KTM 125 SX

Although KTM has been offering motocross models for much longer, it was not until 1993 that the series received the SX designation. A name that inevitably recalls the legendary US racing series Supercross, which also uses the abbreviation SX. To win there, you need an extremely powerful machine, both in terms of the chassis and the engine. These characteristics fit perfectly with the brand's slogan, Ready to Race, which over the years has developed one of the most powerful motorcycles in its class.

The SX 125 has undergone numerous developments over time. KTM has often relied on innovations, such as the PDS system introduced in 1998 and discontinued in 2011, a shock absorber without linkage. Other milestones included the hydraulic clutch, which was available before the year 2000, taking a pioneering role in motocross, the extremely versatile WP air suspension, or finally the introduction of an injection system for 2-stroke engines.

Technical specifications KTM SX 125 2019 to 2022

Engine:

• Type: Liquid-cooled 2-stroke single-cylinder with power valve
• Displacement: 124.8 cc
• Bore x stroke: 54 x 54.5 mm
• Piston: Single-ring piston
• Lubrication: 1:40 mixture (2-stroke oil, JASO FD 100% synthetic standard)
• Ignition: DC CDI Kokusan
• Intake: Reed valve
• Fuel system: Mikuni TMX 38 carburetor
  • Main jet: 500
  • Pilot jet: 35
  • Needle: 6BFY43-71
• Clutch: Multi-disc clutch (Brembo hydraulic actuation)
• Starter: Kickstarter
• Spark plug: NGK BR9 ECMVX
• Transmission: 6-speed (Oil 15W50 JASO T903 MA2 standard)
• Final drive: 13/50 or 13/51 depending on model year

Maintenance: KTM recommends replacing the piston every 20 hours and changing the gear oil every 10 hours. Check your owner's manual to find all information regarding settings and maintenance.

Useful tip: A detailed table with all carburetor settings depending on conditions such as temperature, altitude, mud, or sand can be found in the owner's manual. This manual is available on the KTM website. It is very important to follow these guidelines to maintain the reliability and performance of your 125.

Chassis:

• Frame: Central double-cradle frame made of chrome-molybdenum steel / aluminum subframe
• Fork / travel: WP AER (Ø 48 mm air fork) / 310 mm, recommended oil: SAE 4
• Shock absorber / travel: WP DCC with linkage / 300 mm, recommended oil: SAE 2.5
• Front brake: 260 mm disc
• Rear brake: 220 mm disc
• Dry weight: 87.5 kg
• Seat height: 950 mm
• Front tire: 80/100-21
• Rear tire: 100/90-19
• Tank capacity: 7.5 l (Super Plus 98 recommended)

Maintenance: KTM recommends an oil change for the fork and shock absorber every 40 operating hours. Check your owner's manual to find all information regarding settings and maintenance.

KTM SX 125 in our online shop

In our online shop, we strive to offer you quality parts with fast delivery times and at the best price. For your 125 SX, you will find chain kits, fork seals, or oil for regular maintenance, as well as parts for customization: plastic kits, handlebars, grips, levers, and much more.