advrider Posted May 17, 2022 Share Posted May 17, 2022 KTM’s SX two- and four-stroke lineups see several changes for 2023. KTM says its SX bikes “…are the most innovative and high-performing ready to race production motocross bikes ever built.” That’s a pretty big claim, so let’s look at the Austrian manufacturer’s 2023 SX bikes. SX Frame All SX bike frames receive “major” updates. KTM says the new structure improves overall dynamics, anti-squat behavior, and stability. The enhanced performance comes from the repositioning of rotating masses in the frame combined with thicker frame walls, a forged steering head connection, and an all-new shock mount. For 2023, the mount is no longer connected to the main frame tube. The 2023 two-stoke models also get new parallel frame mounts which KTM says improve the frame’s flex characteristics. The SX lineup also gets repositioned footrest mounts. KTM has moved them inward, saying that the new positioning makes them less susceptible to hooking in deep ruts or scrubbing jumps. That said, KTM the footrests are now 26 percent larger than their predecessors. The new footrest design comes from state-of-the-art finite element analysis (FEA). FEA uses computerized calculations to predict “…how a product reacts to real-world forces, vibration, heat, fluid flow, and other physical effects.” KTM says the changed footrests and footrest positioning dramatically improve comfort and control when standing on the pegs. Suspension For 2023, the SX bikes’ 48mm XACT fork gets new “hydro stops” in the fork legs. KTM says that the hydro stops provide better bottoming out resistance and improve progressive damping in the last 40mm of the fork’s travel. The result is said to allow “…the fork to stay lower and more planted on initial acceleration after a hard landing. The fork also provides quick adjustment via a single air pressure preload valve. And now, the air pump necessary to adjust its air pressure is included as standard. Setting compression and rebound is handled via easy access quick adjusters. Ergonomics The 2023 SX bikes get multiple updates that support the rider triangle by providing better knee contact, especially when standing on the pegs. KTM says that more contact surfaces on the bike’s bodywork improve overall handling, agility, and confidence. There’s also a new orange high grip seat cover that KTM says offers “exceptional control” in all weather conditions. There’s also a recessed pocket under the seat above the airbox that provides a clean air intake. Lastly, a newly designed front fender now incorporates mud fins. The fins are said to offer exceptional ability to dispel and redirect dirt and mud away from the rider and the bike’s radiators in wet conditions. KTM’s four-stroke SX lineup There are also model-specific changes to KTM’s four-stroke lineup for 2023. While some changes are minor, KTM has redesigned some crucial components which it claims up the four-stroke SX lineup’s capabilities. The 2023 KTM 250 SX-F. Photo: KTM The 2023 KTM 350 SX-F. Photo: KTM The 2023 KTM 450 SX-F. Photo: KTM Cylinder heads The KTM 450 SX-F, 350 SX-F and 250 SX-F each get redesigns to their engine’s cylinder heads. The 450 SX-F gets redesigned intake ports, which allow higher flow coefficients that result in a more efficient and powerful engine. Going down one step, the 350 SX-F features a fully redesigned dual overhead cam (DOHC) finger followers with DLC coating to reduce friction. The powerplant’s new 29.1 mm exhaust valve delivers an optimized gas flow, and valve timing is adapted to work in conjunction with a redesigned camshaft. The smallest sibling in the KTM four-stroke lineup, the KTM 250 SX-F offers a fully redesigned DOHC cylinder head. It also has a redesigned camshaft bearing bridge which is screwed down to increase stiffness. Gearbox The bike’s gearbox has been redesigned and features a lightweight 5-speed gearbox by Pankl Racing Systems. The new design focuses on a “weight-optimized” shift shaft that KTM says reduces the operating forces of gear changes. Quickshifter A new quickshifter function can be activated or deactivated using a new map select switch, allowing clutchless upshifts while the throttle is fully open. This is possible through the use of a sensor on the shift drum. It measures the force on the shift lever and, when appropriate, sends a signal to the ECU to retard the ignition timing. KTM’s two-stroke SX lineup According to KTM, the two-stroke range receives the “…biggest spread of advancements in the 2023 Motocross lineup.” The changes aim to benefit usability and performance. The 2023 KTM 300 SX. Photo: KTM The 2023 KTM 250 SX. Photo: KTM Electronic fuel injection For the first time, the “full size” KTM SX range is equipped with electronic fuel injection. Working with Keihin, a 39 mm throttle body was developed in conjunction with a specially tuned ECU from Vitesse. KTM says the setup always delivers the correct air-fuel mixture by constantly analyzing water temperature, air temperature, ambient pressure, crankcase pressure, rpm, and throttle position. The bike’s newly designed injectors also provide optimal burn rates and produce a finer fuel spray for cleaner ignition and more efficient fuel use. Reed valve The two-stroke machines benefit from what KTM says is a crucial design update to the valve reed case. It now has added plastic flaps on the outside of the reed valve case for better sealing of the entire intake tract. The new design is said to negate over-fueling in extreme up or downhill sections. This ensures that there is no bogging down or running rich. Engine maps Now that the two-stroke models get EFI, KTM can introduce two different engine maps. The maps can be easily toggled with handlebar mounted switchgear. KTM says 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. Exhaust The entire KTM SX range gets a more compact exhaust header design that improves ground clearance. The silencer has also been made smaller and is crafted from “lightweight” aluminum. Electric start For 2023. KTM has introduced an electric start on the entire SX range of motorcycles. The bike’s starter motor does not have an intermediate shaft which saves some weight and permits a compact engine design protected from roost. Powering the new setup is a 12.8V 2 Ah lithium-ion battery placed under the seat close to the bike’s center of gravity. KTM 300 SX KTM’s most powerful two-stroke machine is the 300 SX. According to the Austrian manufacturer, the bike is aimed at racers looking for “…maximum power with the least possible weight. The new engine kicks out a claimed 57 hp and has an overall claimed weight of about 52 pounds (23.9 kg). The combination gives the new 300 SX an impressive power-to-weight ratio, which KTM says is designed to provide more torque than any previous two-stroke engine while maintaining a high-revving, lightweight two-stroke character. Vezi sursa Quote Link to comment Share on other sites More sharing options...
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