2023 KTM SX Two-Strokes
After a few years without any major changes to the drivetrain, KTM have given the SX models a thorough update for the new model year.
Expected to arrive in Australia this November (2022)
The senior two-stroke KTM motocross range spans the 125, 250 and 300 cc categories in 2023.
Gone is the 38mm Mikuni TMX carburettor and in its place is a new 39 mm throttle body along with a new reed-valve case design across all three models.
The two-stroke motocrossers don’t use the same TPI electronic fuel injection system that has long been standard fitment on the KTM two-stroke enduro bikes.
While the enduro bikes sport a separate oil tank, and the bikes mix the oil/fuel themselves, the motocross machines still require riders to pre-mix the fuel, for which KTM specify a 60:1 mix ratio.
This is because enduro bikes in many countries, such as ours, are required to pass emissions tests and that can only be achieved these days with the oil injection systems we have on the enduro range. Closed course competition machines such as these SX models have no such requirement. We believe the system that is used on the 2023 KTM SX motocross bikes is of the more direct design that we have seen being used by many of the Factory KTM enduro racers for some time now.
KTM claim more than 57 horsepower from the 300 SX from an engine that tips the scales at less than 24 kg.
This is a couple of ponies less than what we have seen from some recent 250 two-stroke KTM motocross machines that boasted quite a ferocious power delivery. For the 2023 model year with fuel-injection the focus has clearly switched to putting that power to the ground.
The 250 and 300 models have a claimed weight (without fuel) of 99.4 kg, while the 125 is a featherweight 92.4 kg. All bikes use a 7.2 litre fuel cell.
The 300 and 250 are identical and both sport a 72 mm stroke but the 250 slides through a 66.4mm bore while the 300 runs 72 x 72 mm bore/stroke dimensions. The 125 is also quite square with a 54.5 mm stroke and 54 mm bore and that engine weighs less than 18 kg.
Oh to be fit and fast enough to do one justice…
The 2023 KTM SX range will count on 2 maps (one standard, soft and linear power, and another for a more aggressive response). However, while their four-stroke siblings get a quick-shifter for 2023, the two-stroke models do not get this feature.
Electric start is standard and powered by a lithium ion battery that is charged by a new stator.
The latest spec’ WP suspenders now offers tool-free adjustments at both ends. Both high and low speed compression on the shock can be easily adjusted, while up front a single air-pressure pre-load valve makes changes quick and easy combined with click adjusters for compression and rebound on the 48 mm WP XACT forks.
The WP Suspension XACT shock is shorter and lighter. KTM claim the internal flow of liquids is more flush, reliable and resistant, and that the shock’s smaller dimensions lower the chances of pollutants and dirt intrusion.
The shape permits higher ground clearance with the linkage and advanced damping means better traction as the bike ingests the bumps with new geometry.
The KTM SX two-strokes have new parallel frame mounts. KTM claim the design is sportier with designers sights set on extra agility; an example comes through the new inwardly moved footpegs for even greater clearance in ruts and for dropping the bike flat for jump scrubs.
New foot-pegs are larger in surface area, even if the die casting means they are lighter than before.
Stiffness has been dialed with lighter die cast hollow swingarms (new casting processes allow for even more weight saving) and a new rear axle. The Excel rims sport an improved nipple design.
The 2023 KTM SX two-stroke models expected are expected to arrive in Australia from November 2022.
