HK 4025 Series 4025-630 4025-740 4025-890 4025-1100 Kv (rpm/V) 630 740 890 1100 Max Power (W) 2520W 2450W 2380W 2200W Max Amp (15sec) 60A 70A 85A 100A Max Efficiency 85% 85% 85% 87% Io (No load A) 1.1A 1.33A 1.8A 2.4A Rm (Resistance) 0.024Ohm 0.017Ohm 0.013Ohm 0.008Ohm Shaft Diameter 5mm 5mm 5mm 5mm Gearbox N/A N/A N/A N/A Motor Diameter 48.9mm 48.9mm 48.9mm 48.9mm Motor Length 51.5mm 51.5mm 51.5mm 51.5mm Motor Weight 325g 325g 325g 325g Built in Fan Yes Yes Yes Yes Max Rpm 28,000 28,000 28,000 28,000 Poles 8 8 8 8 Case Outrunner Outrunner Outrunner Outrunner ESC Timing 20-25 deg 20-25 deg 20-25 deg 20-25 deg ESC Switching Freq. 8-16KHz 8-16KHz 8-16KHz 8-16KHz