Firma 3900Kv 4-pole Brushless Motor

Item No. 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


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


Motor Type
Maximum Continuous Current
Shaft Diameter
0.2" (5 mm)
1/10 Scale Surface
Connector Type
4mm Bullet
Product Length
2.35" (60 mm)
Outer Diameter
1.4" (36 mm)
Input Voltage
RPM/Volt (Kv)