One of the team members picked up an old JLS RX4 and we wanted to upgrade it and see what we could do with it. The rifle is not very popular and it is hard to find solid info on it so we did a blog with pictures and a video to help get some info out there.


JLS RX4 airsoft gearbox

The RX4 was bought from another player and the upgrade parts were bought from AirsoftGI. Since this is more of a fun project and maybe a loaner gun we didn’t want to spend a lot on it and the store had the parts we needed. On the first look of the gearbox it reminds me of the old school G&G M14 from early 2000’s but not sure to compare side by side.


JLS RX4 gearbox review

These are parts that are going to be replaced. A new gearset would have cost more but getting a better airseal and stronger piston would be the best along with the torque motor since the stock motor was way too slow for any sort of gameplay.


Here is the video showing the break down of the gearbox and parts with some time lapse. The parts went in pretty easily. The off spec cylinder head had to be motivated into place but it still fit in the new cylinder. At the end of the video will be the assembly of the JLS RX4 from the gearbox.


JLS RX4 gearbox parts

The piston that we choice was the SHS piston with 3 steel teeth and for the price it will work great and last a long time. The second tooth was shaved down. Checking the AoE of the new piston and it was ok but no real concerns since the stock spring will still be used which is a M100 type or so. The piston head is the Super Shooter that is made out of aluminum and has the bearings which is a big upgrade from the old school TM spec and how the spring is locked into the nut of the piston head. Now since the stock spring has the hook at the end that would not work with the new piston head I just cut the section off and bent as needed to make sure it wont catch on parts as it compresses and it is good to go. The cylinder I used is the SHS M4 Cylinder and as I compare in the video there will be a little more air volume with this new part and that it is stainless steel it will have a better airseal with the new piston head.


JLS RX4 gearbox upgrade

The stock gears were covered in grease but shimmed great and there was no sign of rub marks or wear. I decided to just upgrade the Sector gear to another stock one I had in my bucket of parts. This new gear will have a larger delayer or nub for the tappet plate making it feed better on full auto. Since a new motor and lipo will be used in the gun this is needed and a cheap fix for any rifle.

SHS piston JLS RX4 upgrade

Here is the JLS RX4 gearbox some what put together and ready for a test fire. As you can now see the SHS piston and the shaved second tooth and the newer sector gear and how it will pull back the tappet plate for a little longer and allow better feeding of BBs. The tappet plate is like a V6 and V7 or P90 and M14 it seems and the spring must be wiggled into position from the inside of the gearbox. The SHS piston was able to slide freely on the piston rack in the gearbox which is a good sign. If it was too tight it would have stripped out.


JLS RX4 tappet plate

As you can see the tappet plate and nozzle it is unique and unsure if spare or upgrade parts are available.


JLS RX4 trigger contact

Close up shot of the trigger switch that is using the current day China plastic and metals which will hold up much longer than the first gen G&G M14 which had soft metal contacts. A mosfet could be added but that is out of the budget for this build.


JLS RX4 hop up

Very odd hop up unit and how it is like a TM M4 but it is not. It is a two piece unit with the lower part locked into the gearbox. The upper section can use a regular M4 type adjustment wheel and parts but the back end of the hop has a 2mm plastic spacer to separate from the gearbox.


Echo1 motor upgrade

To finish up the upgrade I will use the Short Echo1 Torque motor. The stock motor was very sluggish and barely wanted to work even with a lipo. Installing this new motor it cycled 3x faster and has a nice crisp shot with just about no lag which is great.


Team Black sheep Airsoft

Now that you have read and checked out what did to the rifle and made it better than new and did not spend too much it seems to be a great sounding rifle. We will have some future videos of it on the field so make sure you are subscribed to our YouTube Channel. Click on the picture above to watch the video on the JLS RX4.


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Written by Brian Holt