Courtesy of KTM

2019 KTM SX-F Models Announced

Learn about KTM’s 2019 four-stroke motocross bikes

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TM has released information about its 2019 four-stroke motocross models. The Austrian manufacturer’s four-stroke motocrossers, the 450 SX-F, 350 SX-F, and 250 SX-F, share the same suspension and chassis revisions and have a few model-specific updates to the engines, which we will begin with followed by the changes that are shared by all three of the 2019 machines.

KTM 450 SX-F
KTM’s flagship motocross bike, the 450 SX-F, features a more compact cylinder head that is both 15mm (approximately 0.6 inch) lower and 500 grams (just over 1 pound) lighter than the ’18 model.Courtesy of KTM

Engine

The changes made specifically to KTM's flagship motocross bike, the 450 SX-F, were focused on the cylinder head. It's more compact and is both 15mm (approximately 0.6 inch) lower and 500 grams (just over 1 pound) lighter than the '18 model. The camshaft surface has also been improved along with shorter valve timing for better responsiveness and new friction-reducing cam-chain guides. All of this is designed to provide a more efficient power delivery from the engine.

The 350 SX-F receives a reworked cylinder head design that features the same architecture as before but decreases weight by 200 grams (approximately 0.44 pound) compared to the previous models. The 350 SX-F and 250 SX-F both have new diaphragm steel (DS) clutches, and the other update to the 250 SX-F engine is the exhaust camshaft's new timing, designed to improve power delivery.

KTM 450 SX-F
All three of KTM’s four-stroke motocross bikes, the 450 SX-F, 350 SX-F, and 250 SX-F, now have new black frames designed to improve stiffness, specifically a 2-percent increase in longitudinal stiffness and a 10-percent increase in torsional stiffness.Courtesy of KTM

Each SX-F model is now fitted with new, model-specific header pipes that have a further-advanced resonator called a Flow Design Header (FDH). FDH is a small chamber around the pipe that slims the front part of the exhaust and provides better performance and reduced noise from the engine, according to KTM. Also, each of the four-stroke models now have Pankl transmissions designed to offer better durability than previous units.

The mufflers on each SX-F feature a new profile of the aluminum sleeve, new end cap, and a reworked internal design. KTM also increased the length of the connecting pipe of the muffler to move the connection between the header pipe and muffler farther forward. This makes removing and reinstalling the exhaust system easier because it can now be disassembled without removing the shock as was required on previous models, and it also allows for better access to the shock.

2019 KTM 350 SX-F
The 2019 350 SX-F receives a reworked cylinder head design that features the same architecture as before, but decreases weight by 200 grams (approximately 0.44 pound) in comparison to the previous models.Courtesy of KTM

The Keihin Engine Management System (EMS) on each SX-F model features a new 44mm throttle body, an improved seal on the Manifold-Absolute-Pressure (MAP) sensor designed to to increase reliability, and a reworked throttle cable mount that allows for better access and routing of the cables. Also, the ECU has new maps to work better with the new exhaust and cylinder head and provides different maps for optimal power characteristics for each gear according to the information received by the gear sensor.

The SX-F models have new lightweight lithium-ion starter batteries to decrease weight and provide quicker starting of the engine, especially in colder conditions. The packaging of the voltage regulator and condenser has been reworked to concentrate the electrical components in a common area below the seat and increase the reliability of the entire system. Further changes to the engines include reworked airboxes and intake snorkels and revised traction control and launch control settings.

WP AER 48 fork
The WP AER 48 fork on each SX-F model receives new damping settings.Courtesy of KTM

Suspension

In the suspension department, the WP AER 48 fork receives new damping settings while the WP shock features an updated main piston and new settings to match with the reworked fork setup and provide improved damping characteristics as well.

WP shock
The WP shock on the three SX-F models receive an updated main piston and new settings to match with the reworked fork setup and provide improved damping characteristicsCourtesy of KTM

Chassis

The chassis of each machine feature several changes including a new black frame with increased stiffness—specifically a 2-percent increase in longitudinal stiffness and a 10-percent increase in torsional stiffness. KTM did this to improve the feedback to the rider and offer more precise handling and increased straight-line stability. Protecting the updated frames are newly designed frame guards that feature a new surface to improve grip to the rider, and the right frame guard also serves as a heat guard for the muffler. Each SX-F now includes three brackets in the lower part of the frame to accommodate the addition of an optional composite skid plate sold through KTM PowerParts.

2019 KTM 350 SX-F
All three SX-F models have a stiffer upper triple clamp, a revised swingarm with a longer slot for the rear axle, and three brackets in the lower part of the frame to accommodate the addition of an optional composite skid plate sold through KTM PowerParts.Courtesy of KTM

Another part of the bikes that feature increased stiffness are the upper triple clamps. The revised units are designed to coincide with the stiffer frame and flex characteristics of the latest WP AER 48 fork in order to improve both handling and stability. The swingarm has also been revised and features a longer slot for the rear axle that allows the adjustment of the rear wheel to a position of up to 5mm farther back than before, which gives the rider the option to gain more straight-line stability for higher-speed tracks and obstacles such as whoops. Also, the subframes are 40mm (approximately 1.6 inches) longer to improve rear fender stability.

2019 KTM 250 SX-F
The 250 SX-F features a new exhaust camshaft with new timing designed to improve the power delivery.Courtesy of KTM

KTM also redesigned the radiators and mounted them 12mm lower than previous year models in order to lower the center of gravity. In the radiator area, a reworked coolant tube integrated in the frame triangle features a 4mm-larger center tube increasing the cross section by 57 percent, which makes coolant flow from the cylinder head to the radiators more efficient. The fuel tank has also been redesigned to improve ergonomics and the fuel pump assembly features an optimized internal routing of the hoses for greater reliability.

2019 KTM SX-F
Each SX-F model is now fitted with new, model-specific header pipes that have a further-advanced resonator called a Flow Design Header (FDH) and new mufflers with an updated profile of the aluminum sleeve, new end cap, and a reworked internal design.Courtesy of KTM

The final changes made to the chassis include new spoke nipples (designed to reduce the frequency of tightening spokes), new bodywork, a newly shaped seat, a reworked bar pad and cover, and new graphics. Lastly, all KTM motocross bikes now come with a new triangle stand that also serves as a spacer for the front wheel when tying the bike down for hauling in a vehicle. This reduces high static pressure on the air cartridge and prevents the fork from being compressed during transport.