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Hobbywing HW38020371 JUSTOCK COMBO JS4 G3S ESC + G2.1 13.5T MOTOR

Hobbywing HW38020371 JUSTOCK COMBO JS4 G3S ESC + G2.1 13.5T MOTOR

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Hobbywing HW38020371 JUSTOCK COMBO JS4 G3S ESC + G2.1 13.5T MOTOR

Introducing the Hobbywing Justock Combo ‘JS2’ with XR10 G3S speed control, paired with the Hobbywing  G2.1 13.5T fixed timing brushless motor.

The XR10 Justock G3S has precise control and powerful performance.  It is suitable for 1/10th on-road and off-road zero-timing (blinky) competitions.

This speed control is not BRCA legal for 2024 Nationals in the control 17.5T or FWD class.  Control products for that class are HW30112003, HW38020321, HW30408011

Speed Control Features.

Fan intelligent start and stop function
When the ESC temperature is low, the fan does not activate, when the ESC temperature reaches the preset value, the fan automatically turns on.
The intelligent start and stop function of the fan not only reduces noise, saves power, but also ensures that the ESC works in a good temperature range.

Freewheeling Feature
With the freewheeling function turned-on, the ESC temperature is lower, the vehicle decelerates faster when the throttle input is off, and it has better controllability around the corners.

Built-in polarity protection
One danger that all electrical systems face is a reversed polarity from the power source. This can be caused by a short circuit, or usually, accidentally reversing the terminals.

Multi RPM limit, select as needed
Supports 79RPM Limits
(10000-88000RPM)RPM limit value selection. It can be programmed through the LCD programming box or OTA module. It is simple and convenient to meet the RPM limit requirements of various competitions in the world.

Built-in capacitor module, optimized layout
The built-in capacitor module eliminates the need for external capacitors and unwanted space.

Built in BEC
The ESC has a built-in BEC which can support a maximum output current of up to 8A. The output voltage at either 6V or 7.4V. This will ensure constant power supplied to today’s high-torque servos in the market.

Built-in data logging function
The ESC has a built-in data recording function making it easy to obtain the operating status.
The data includes;

Minimum voltage
Maximum ESC temperature
Maximum current
Maximum motor temperature
Maximum RPM

Wireless connection for data recording and analysis
After the ESC is connected to the OTA Bluetooth module, connect to the ESC through the HW Link mobile app and turn on the real-time data recording function. You can view data such as throttle, voltage, current, temperature, speed, etc. in real time. In addition, OTA can record the above data using HW Link. Easy to implement data analysis functions. Note: Due to the Bluetooth transmission distance, the effective distance is about 5m!

Parameters optimized
It is tailored and are more in line with competition needs.


Scale – 1/10th
Brushed/Brushless – BL
Sensored/Sensorless – SD
Waterproof – No


Cont./Peak Current – 60A/380A
Input Voltage – 2S LiPo
BEC Output – 6V/7.4V @4A

Wires & Connectors

Input Wires – Black-14AWG-200mm*1 Red-14AWG-200mm*1
Output Wires – Black-14AWG-200mm*1 Black-14AWG-200mm*1 Black-14AWG-200mm*1
Input Connectors – No
Output Connectors – No


Size – 25x25x10mm
Output Wires – 5-7.4V
Input Connectors – Powered by BEC

Data Recording

Extreme Value – Not Supported
Real-Time Date – Not Supported
Historical data (Graph) – Not Supported

ESC Programing via

SET Button on ESC – Not Supported
LED Program Box – Not Supported
LCD Program Box – Supported
WiFi Module – Supported
OTA Programmer – Supported
Programming Port – Separate


Firmware Upgrade – Supported

Size & Weight

Size – 40.9×33.9×32.1mm
Weight – 75.4g(w/Wires)


Applications – SL BL Motors / SD BL Motors
Vehicles – 1/10th,1/12th On-road and Off-road club competition and normal training
KV Rating/T Count – ≥10.5T 3650 Motor


Motor Features

– The use of a heat-resistant magnet attached aluminum case and double insulated windings, high precision bearings, and rotor with a strong structure guarantees outstanding performance and super durability.
– The built-in Hall sensor non-adjustable end bell combined with a high precision and balanced rotor guarantees the user a smooth and linear power on demand.
– The silicon O-ring seal fitted between the end bell and stator helps to conduct inner heat to the motor case and prevent dust from entering the HALL sensor.
– The detachable structure design for daily cleaning and maintenance can effectively prolong the service life of this Justock motor and improve its operating efficiency.
– This motor is perfectly matched with the XR10-Justock ESC for all zero timing spec racing and also compatible with other Hobbywing Electronic Speed Controllers including other brands.
– This Justock motor is applicable to various 1/10th, 1/12th on-road & off-road vehicles. It can be an ideal choice for Stock or Sport class races but can also be a nice choice for newbies for practice.
– The motor design is in compliance with IFMAR, and ROAR specifications.

Additional information

Weight 501 g






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