offering optimal power delivery in any condition without the need to rejet carburetors.

REED VALVE  

The reed valve case has received an important design update, with newly added plastic flaps on the outside of the reed valve case for better sealing of the entire intake tract. This new design negates over-fueling in extreme up- or downhill sections with no bogging down or running rich.  

Boyesen continues to supply the carbon membranes for the reed valve case.

ELECTRIC POWER VALVE

With the introduction of EFI, the power valve is controlled according to the throttle position and engine RPMs. Being auto-calibrating, there’s no more hassle with incorrect power valve adjustments, with the EMS calculating the ideal position automatically. This results in linear and predictable power delivery at all throttle inputs.

EXHAUST

The 2023 KTM SX range benefits from a more compact exhaust header design, achieving improved ground clearance, reducing the risk of any damage from deep ruts, or external objects. The silencer also benefits from the compact treatment, crafted from lightweight aluminum, and stylishly finished off in a premium black coating.

ENGINE MAPS   

With the addition of EFI, it was possible to introduce different engine maps on the 2-stroke SX range, easily toggled via the handlebar switchgear. Map 1 provides a standard, more mellow map for linear, predictable power, while Map 2 is more aggressive, with immediate throttle response and a more crisp, explosive power output.

ELECTRIC START

Another new addition to the 2023 KTM SX range, is electric start which is easily toggled via a newly designed combined Start/Stop switch on the right side of the handlebar,  

The starter motor comes without any intermediate shaft, saving weight and allowing a compact engine design with perfect integration and protection from roost. Weight-saving has gone even further, with an ultra-lightweight 12.8V 2 Ah Lithium-Ion battery placed under the seat close to the center of gravity.  

KTM 300 SX  

The most powerful 2-stroke weapon in the KTM SX stable, the KTM 300 SX enters the race as a new choice of firepower into the MX Open category. 

Aimed at racers looking for maximum power with the least possible weight, the 2023 KTM 300 SX offers simplicity and low maintenance. With massive power-, and an overall weight of just 52.6 lb, the new 300 SX engine sets the benchmark when it comes to power to weight ratios, and is designed to provide more torque than any previous 2-stroke engine without losing its typical high-revving lightweight 2-stroke character.

2023 KTM 125 SX HIGHLIGHTS

• All-new generation model with new chassis and engine wrapped in new bodywork. 
• New engine with electronic power valve offers improved mid-range power and rotating mass.
• New 39 mm Keihin throttle body features advanced EFI technology for immediate throttle response and ease of use—no more jetting for conditions. 
• New electric start and lightweight Li-Ion battery provide immediate starts at a light weight.
• New frame design with parallel mounts, new forged shock mount and reworked rigidity to better manage rider comfort. 
• New topology optimized subframe with hybrid polyamide and aluminum construction for improved durability.   
• New hollow, die-cast swingarm offers reduced unsprung weight and increased rigidity. 
• Updated WP XACT fork with new settings and new hydrostop to improve bottoming resistance.
• New, completely redesigned WP XACT rear shock has a lighter and shorter body and all new internals. 
• New topology optimized handlebar mounts increase grip surface for reduced bar twist. 
• New map select switch changes engine character depending on track conditions and rider preference.
• Hydraulic Brembo clutch system offers highly controllable modulation and light operation.
• High-tech Brembo brakes combined with lightweight wave discs offer incredible braking power and feel.
• CNC machined hubs and high-end Excel rims combine unmatched performance and durability with massive weight savings. 

SPECIFICATIONS

• Engine Type: Single Cylinder, 2-Stroke
• Displacement: 124.8 cc
• Bore / Stroke: 54 / 54.5 mm
• Starter: Electric starter / Lithium Ion 12.8V 2Ah
• Transmission: 6 Gears
• Fuel System: Keihin EFI, throttle body 39 mm
• Lubrication: Premix 40:1
• Primary Ratio: 23:73
• Final Drive: 13:51
• Cooling: Liquid Cooling
• Clutch: Wet Multi-Disc DS Clutch, Brembo Hydraulics
• Ignition: Vitesco Technologies EMS
• Frame: Central Double-Cradle Type 25CrMo4 Steel
• Sub Frame: Aluminum reinforced Polyamide
• Handlebar: Neken, Aluminum Ø 28/22 mm
• Front Suspension: WP XACT USD Fork, Ø 48 mm 
• Rear Suspension: WP XACT Monoshock with Linkage
• Suspension Travel Front/Rear: 310 / 300 mm; 12.2 / 11.81 in
• Front/Rear Brakes: Disc Brake 260 mm / 220 mm
• Front/Rear Rims: 1.60x 21” / 2.15 x 19” Excel
• Front/Rear Tires: 80/100-21” / 100/90-19” Dunlop MX33
• Chain: 5/8 x 1/4 in
• Silencer: Aluminum
• Steering Head Angle: 26.1º
• Triple Clamp Offset: 22 mm
• Wheelbase: 1,493 mm ± 10 mm / 58.7 ± 0.4 in
• Ground Clearance: 359 mm / 14.1 in
• Seat Height: 958 mm / 37.7 in
• Tank Capacity, Approx: 7.2 L / 1.90 gal
• Weight (without fuel), Approx: 92.4 kg / 203.7 lbs

2023 KTM 250 SX HIGHLIGHTS

• All-new generation model with new chassis and engine wrapped in new bodywork. 
• New engine with electronic power valve offers improved mid-range power and rotating mass.
• New 39 mm Keihin throttle body features advanced EFI technology for immediate throttle response and ease of use—no more jetting for conditions. 
• New electric start and lightweight Li-Ion battery provide immediate starts at a light weight.
• New frame design with parallel mounts, new forged shock mount and reworked rigidity to better manage rider comfort. 
• New topology optimized subframe with hybrid polyamide and aluminum construction for improved durability.   
• New hollow, die-cast swingarm offers reduced unsprung weight and increased rigidity. 
• Updated WP XACT fork with new settings and new hydrostop to improve bottoming resistance.
• New, completely redesigned WP XACT rear shock has a lighter and shorter body and all new internals. 
• New topology optimized handlebar mounts increase grip surface for reduced bar twist. 
• New map select switch changes engine character depending on track conditions and rider preference.
• Hydraulic Brembo clutch system offers highly controllable modulation and light operation.
• High-tech Brembo brakes combined with lightweight wave discs offer incredible braking power and feel.
• CNC machined hubs and high-end Excel rims combine unmatched performance and durability with massive weight savings.

SPECIFICATIONS

• Engine Type: Single Cylinder, 2-Stroke
• Displacement: 249 cc
• Bore / Stroke: 66.4 / 72 mm
• Starter: Electric starter / Lithium Ion 12.8V 2Ah
• Transmission: 5 Gears
• Fuel System: Keihin EFI, throttle body 39 mm
• Lubrication: Premix 60:1
• Primary Ratio: 26:72
• Final Drive: 14:49
• Cooling: Liquid Cooling
• Clutch: Wet Multi-Disc DDS-Clutch, Brembo Hydraulics
• Ignition: Vitesco Technologies EMS
• Frame: Central Double-Cradle Type 25CrMo4 Steel
• Sub Frame: Aluminum reinforced Polyamide
• Handlebar: Neken, Aluminum Ø 28/22 mm
• Front Suspension: WP XACT USD Fork, Ø 48 mm 
• Rear Suspension: WP XACT Monoshock with Linkage
• Suspension Travel Front/Rear: 310 / 300 mm; 12.2 / 11.81 in
• Front/Rear Brakes: Disc Brake 260 mm / 220 mm
• Front/Rear Rims: 1.60 x 21” / 2.15 x 19” Excel
• Front/Rear Tires: 80/100-21” / 110/90-19” Dunlop MX33
• Chain: 5/8 x 1/4 in
• Silencer: Aluminum
• Steering Head Angle: 26.1º
• Triple Clamp Offset: 22 mm
• Wheelbase: 1,493 mm ± 10 mm / 58.7 ± 0.4 in
• Ground Clearance: 354 mm / 13.9 in
• Seat Height: 958 mm / 37.7 in
• Tank Capacity, Approx: 7.2 L / 1.90 gal
• Weight (without fuel), Approx: 99.4 kg / 219.1 lbs

2023 KTM 300 SX HIGHLIGHTS

• All-new model with new chassis and engine wrapped in new bodywork. 
• New engine with electronic power valve offers improved mid-range power and rotating mass.
• New 39 mm Keihin throttle body features advanced EFI technology for immediate throttle response and ease of use—no more jetting for conditions. 
• New electric start and lightweight Li-Ion battery provide immediate starts at a light weight.
• New frame design with parallel mounts, new forged shock mount and reworked rigidity to better manage rider comfort. 
• New topology optimized subframe with hybrid polyamide and aluminum construction for improved durability.   
• New hollow, die-cast swingarm offers reduced unsprung weight and increased rigidity. 
• Updated WP XACT fork with new settings and new hydrostop to improve bottoming resistance.
• New, completely redesigned WP XACT rear shock has a lighter and shorter body and all new internals. 
• New topology optimized handlebar mounts increase grip surface for reduced bar twist. 
• New map select switch changes engine character depending on track conditions and rider preference.
• Hydraulic Brembo clutch system offers highly controllable modulation and light operation.
• High-tech Brembo brakes combined with lightweight wave discs offer incredible braking power and feel.
• CNC machined hubs and high-end Excel rims combine unmatched performance and durability with massive weight savings.

SPECIFICATIONS

• Engine Type: Single Cylinder, 2-Stroke
• Displacement: 293.2 cc
• Bore / Stroke: 72 / 72 mm
• Starter: Electric starter / Lithium Ion 12.8V 2Ah
• Transmission: 5 Gears
• Fuel System: Keihin EFI, throttle body 39 mm
• Lubrication: Premix 60:1
• Primary Ratio: 26:72
• Final Drive: 14:49
• Cooling: Liquid Cooling
• Clutch: Wet Multi-Disc DDS-Clutch, Brembo Hydraulics
• Ignition: Vitesco Technologies EMS
• Frame: Central Double-Cradle Type 25CrMo4 Steel
• Sub Frame: Aluminum reinforced Polyamide
• Handlebar: Neken, Aluminum Ø 28/22 mm
• Front Suspension: WP XACT USD Fork, Ø 48 mm 
• Rear Suspension: WP XACT Monoshock with Linkage
• Suspension Travel Front/Rear: 310 / 300 mm; 12.2 / 11.81 in
• Front/Rear Brakes: Disc Brake 260 mm / 220 mm
• Front/Rear Rims: 1.60 x 21” / 2.15 x 19” Excel
• Front/Rear Tires: 80/100-21” / 110/90-19” Dunlop MX33
• Chain: 5/8 x 1/4 in
• Silencer: Aluminum
• Steering Head Angle: 26.1º
• Triple Clamp Offset: 22 mm
• Wheelbase: 1,493 mm ± 10 mm / 58.7 ± 0.4 in
• Ground Clearance: 354 mm / 13.9 in
• Seat Height: 958 mm / 37.7 in
• Tank Capacity, Approx: 7.2 L / 1.90 gal
• Weight (without fuel), Approx: 99.4 kg / 219.1 lbs

View key specs, compare bikes, and rate the new KTM SX models in the Vital MX Product Guide.