KTM continues to roll out exciting new dirt bikes every year. Its entire full-size motocross lineup is completely revamped for 2023 with the addition of a new model that has captured the most limelight—the 300 SX. This open-class-worthy premix-burner features a combination of technology not seen on most two-stroke motocross models including throttle body injection (TBI), an electronic power valve, and electric starting. Before we publish our initial on-track evaluation of this exciting new model, let’s dig into its many features and specifications. KTM’s two-stroke motocross bike lineup grows by one in 2023 with the addition of the 300 SX. Mark Kariya Throttle body injection (TBI), an electronic power valve, and electric starting are huge technological advancements to the Austrian manufacturer’s all-new top-of-the-line two-stroke MX machine. Mark Kariya A Keihin 39mm throttle body is paired with case reed induction. Fuel needs to be premixed at 60:1. Mark Kariya Kickstarters are a thing of the past on KTM’s full-size two-stroke motocrossers. Claimed weight of the 300 SX engine is 53 pounds. Mark Kariya Engine start and engine stop buttons are combined on one unit, just within thumb’s reach. Mark Kariya On the opposite side of the Neken handlebar, we find the new engine map switch. Map 1 (white light illuminated) is standard, while map 2 (green light illuminated) is aggressive. Mark Kariya Proper airbox ventilation. Mark Kariya Gearing is 14/49. Mark Kariya KTM spec’d a new radiator cap on its 2023 full-size motocross and cross-country models that is quite difficult to remove. Mark Kariya The WP Xact 48mm air fork is the same component found on the Austrian manufacturer’s prior-generation (2019–2022) motocrossers, but features different settings and new hydrostops for better bottoming resistance. Mark Kariya Along with being 15mm shorter, the completely redesigned WP Xact shock features all-new internals. Mark Kariya Shock low-speed compression, high-speed compression, and rebound damping are adjustable by hand. Mark Kariya For reduced unsprung weight and increased rigidity, KTM designed a new, hollow, die-cast swingarm. Mark Kariya Brembo brake calipers help slow the smoker. The front is a two-piston caliper that grabs a 260mm disc, while the rear is a single-piston caliper that squeezes a 220mm disc. Mark Kariya We appreciate that KTM specs an hourmeter on all of its full-size motocross and off-road competition models to help keep track of maintenance intervals. Mark Kariya On Dirt Rider’s automotive scales, the 2023 KTM 300 SX weighs 232 pounds wet. Mark Kariya 2023 KTM 300 SX Specifications
Liquid-cooled, two-stroke single-cylinder
Bore x Stroke:
72.0 x 72.0mm
Dirt Rider Measured Horsepower: 48.8 hp @ 8,100 rpm
Dirt Rider Measured Torque: 32.2 lb.-ft. @ 7,500 rpm
EFI w/ 39mm throttle body
Wet, multiplate Damped Diaphragm Steel (DDS); hydraulic actuation
Central double-cradle chromoly steel
WP Xact 48mm fork, air pressure, compression damping, and rebound damping adjustable; 12.2 in. travel
WP Xact shock, spring preload, high-/low-speed compression damping, and rebound damping adjustable; 11.8 in. travel
Brembo 2-piston caliper, 260mm disc
Brembo 1-piston caliper, 220mm disc
Dunlop Geomax MX33; 80/100-21 / 110/90-19
Dirt Rider Measured Seat Height: 37.7 in.
Dirt Rider Measured Wet Weight: 232 lb.