Ninja HP Regulator Overhaul

We have a tendency to take our HP air systems for granted. But even they need a bit of love every now and then. The Ninja Regulator shown here is an older one that I’m salvaging from a 4500 air system but it’s very similar to the current model. I have a couple of these that I’m rebuilding as spares.

First of all HP Air Systems need to be treated with respect. They can kill or injure you if you don’t know what you are doing. If in doubt leave it to a professional.

To disassemble you first need to empty the air system. This can be done using a spare ASA or removing an o-ring and using one of your markers. Check that the cylinder is completely empty by pushing in the pin valve. Now you can remove the bonnet locking screws and unscrew the bonnet. Next you can remove the main spring and any shims present. Finally, wiggle the regulator piston until it and the pin valve come out of the bonnet. Don’t use pliers as they may damage the piston.

Now give everything a good clean with q-tips and a lint free cloth. Check the piston seat seal for wear and that the piston o-rings are not worn or perished. Replacement pistons are fairly inexpensive so if there is any sign of damage to either the seat seal or the o-rings it’s easier to replace the whole unit (btw the o-rings are 008-90U & 012-90U).

Now reassemble the regulator in reverse order. The piston o-rings need to be lubricated first with a silicone grease. Never use oil on high pressure air systems. There is a serious explosion risk if you do. It is recommended that the regulator seat and the pin valve o-ring be left dry. Lubricant on these can allow debris to stick and cause leaks. Carefully insert the small spring and pin valve into the piston and slide the whole assembly into the bonnet making sure it is all the way in. Now place the shims followed by the main spring into the regulator body. You can now screw the two halves together. When properly assembled the bonnet should sit flush with the top of the regulator body. Finally, refit the locking screws. Job done!

The first sign of a regulator fault is a blown 1.8k burst disc. This burst disc sits on the output side of the regulator and is designed to protect your paintball marker from full bottle pressure. So if your 1.8k burst disc blows it’s a sure sign that your regulator needs maintenance.

The other burst disc sits on the cylinder side of the regulator and is there to prevent overfilling. 4500 psi systems will have a 7.5k burst disc fitted whereas a 3000 psi system will have a 5k burst disc. When replacing a burst disc make sure you use the correct replacement. Burst discs need to be torqued to between 55 and 95 inch-pounds to seal properly (do not over tighten).

You will also have noticed that there are two red shims sitting under the main spring. These are used to adjust the output pressure of the regulator. From the factory the output pressure is set to between 800 – 900 psi. Removing one shim lowers the output pressure to around 650 psi. Removing both lowers it to around 500 psi.

If you have a Ninja Pro series regulator the main difference is the use of a Belleville spring stack instead of a coil spring. The basic operation of the regulator is the same.

Manuals for all Ninja products can be found here: