2018 KTM 125 SX
The whip cracking KTM 125 SX has been at the front for years. With phenomenal performance on tap, it will be there for many more seasons to come. A compact chassis and the lowest weight out there is teamed up with a high performance 125cc 2-stroke engine for a surefire trophy collection. Get shredding, youngsters.
- Engine: The latest KTM 125 SX engine is the most powerful and most competitive engine in its class; a clear statement that KTM is keen on keeping 2-stroke technology at the forefront of development. The secret to their success is an outstanding power-to-weight ratio, low costs and simplicity. This 125cc ripper has been developed with the latest KTM engineering know-how and the most advanced technology available. The results: class-leading power across the rev range, while being extremely compact and ultra-light at a mere 39.5 pounds. Our work here is done; now it’s up to you to collect the trophies.
- Cylinder: This compact cylinder with a 54mm bore features a cutting-edge power valve unit with a sophisticated mechanism for the lateral support exhaust ports. Matched to a twin-component cylinder head, it is KTM’s secret to all-round grunt. The layout of the water jackets in the cylinder and head guarantees efficient heat dissipation when the going gets tough.
- Crankcases: For the latest engine generation the KTM engineers designed lightweight die-cast engine cases featuring a high crankshaft position located close to the center of gravity, which results in optimal mass centralization and outstanding rideability.
- Crankshaft: This reliable piece of engineering has been skillfully balanced to guarantee minimal vibrations. In its latest form, it allows an increase of the displacement to 144cc just by replacing cylinder, piston and head. There’s no longer the need to change the crankshaft if you want to change displacement. Two-in-one in no time.
- Transmission: A robust 6-speed transmission was designed specifically for the small 2-stroke engine, its gear ratios are perfectly in sync with the 125’s power band. The latest production technologies allow for compact dimensions and minimal weight. An advanced ´No Dirt´gear lever design prevents mud from clogging the folding tip for reliable shifts even in the worst conditions.
- Carburetor: The KTM 125 SX is fitted with a MIKUNI TMX carburetor. This 38mm flat slide carb lives to provide smooth and controllable power all the way up to the rev limitation. With a new intake manifold the carburetor is turned 7° in order to reduce the overflow of fuel. And it’s less sensitive to different altitudes and temperatures, so you can pin it wherever, whenever.
- Exhaust: The engineers meticulously tuned the expansion chamber for maximum torque and power, so this screamer is as tough as it is strong.
- Ignition: All 2-stroke models feature a new CDI control unit with an advanced hardware which improves the starting behavior of the engine. The ignition curves remain unchanged.
- Weight: The main target for the KTM engineers when developing the SX models was a massive weight reduction compared to the previous generation. The result: the current SX models are the slimmest, lightest bikes on the track.
- Frame: The high-tech, lightweight chrome-moly steel frame has a knack for easy handling, outlandish rideability, precise cornering and excellent stability. You can also count on high torsional rigidity and low longitudinal stiffness. This results in better absorption of the energy created from the front and rear suspension, sucking up jumps and bumps. In short: more comfort and less rider fatigue. Laterally attached, engine head stays (the connection between cylinder head and frame) are now made of lightweight aluminum. They contribute to more precise cornering and a reduced vibration level. The engineers were able to pull off all that, while making their frame 2.2 pounds lighter than that of the lightest competitor on the market. In addition, it is easier to maintain, easier to work on and supplies more space for the tank and other components. The bike also features an extra-light subframe made of aluminum, which tips the scales at less than 2 pounds.
- Footpegs: Sophisticated ´No Dirt´ footpegs prevent clogging of the footpeg pivot, even when digging in deep ruts. Looking for a higher riding position? Then just mount the footpegs of the MY2017 EXC models, which are 6mm higher than the SX versions.
- Air Filter Box: The airbox design offers maximum protection of the air filter while ensuring maximum airflow. The large twin-air filter is mounted in a stiff cage, which at the same time holds the system in place. This design is so simple you could still pop a fresh one in with a face full of mud. Without tools. In seconds.
- Handlebar: KTM engineers sure know how to handle handlebars. This tapered unit, made of high-strength aluminum, is fixed in damped rubber mounts and has two different positions.. ODI lock-on grips make grip changes easy and do not require any wire or glue to be secured.
- Swingarm: The cast aluminum design offers low weight and a perfect flex behavior. The single-component casting process eliminates any inconsistencies and inherent weak points created by welding. It’s better looking as well.
- Fuel Tank: A lightweight polyethylene tank with a capacity of 1.85 gallons. The fuel tank cap has an inside thread, which makes for easy and reliable closure.
- Wheels: Featuring lightweight, CNC machined hubs and high-end Excel rims, they guarantee maximum stability and minimal unsprung weight. The wheels are shod with the latest Dunlop Geomax MX 3S tires.
- Cooling System: KTM’s proven cooling system routes the coolant from the cylinder head through the frame triangle, directly to aluminum radiators made by WP. A new filler cap system and are stiffer alloy construction increase the durability and reliability of the cooling system. Due to flow optimized internal circulation and CFD-calculated air ventilation, the system is superbly efficient. In addition, well thought-out radiator guards integrated in the front part of the shrouds provide protection in a crash.
- Bodywork: KTM R&D, Kiska Design and the factory racers had their say in shaping the plastics with one goal: complete harmony between rider and bike. Perfect ergonomics and contact points provide maximum comfort in movement on the SX-F. The I-beam structures of the front and rear fenders guarantee maximum stability and a low weight thanks to well thought-out construction and mounting. They also stay cleaner for longer.
- Graphics: New graphics convey the READY TO RACE character of the SX model line.
- Shock Absorber: The WP shock absorber has been developed with the entire frame and swingarm architecture in mind, including the linkage and the WP AER 48 front fork. It features machined and black anodized components and is a valuable, high-end product compared to roughcast reservoirs. A new, confidence inspiring setting with improved damping characteristics perfectly matches the front-end setup and its WP color scheme lets everyone know you have excellent taste in suspension.
- Fork: The lightweight WP AER 48 front fork, a 48mm USD air-sprung fork developed by WP in close collaboration with KTM, is a split fork with separate functions for each leg. That means damping functions are on the right side, whereas the air spring is in the left. This left leg features a 2-chamber system with a capsuled air cartridge to prevent loss of air pressure. Should the outer seal start to leak, the internal cartridge pressure will keep the bike in position. The air spring is easy to adjust to any rider weight via a single air valve. No special tools are required; the fork air pump is supplied with the bike. The right fork leg integrates a damping cartridge that tailors to all your damping needs. It can be adjusted to the track conditions and the rider’s preferences with a twist of a dial (compression from the top, rebound from the bottom, 30 clicks each). Right off the dealer floor, this fork (with reworked damping characteristics) is more comfortable and more sensitive than ever. But you can still hammer the hell out of it.
- Triple Clamp: Top quality, CNC machined triple clamps have been a KTM trademark for years to ensure precise handling. For 2017, the upper triple clamp specifically features a redesign in conjunction with the new fork tubes. The rubber damped handlebar mount has also been reworked and the lower handlebar clamps are now separated, while on the upper side a new bridge-type clamp guarantees more torsional stiffness and can easily be replaced in case it gets twisted due to a crash. In addition, a hourmeter is fitted at the upper triple clamp in order to let the rider know it’s time for a service.
- Brakes: You can’t brake any harder, better, faster or stronger. These high-tech Brembo babies are combined with lightweight wave discs made by Galfer. For 2017, the rear brake features a 10mm longer brake pedal and you get new, less aggressive brake pads all round.
- Design: 1-cylinder, 2-stroke engine
- Displacement: 124.8 cm³
- Bore: 54 mm
- Stroke: 54.5 mm
- Starter: Kickstarter
- Transmission: 6-speed
- Primary drive: 23:73
- Secondary gear ratio: 13:50
- Clutch: Wet multi-disc clutch, Brembo hydraulics
- EMS: Kokusan
- Frame design: 25CrMo4 steel central-tube frame
- Front suspension: WP-USD, AER 48, Ø 48 mm
- Rear suspension: WP shock absorber with linkage
- Suspension travel (front): 12.2 in.
- Front brake: Disc brake
- Rear brake: Disc brake
- Front brake disc diameter: 260 mm
- Rear brake disc diameter: 220 mm
- Chain: 5/8 x 1/4 in.
- Steering head angle: 63.9 deg.
- Seat height: 37.8 in.
- Weight READY TO RACE (pound) (without fuel): 192.24 lb.
- Suspension travel (rear): 11.81 in.
- Tank capacity (approx.): 1.85 US gal.
- Engine Type
- 1-cylinder, 2-stroke engine
- 124.8 cm³
- Bore and Stroke
- 54 x 54.5 mm
- Front Suspension
- WP-USD, AER 48, Ø 48 mm
- Front Brakes
- Disc brake
- Rear Suspension
- WP shock absorber with linkage
- Rear Brakes
- Disc brake
- Dry Weight
- 192.24 lb.
- Fuel Capacity
- 1.85 US gal.
- Seat Height
- 37.8 in.
- Final Drive
- Chain: 5/8 x 1/4 in.