Firma 3900Kv 4-Pole Brushless Motor

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Spektrum SMART #SPMXSM3300
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  • (1) Spektrum Firma 3660-3900kv Sensorless 1/10 Brushless Motor with 4mm Gold Plated Bullet Connectors
  • (1) Product Manual
  • Electronic Speed Control such as the Firma 130 Smart ESC
Firma 3900Kv 4-Pole Brushless Motor


Great choice for 1/10 Scale 4WD models looking for a high RPM motor upgrade running up to 3S * (12.6v) power. Low cog 4-pole rotor design, CNC machined aluminum housing, insulated high purity copper windings, high-quality alloy steel 5mm output shaft, and high-precision bearings for high durability and smooth rotation. Preinstalled with 4mm gold plated bullet connectors for easy installation. Perfectly matched for the Firma 130 Smart ESC.

*Will work with the 85A Firma ESC, but only for 2S power.


  • Perfect upgrade for brushed 540- and 550-size brushed motors with the same diameter and mounting pattern (vehicle must accept pinions with a 5mm bore)
  • High-quality 4-pole sintered rotors
  • Includes 4mm gold plated bullet connectors
  • Precision ball bearings and hardened steel 5mm shaft
  • SafeD-5 Pinion compatible

Product Specifications

Connector Type
4mm Bullet
Motor Class
1/10 Scale
Product Length
2.35" (60 mm)
Integrated ESC
Constant Wattage
Maximum Continuous Current
Motor Type
Input Voltage
Kv Rating
3000Kv or more
Motor Output Lead
RPM/Volt (Kv)
Sensor Type
Outer Diameter
1.4" (36 mm)
1/10 Scale Surface
Shaft Diameter
0.2" (5 mm)