KTM 50SX: FULL TEST

Our youngest test rider Jacob Tilley having some fun on the 2018 KTM 50SX.

KTM’s 2018 50SX is the first step on the evolutionary ladder for tomorrow’s off-road enthusiasts. It boasts a lot of similarities to the larger race and off-road models in KTM’s lineup. As a matter of fact, it’s probably best described as a scaled-down version of what you see raced by KTM’s professional factory racers around the world.

KTM’s 50SX powerplant is very similar to the larger two-strokes in their lineup.

CHASSIS

Styling comes straight from the full-size SX models, complete with a gripper seat with no tools needed for removal, aluminum handlebars and KTM grips. Just like the full-size machines, the 50SX is designed to provide comfortable ergonomics with well-thought-out contact points for the rider and maximum freedom of movement.

The frame is produced by WP Performance Systems and is made of lightweight, high-strength chromoly steel, just like all the other models in KTM’s off-road lineup. This frame is designed to combine maximum longitudinal stiffness with optimum torsional rigidity for precise cornering without sacrificing overall stability.

The 50SX has all the styling and features of the larger bikes in KTM’s line up including an air fork, disc brakes, hydraulic clutch, Maxxis tires and no tools required to change the air filter.

KTM’s 50SX is the first model in its class fitted with a modern, fully adjustable air fork. WP’s new AER 35 is a newly developed upside-down front fork with a 35mm tube diameter and 205mm of travel. It is 1.6 pounds lighter than the previous spring model. Another benefit of the AER 35 is the adjustability. Adding or subtracting the amount of air pressure via the provided fork pump allows the fork to be tuned to accommodate a wide range of riders.

The adjustable rear shock is designed to work without linkage and is rebuildable. Notice the two different mounting options on the frame. The one not being used provides a higher stance for taller riders.

In the rear, a WP shock is mounted directly to the swingarm with no linkage—similar to what is offered on KTM’s XC-W line of off-road models. The WP unit provides damping performance and is fully adjustable to riders’ preferences and track conditions. The rear-wheel travel is 185mm. Like the big KTM factory racers, the 50SX has lightweight, black-anodized aluminum rims wrapped with Maxxis tires.

Designed to fit a wide variety of riders, the KTM’s 50SX power delivery can be toned down or increased for more aggressive pilots quickly and easily by merely adjusting the clutch.

ENGINE

KTM’s 50SX features a 49cc engine equipped with a liquid-cooling system with one large radiator that not only keeps the top-end temperature down but also cools the crankcase, just as on the larger SX models. A high-performance cylinder is designed to work in conjunction with the exhaust and reed intake system fed by a Dellorto carburetor. A centrifugal multi-disc automatic clutch provides manageable acceleration. It can be adjusted to the specific requirements of the track or rider’s needs by turning three 8mm-head adjustment bolts.

The seat can easily be removed and the air filter accessed by unlocking the Zues fastener located by the rear fender. The seat is made of a non-slip material.

The triple clamp allows up to four different bar mount settings.

BOTTOM LINE

The 2018 KTM 50SX is truly a scaled-down version of the larger SX models in KTM’s lineup. It offers the same type of adjustability across the board for rider comfort and overall performance. The AER 43 fork can be adjusted to fit a wide variety of riders, and the two different shock mounting positions on the frame help balance out the machine when drastically changing fork settings. The power delivery can be dialed in pretty easily for beginners or advanced riders by adjusting the automatic clutch. The only bummer is taking off the OEM clutch cover to access the adjustment screws.

One of the venues where we tested the 50SX was the Big 6 GP at Primm, Nevada.

KTM Hard Parts offers a billet-aluminum cover to remedy this problem. During testing, we did notice that the lighter we went on clutch engagement, the more often the plates and oil needed to be changed. If your rider is a true beginner, KTM offers a power reduction kit that is very effective. The KTM 50SX is a great machine for a wide variety of riders, although it can be a bit on the tall side, and the price tag of around $4000 can be a shocker. If your rider is on the smaller side, the 50SX Mini might fit him better, and it’s about $500 less expensive.