Technology: KTM's 2023 four-stroke models
This week we already profiled the new two-strokes from KTM and now it is the turn of the machines from their four-stroke range. They also received a major update with many technical novelties that require some explanation.
Even though the four-stroke KTMs are still at the top of their segment, it has been six years since they received a major update. The engine in particular had remained virtually unchanged all these years and in order to maintain their lead over the competitors, a major update was now introduced.
The machines from Austria look very slick and sleek, you can't fault them in terms of design because the orange engines are very sleek. But design doesn't win races, so a lot has changed underneath. We took a closer look at all the novelties of the 2023 four-stroke models.
Frame
The hydroformed, laser-cut and robot-welded frame has undergone significant updates to improve overall dynamics and stability. This is partly due to the repositioned rotating masses in the frame and the forged headset connection, in combination with an all-new shock absorber mount, which is no longer connected to the main frame tube. Thicker frame walls also contribute to improved reliability and specific stiffness in highly stressed areas such as the steering head and shock absorber mounts.
A major highlight of the new frame is the repositioned footpeg mounts. These have been moved inwards, making them less likely to get stuck in deep ruts or when scrubbing. However, the overall size of the footpegs has increased by 26%. The frame of the 2023 KTM SX-F models is finished with a black powder coating and a hard-wearing matte surface. Additionally, black frame protectors with a new and improved grip structure are standard, ensuring superior protection, durability and ultimate grip.
Subframe
Weighing just 1,815 kg, the new two-piece polyamide-reinforced aluminum subframe delivers impressive weight savings. Using FEA, carefully calculated stiffness has been built into the subframe, providing excellent handling and feedback, whilst remaining robust and reliable. The subframe design also provides a neat housing for all electronics, keeping them safe, dry and out of the way.
Swingarm
A new hollow cast aluminum swingarm is designed to provide optimal stiffness and reliability at the lowest possible weight. The topology is optimized for stiffness, while an improved casting process reduces weight by approximately 190 g. A new 22mm rear axle has also been fitted which is tailored to the new bending characteristics of the chassis.
Motor
The four-stroke engines also received a complete update. Perhaps the most important change is that the engine has been rotated two degrees backwards. On the 2023 KTM 250 SX-F the position of the block is also slightly lowered. This means the four-stroke benefits from improved mass centralization, which drastically improves driving dynamics and stability during acceleration.
Another point of interest of the new 2023 KTM SX-F range is its ease of maintenance. Fluid drain noses and added service markings on the engine (▲) clearly indicate where the washers should be used, making maintenance and service easier and more accessible for different levels of riders.
The 450 SX-F's newly designed SOHC cylinder head is incredibly compact and light, with a short profile with the camshaft positioned as close to the center of gravity as possible. The revised intake ports provide a higher flow coefficient, resulting in a more efficient and powerful engine.
The completely redesigned DOHC cylinder heads of the 350 SX-F and 250 SX-F feature finger followers with a DLC coating, resulting in minimal friction and optimal performance.
Gear box
A newly designed 5-speed gearbox by Pankl Racing Systems guarantees the highest level of durability and reliability. The redesign is centered around a weight-optimized shift shaft, reducing operating force when shifting.
When the engine is idling, launch control is activated by pressing the Traction Control and Quickshift buttons simultaneously. This function regulates the amount of power to the rear wheel when starting off, improving traction and preventing wheelspin under hard acceleration.
The traction control is set to an on or off position at the switch and works by analyzing the rider's throttle input and the rate at which the engine revs increases. If the revs increase too quickly, the ECU senses a loss of grip and reduces the amount of power to the rear wheel to ensure maximum traction. This provides a clear advantage in poor traction, dusty hardpack surfaces or in wet or muddy conditions.
Quickshifters
The new Quickshifter function can be activated or deactivated via the new map select switch, allowing clutchless upshifts with the throttle wide open. A sensor on the shift drum registers the force on the shift lever, sends the signal to the ECU, which briefly interrupts the ignition. To prevent unintentional shifting and false neutrals, the function is only active from 2nd to 5th gear. This function can also be disabled if desired.
Suspension
The 48mm XACT fork has new hydro stops in the fork legs, making the fork more resistant to bottoming. The split-air fork features an encapsulated air spring and pressurized oil chamber for progressive and consistent damping. These oil and air bypasses reduce pressure peaks and provide exceptional feedback and rider comfort.
As with the shock absorber, easy and quick adjustment is of the utmost importance. This is done via the single air pressure preload valve and via easily accessible click adjusters for the compression and rebound damping. In addition, the air pump required to adjust the fork's air pressure is included as standard.
An all-new rear shock absorber results in a reduction in overall length and weight compared to the previous generation, while suspension travel remains unchanged at 300mm, with an emphasis on easy adjustment without tools or strip-downs.
A new CFD optimized main piston improves comfort, while differently sized flow holes allow the shims to open more easily and reduce the overall stress of oil flow and pressure on the shims for an overall smoother operation.
Adjustability is now taken care of by a hand-adjustable dual compression control knob, allowing quick and easy adjustment of high and low speed settings. Combined with the newly designed rebound adjuster, which can also be adjusted by hand, riders can adjust their shock absorber settings without tools and without the help of a mechanic in the pits.
A new spring preload adjuster has also been introduced, providing greater resistance to dirt ingress, and a new two-piece spring retainer that allows quick installation without splitting the shock absorber.
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