Engineered as an engineering milestone in competition servo technology, the KST X20-4208 is the industry's first standard-size digital servo to combine an ultra-responsive 4-pole brushless DC motor, proprietary High Life Span (HLS) hardened steel gears, and a revolutionary 6-ball-bearing (6BB) drive architecture. Delivering a massive 46 kgf.cm of stall torque, a blisteringly quick 0.07s/60° transit speed at 8.4V, wear-free contactless magnetic sensing, and IP65 splash-proof sealing, the X20-4208 provides unbreakable steering authority and surgical centering accuracy for 1:7 and 1:8 scale competition buggies, truggies, on-road GT racers, giant-scale aerobatic planes, and turbine jets.

Key Features

• Industry-First 6 Ball Bearing Architecture (6BB): Six precision ball bearings provide total radial and axial support across every gear shaft, eliminating geartrain flex, reducing rotational friction, and guaranteeing zero gear slop even under violent track impacts.
• High-Torque 4-Pole Brushless Motor: Advanced 4-pole stator design produces significantly higher electromagnetic torque density, instantaneous throttle-to-steering response, and superior thermal efficiency during grueling endurance mains.
• Wear-Free Contactless Magnetic Sensor: Hall-effect position sensor completely eliminates physical potentiometer wiper wear, resistive track degradation, and vibration noise — delivering permanent, millimeter-precise centering repeatability.
• Proprietary HLS Hardened Steel Geartrain: High Life Span (HLS) alloy treatment withstands extreme shock loads, high-traction curb strikes, and harsh off-road landings without stripping teeth.
• Formidable 46 kgf.cm Torque & 0.07s Speed: Delivers unyielding holding force and instantaneous wheel positioning under extreme centrifugal cornering loads.
• IP65 Splash-Proof Construction: Sealed CNC aluminum housing protects delicate internal electronics and geartrain from wet tracks, mud spray, and abrasive track dust.
• Expansive 200° Default Travel: Wide ±100° (200° total) factory travel angle provides exceptional throw for crawlers, large control surfaces, and robotic actuators (endpoints programmable).
• Programmable & Soft Start: Customize travel endpoints, direction, and soft-start ramp protection via KST USB Link/programming box to protect linkages on power-up.

*Note: Never connect or disconnect the servo to/from a live, powered electrical system.

Technical Specifications

• Model: X20-4208 Heavy-Duty Brushless Servo
• Application: 1:7 & 1:8 Scale On-Road / Off-Road RC Cars (Buggy, Truggy), Aerobatic Airplanes, Turbine Jets
• Rated Voltage: DC 7.4V
• Voltage Range: DC 6.0V – 8.4V (2S LiPo Direct Drive)
• Motor Type: 4-Pole Brushless DC Motor
• Gear Set Material: Hardened Steel / HLS (High Life Span)
• Case Material: CNC Aluminum Alloy
• Bearings: 6 Ball Bearings (6BB)
• Position Sensor: Contactless Magnetic (Hall Effect) Sensor
• Water Resistance: IP65 Splash-Proof
• Working Frequency: 1520μs / 333Hz
• Default Travel Angle: ±100° (200° Total, Programmable)
• Operating Temperature: -20°C to +65°C
• Soft Start / Programmability: Yes (Programmable)
• Dimensions: 40.0 × 20.0 × 40.0 mm (±0.2mm)
• Weight: 80g (±10%)

Performance Ratings

• Stall Torque:
  • 38 kgf.cm @ 6.0V
  • 42 kgf.cm @ 7.4V
  • 46 kgf.cm @ 8.4V
• Operating Speed (No-Load):
  • 0.10 sec/60° @ 6.0V
  • 0.08 sec/60° @ 7.4V
  • 0.07 sec/60° @ 8.4V
• Stall Current:
  • 8.80A @ 6.0V
  • 10.80A @ 7.4V
  • 12.30A @ 8.4V

Dimensions & Sizing

Documentation

• X20-4208 Technical Specification