KTM 125 SX
Although KTM has been building motocross bikes for many years, the lineup only received the “SX” designation in 1993. The name directly references the legendary American Supercross series (SX), where winning requires an extremely high-performance bike, both in terms of chassis and engine. These qualities perfectly reflect KTM’s slogan, “Ready to Race,” and over the years, the SX has become one of the most powerful bikes in its class.
The SX 125 has evolved significantly over time. KTM has always been committed to innovation. Notable examples include the introduction of the PDS rear suspension without linkage (launched in 1998 and discontinued in 2011), the hydraulic clutch, a true gamechanger in motocross before 2000, the highly versatile WP air fork, and even the introduction of fuel injection for 2-stroke engines.
Technical data KTM 125 SX 2016-2018
Engine:
- Type: Single-cylinder 2-stroke engine, liquid-cooled, with exhaust valve
- Displacement: 124.8 cc
- Bore x stroke: 54 x 54.5 mm
- Piston: 1-ring
- Lubrication: Mixture 1:40 (2-stroke 100% synthetic oil, JASO FD standard)
- Ignition: DC CDI Kokusan
- Intake: Reed valve
- Carburetor 2016: Keihin PWK 38S carburetor
- Main jet: 182
- Idle jet: 50
- Needle: N1EF
- Carburetor 2017-2018: Mikuni TMX 38 carburetor
- Main jet: 480
- Idle jet: 45
- Needle: 6BFY43-74
- Clutch: Multi-disc clutch (hydraulic Brembo)
- Starter: Kick starter
- Spark plug: NGK BR9 ECMVX
- Gearbox: 6-speed gearbox (oil 15W50 standard JASO T903 MA2)
- Gear ratio: 13/50
Maintenance: KTM recommends replacing the piston every 10 operating hours and changing the gearbox oil every 10 hours. All adjustment and maintenance information can be found in the owner’s manual.
Tip: The manual includes a detailed carburetor tuning table for different riding conditions (temperature, altitude, mud, or sand). The manual is available on KTM’s website. Following these instructions is essential to preserve the reliability and performance of your 125 SX.
Chassis:
- Chassis: Chrome-molybdenum steel tube / aluminum rear frame
- Fork / suspension travel: WP AER (air-sprung fork Ø 48 mm) / 300 mm → recommended oil: SAE 4
- Shock absorber / suspension travel: WP 4CS with linkage / 300 mm → recommended oil: SAE 2.5
- Front brake: 260mm brake disk
- Rear brake: 220mm brake disk
- Declared dry weight: 87.8 kg
- Seat height: 960 mm
- Front tire: 80/100-21
- Rear tire: 100/90-19
- Fuel tank: 7.5 liters (98 unleaded petrol recommended)
Maintenance: KTM recommends changing the fork and shock oil every 40 operating hours. All adjustment and maintenance information can be found in the owner's manual.
KTM 125 SX in our online store
In our store, we offer you high-quality parts quickly and at fair prices. For your KTM SX 125 you will find chain sets, fork seals and oil for regular maintenance as well as parts for customization: plastic kits, handlebars, grips, levers, etc.
