150 SX 2021
KTM 150 SX 2021 for Sale at KTM Epping in Epping, VIC | Specifications and Review Information
WIDE OPEN TRACK ATTACK
With the agility of a 125 and a healthy dose of extra power, the KTM 150 SX is a lively package ready to take on the 250 cc 4-strokes. From within its dynamic lightweight chassis, the compact engine produces class-leading torque and power. Everything about this motorcycle screams high-performance fun and it goes into battle as the ultimate on-track competitor.
The pure exhilaration that this bike's engine delivers warranted continued production. As it shares many of its key components with the class-leading 125, the cylinder, cylinder head and piston unit can now also be fitted on a 125 cc engine base, converting it to a 150 SX without having to replace the crankshaft. Compact and powerful, this innovative 2-stroke engine is a lightweight powerhouse that just makes perfect sense.
At the heart of the 150 cc engine is a 58 mm bore cylinder. It features an innovative power valve unit with a sophisticated mechanism designed for the lateral support exhaust ports. The exhaust port layout enhances engine performance, while the precise machining of the upper contour of the exhaust port ensures accurate port timing. The two component cylinder head works in complete harmony with the cylinder to deliver outstanding performance across the entire rev range.
CRANKCASES AND ENGINE COVERS
The lightweight engine cases are manufactured using a high pressure die-cast production process, keeping wall thickness to a minimum while retaining strength and durability. The design allows for a high crankshaft position which is located near to the center of gravity, resulting in optimal mass centralization and easier rideability. The engine body is extremely compact, which contributes significantly to the low engine weight.
The KTM 150 SX is fitted with a robust 6-speed transmission. The gear ratios, which featured improvements and reinforcements, were carried over from the predecessor. The gearbox features a new drive shaft which uses a screw for front sprocket fixation and diaphragm spring instead of a circlip, ensuring optimal front sprocket fixation. Another highlight of the 150 SX transmission is the no-dirt gear shifter. Similar to the footpeg design, it prevents the build-up of dirt and ensures the next gear is always available, no matter what the conditions.
The KTM 150 SX is fitted with a MIKUNI TMX 38mm flat slide carburetor that for 2021 is matched with a new throttle assembly with roller actuation. The recently reworked reeds for intake reed block provide further improvements in function, sealing and reliability, ensuring the whole system is always providing smooth, controllable power throughout the rev range.
The crankshaft has a 54,5 mm stroke that produces the optimal torque and revs. It has been ideally balanced and with the counter balancer shaft, results in minimum vibration. The crankshaft is placed in the perfect position to centralize mass, contributing to better agility and handling.
Maintaining the optimal engine temperature is crucial to ensuring consistent horsepower throughout the ride. The KTM 150 SX features radiators which are positioned for a lower center of gravity. Their design matches the shrouds perfectly and offers a great slim feel to the ergonomics. By using CFD technology (computational fluid dynamics) together with a clever coolant circuit routing, the innovative system ensures the optimum engine temperature for the highest performance, no matter what the conditions. The radiators also feature special protectors that serve not only as protection from flying rocks and debris but also as a brace that disperses energy around the radiators in the event of an impact.
When it comes to power delivery and performance, the exhaust developed specifically for this bike plays a key role and packs a punch that is hard to beat. In addition, its special shape provides slimmer ergonomics while still operating safely within the noise limits for racing.
The frame is professionally crafted from hydro-formed chromium molybdenum steel tubes that are robot welded, ensuring the highest levels of consistent quality. The stiffness has been precisely tailored for the most dynamic handling, and works in perfect harmony with the suspension to provide nimble agility without losing high-speed stability. The frame also features no dirt footpegs, which have a simple but effective self-cleaning system that ensures the footpegs return to their original position, providing complete control in all conditions. All SX frames feature the same highly durable powder coating as the KTM Factory machines and come with standard frame protectors. The subframe is made from lightweight aluminum, providing rear fender stability and strong support for the rider at little extra weight.
The one-piece swingarm is manufactured using a gravity die-cast production process for exceptional strength at the lowest possible weight. It offers a wide range of adjustment for the rear wheel, allowing for a shorter wheelbase on tighter, twisty tracks, or a longer wheelbase for greater stability on longer, more choppy tracks. The swingarm's chain measurement markings are visible from above, making adjustment simpler and more accurate.
KTM uses lightweight, CNC-machined hubs and high-end Excel rims on all SX models, guaranteeing maximum stability and minimum weight. The aluminum spoke nipples feature a design that conveniently reduces the frequency with which the spokes need to be tightened. The wheels are fitted with the latest Dunlop Geomax-MX33 tires, delivering maximum grip and stability, effectively transferring all the power to the ground.
All full-size KTM SX models are fitted with the super-lightweight WP XACT fork with AER technology. It is a 48 mm USD air-sprung fork with separate functions in each fork leg, with damping functions on the right side and the air spring on the left. The left leg features a two-chamber system with a capsuled air cartridge, helping prevent loss of air pressure. Essentially, this means that in the rare case of a leaking outer seal, the internal cartridge pressure keeps the bike in a normal position. The air spring is exceptionally easy to use and can be adjusted to any rider weight via a single air valve and the air pump that is supplied with the bike. The right fork leg integrates a damping cartridge to fit single damping leg requirements and can be adjusted to the track conditions and the rider's preferences. Additionally, the fork top caps have a new design for improved, easy adjustment (compression from top, rebound from bottom, 30 clicks each).
All KTM SX models feature a WP XACT monoshock, which has been developed to work as a complete unit with the entire frame and swingarm architecture, as well as the linkage system and the WP XACT fork. It features high-quality machined and anodized components, which add a touch of class and give it appeal beyond just a functional necessity. It is fully adjustable, including high and low speed compression, allowing you to set the shock up precisely to suit any track and rider's preferences.
All KTM SX models feature top quality, CNC-machined triple clamps which have become a KTM trademark. The triple clamp has a precisely calculated stiffness and offset (22 mm offset for all models) to match the flex characteristics of the frame and fork. The result is a front end that works in perfect harmony, contributing positively to the overall handling and stability. The rubber damped handlebar fixation reduces vibration and also allows for some adjustment with two different mounting positions. An hour meter is fitted as standard on the upper triple clamp on all SX models, keeping the rider informed of the number of hours spent tearing up the track and when the next service is due.
High-tech Brembo S.p.A brakes have always been standard equipment on all KTM motocross bikes. Combined with lightweight wave discs, the renowned system provides the highest level of braking efficiency, enabling you to out-brake the competition.
All models in the KTM SX range are fitted with lightweight polyethylene fuel tanks. The shape of the fuel tank allows for slim ergonomics without compromise to the 7 liter fuel capacity. The filler cap has an inside thread that makes for easy and reliable closure.
The airbox on the KTM 150 SX ensures optimal flow dynamics, and together with its intake snorkels, leads to maximum power and quick throttle response. Despite the obvious performance advantages, the design also offers maximum protection against soiling of the air filter. The large Twin-Air air filter is mounted on a cleverly designed stiff cage that minimizes incorrect installation. As found on previous models, filter maintenance is quick and easy and does not require tools - a standard, original feature from KTM.
All KTM SX models feature a seat that perfectly matches the range's dynamic performance-oriented ergonomics. The seat cover features silicone strips that provide better feel and grip for the rider. The seat is conveniently fixed to the bike using one long, lateral screw, making it easy to handle.
All full-size KTM SX models are equipped with the same high-strength aluminum tapered handlebar, made by NEKEN. The handlebar is fixed in rubber damped mountings, which allow for two different positions. The handlebars come standard with an ODI vulcanized grip on the right side and a comfortable ODI lock-on grip, which does not require any wire or glue, on the left. They also feature a bar-pad with a cover that can be attached and removed with little effort.
Sophisticated 'no-dirt' footpegs prevent smudging up the pegs, even when digging in deep ruts. Looking for a higher riding position? Then just mount the footpegs of the KTM 2018 EXC models, which are 6mm higher than the SX versions.
The new graphics suit the aggressive nature of the bike and further enhance the high performance look of the bodywork.
Multi-plate clutch, Brembo hydraulics
1-cylinder, 2-stroke engine
Weight (Without Fuel)
Tank Capacity (Approx.)
Front Brake Disic Diameter
Rear Brake Disic Diameter
5/8 x 1/4"
Central double-cradle-type 25CrMo4 steel
WP XACT-USD, Ø 48 mm
WP XACT Monoshock with linkage
Steering head angle
Suspension Travel (Front)
Suspension Travel (Rear)
The illustrated vehicles may vary in selected details from the production models and some illustrations feature optional equipment available at additional cost. All information concerning the scope of supply, appearance, services, dimensions and weights is non-binding and specified with the proviso that errors, for instance in printing, setting and/or typing, may occur; such information is subject to change without notice. Please note that model specifications may vary from country to country.
The consumption values stated refer to the roadworthy series condition of the vehicles at the time of factory delivery.