KP30145 RSx4S Power H.C.



#Torque: 31.6Kg-cm Speed: 0.11sec/60deg(@7.4V)
#Torque: 26.3Kg-cm Speed: 0.13sec/60deg(@6.0V)

Reference Spec
#Torque: 33.0Kg-cm Speed: 0.09sec/60deg(@8.4V)

#Dimensions: 40.4×37.5×20mm (Standard size)
#Weight: 75.2g
#Servo Lead: 230mm
#Operating voltage: 6.0~7.4V (Lipo, Life, Ni-MH)
#Core-less motor
#Reinforced stainless steel final gear
#Hard alumite aluminum gear
#Dual ball bearings
#Hard servo gear shaft
#Aluminum top case
#Aluminum heat sink middle case
#Black cable
#Gold plated connector
#Serial Compatible
#HCS Compatible

#Recommend category
 1/8 Off road, 1/8 On road, 1/8GT. Crawler

Made in Japan.

Last items in stock


RSx standard size series evolves to serial communication​

The "RSx" standard series, which has been loved by many users for many years and has been active in races around the world, has evolved to be serial compatible while maintaining its basic performance. By combining this with the EX-NEXT advanced mode, the RSx series can provide even better response performance than before. In addition, by using the telemetry function of EX-NEXT, it is now possible to change the ICS parameters of the servo from the radio. Since the EX-NEXT supports conventional HCS and standard communication specifications, it can be used not only with the serial-compatible KR-420XT but also with a wide variety of receivers.

Compared to the "Grasper STD" with brushless motor, the "RSx4S" with coreless motor has a milder operation feeling. Use the RSx4S according to your preference of machine, course, and driving feel.




Reinforced stainless steel final gear

The RSx4S(Standard size) uses stainless steel for the final gears to strengthen the durability of the gears. In addition, the height of the serrations on the final gear has been adjusted slightly higher to allow the use of multiple servo horns. The number of teeth and diameter of the serrations are unchanged.


*The stainless steel material has been treated with nitriding to strengthen its durability. The finish is different from the anodized aluminum color used in the past.



Implemented a "4S" system that supports serial

The "4S" servo supports serial. By supporting serial, there are the following merits.


(1) Ultra-high-speed communication dramatically improves response.

The PWM method is the mainstream control method for RC servos. In the PWM method, the angle is specified by the width of the signal transmitted from the receiver. On the other hand, in serial communication, the servo angle can be specified numerically. In serial communication, the communication interval can be significantly shortened compared to the PWM method, and the interval from command to operation is greatly reduced. By combining with EX-NEXT's XT mode, we have achieved an unprecedented ultra-fast response as if you were just touching the machine.   

(2) Servo parameters can be changed from the radio at hand

 The next-generation radio "EX-NEXT" is equipped with a telemetry (two-way communication) function."REAL TIME ICS" can be used by connecting the serial compatible servo "4S" to the B / S port mounted from the new receiver KR-420XT. Servo parameters can be set arbitrarily from the radio without having to collect the machine at hand. It's easier than ever to create a more flexible and in-depth settings without compromise.

When using serial, connect to the B / S port of the KR-420XT in XT mode of EX-NEXT.


"Serial Branch adapter" ideal for serial wiring

The KR-420XT receiver is equipped with a single B/S port (serial port) for connecting serial servos, and for GP cars, etc., where two servos are used, the optional "Serial Branch adapter" is recommended for splitting the port.

 Product page: Serial Branch adapter


This product is more compact than the conventional product by using a smaller base for the branching point, making it easier to store in the limited space of a GP car.


If you want to use two serial servos at the same time, you need to change the ID number of each servo. the ID number can be easily changed by connecting to [LCD Expansion Unit 2] of EX-NEXT. for how to change the ID number, refer to "LCD Expansion Unit For details on how to change the ID number, please refer to "LCD Expansion Unit 2 EXP-201 Startup Guide".


Electrical Switch3

The Serial servos and the Electrical Switch 3 can be used together.
When the B/S port of the KR-420XT(receiver) is occupied by the serial servos, connect the Electrical switch 3 to one of the available 1CH~4CH.





Added "Frequency" as a new parameter

RSx4S can change various characteristics to your liking by ICS, but "Frequency (FREQUENCY)" has been newly added from 4S. "Frequency" is a function to change the frequency of the motor built into the servo. By changing the frequency, the servo Activity changes. Direct feeling improves by lowering the frequency. The servo operation becomes active and the machine will bend sharply. The higher the frequency, the smoother the servo will move. The activity will be calm and you will be able to bend smoothly. Please select your favorite characteristics while changing the settings.



Compatible with conventional systems (PWM)

It can also be used in HCS, which has been well received, and in normal mode, which can be used for a wide range of models.



The communication processing time between the receiver and the servo is compressed to 1/4, and it can be used with a direct operation feeling.


[Normal mode]

System used for servos and ESC’s that has been adopted for many years. It can be used with many receivers.



Serial / HCS / normal mode switching method.

The servo automatically switches depending on the port connected to the receiver and the mode setting. No additional options are required for mode setting. If you want to use it serially, connect it to the B / S port of KR-420XT. Also, when using with HCS, it can be used simply by connecting to channels 1 to 4 set in HCS. The same applies to normal mode. Of course, it can also be used with the KR-418FH and other receivers that have been released so far. * Only KR-420XT can be used for serial mode. For conventional receivers, use HCS or normal mode.


Tight black and silver color aluminum top case

An aluminum case is used for the top case that supports the [holding power] that does not shake. By further cutting after alumite treatment, a sharp form with an edge is created (chamfering). Furthermore, by cutting the inner thickness to the utmost limit, the product is lightweight while maintaining sufficient strength.




Reduced case size for easy installation in chassis

By reducing the size of the servo case in the longitudinal direction from 41.0mm to 40.4mm, it is now easier to mount servos in a variety of the GP car.




Easy-to-manage black servo wire

Commitment extends to servo leads. The black cable, which looks tight, has the optimum softness for handling while ensuring the required current capacity. The length of the cable has been changed from 200mm to 250mm.
This has made it possible to install the product in many car models without difficulty.




5 patterns of presets available

Five presets are installed in the model memory of the RSx4S. You can use them properly according to the machine and road surface. Please use the servo model selector to switch the servo function that can handle various situations with one servo.


Model 1: Power saving high
Model 2: Power saving low  (Factory setting)
Model 3: Balance
Model 4: Performance
Model 5: High performance

*The factory default setting is "Model 1".


Please use "Servo Model Selector for 4S" to switch models.

* The conventional servo model selector (No.61029) cannot be used.



・Factory Default setting data



Model Setting Sheet

The RSx4S allows you to change the parameters of each model with EX-NEXT. Please download and use the following sheet as a reference for your settings.




LCD Xpansion unit 2 Parameters can be changed from EXP-201


You can connect a servo to the Xpansion and set the characteristics to your liking by operating the Xpansion buttons. Compatible servos are all models equipped with ICS. Of course, it also supports RSx4S.

* A separate power supply (6 to 7.4V) and "twin extension wire" or "Serial Branch adapter" are required.

* This product does not support parameter changes by the servo manager connected to a PC.



Please be careful

There may be slight vibration under no load, but this is not a malfunction. This servo sets the parameters to optimize the driving condition. Therefore, when viewed with the servo alone, the output shaft may generate slight vibrations or drive noise, but this is not an abnormality and does not interfere with operation.

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Specific References