Scorpion HKIV-4025-520 Brushless Motor, Kv=520

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Scorpion HKIV-4025-520 Brushless Helicopter Motor

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Back in 2010, when the new Scorpion HKIII-40mm Series Motors were released, a lot of feedback from both World Champions and Sport Pilots in all facets of the hobby was received. Pilots from around the world agreed that the HKIII-4025 series motors had established themselves as the Gold Standard of R/C model helicopter power, and had become the most popular motor used in 550 ~ 600 class helicopters.

Now, we are pleased to announce the release of the fourth generation, HKIV-4025 Series Motors. Using the same motor design and materials from the HKII-45 series motors, including the single strand winding technique, this newest version has better efficiency and power conversion than the earlier HKIII-40mm series. With an entirely new EM field design, the compatibility with various speed controllers available on the market has also improved. This new design motor will deliver even more power to your helicopter, with increased efficiency, making it the best helicopter motor available for your model!

The Scorpion HKIV Series Brushless Motors are built from the best materials available, and are designed to provide both quality and performance at an affordable price. Scorpion starts with high quality aluminum alloy parts that are produced on the latest CNC milling machines. These parts are then gold and black Electro-Coated to provide a beautiful, long-lasting finish. The stators are made with 0.2mm laminations to give maximum efficiency, and minimum Eddy current losses. The stators are all hand-wound to insure the highest copper fill rate with wire that is rated at 180 degrees C (356 F), and high voltage tested to insure that no shorts are present. The high temperature magnets used in Scorpion Motors are designed to give top performance in the most demanding applications.

All Scorpion HKIV-4025 series motors come with the new High-Current, locking style, 4mm male Bullet style connectors already attached, and include a hardware package that contains four socket head M4 x 0.7mm mounting screws, four socket head M3 x 0.5mm mounting screws, plus three 4mm female bullet connectors for your speed controller with molded plastic covers. For maximum strength, the Scorpion HKIV-4025 series motors feature an 8mm motor shaft that is ground down to a 6mm diameter at the output end to fit standard size pinion gears. Since the HKIV Series motors are primarily designed for Helicopter use, they do not include a prop adapter. If you intend on running a prop on this motor, you will need to purchase a prop adapter for a 6mm shaft.

Scorpion Motors are built to last, and are backed with a 2-Year warranty against defects in materials or workmanship. However, due to the high RPM of these motors, and the fact that we cannot control the installation and setup, the bearings are not covered by the 2-Year warranty, nor is any subsequent damage caused to the motor by a bearing failure. Bearings are a normal wear item, and as such, need to be maintained and changed periodically. For maximum life, make sure that a sufficient gap is left between the pinion and main gear during motor installation to avoid binding, and put a small drop of oil on each bearing every 5-6 flights. It is the responsibility of the pilot to ensure that the bearings are maintained properly.


Scorpion HKIV-4025-520 Motor Specifications
Stator Diameter
40.0 mm (1.575 in)
Stator Thickness
25 mm (0.984 in)
Number of Stator Slots
Number of Magnet Poles
Motor Wind
6+7 Turn Delta
Motor Wire
1-Strand 1.20mm
Motor Kv Value
520 RPM per Volt
No Load Current (Io)
1.81 Amps @ 10 Volts
Motor Resistance (Rm) per Phase
0.022 Ohms
Maximum Continuous Current
65 Amps
Max Continuous Power (12-cell Li-Po)
2886 Watts
Motor Weight
347 grams (12.24 oz.)
Outside Diameter
49.50 mm (1.95 in.)
Shaft Diameter
5.98 mm (0.235 in.)
Shaft Length, From Mounting Face
30.6 mm (1.20 in.)
Motor Body Length
54.0 mm (2.13 in.)
Overall Shaft Length
84.6 mm (3.33 in.)
Max LiPo Cell
Peak Current
90 Amps (5 seconds)
Peak Continuous Power
3996 Watts (5 seconds)
Motor Timing
Drive Frequency

Weight including packaging


View Scorpion HKIII-4025-520KV Full Dimension
Scorpion HKIV-4025-520 Motor

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