Quick Oil change method for pneumatic spearguns

  • The usual procedure for changing the oil in pneumatic spearguns is to let all the air out, unscrew the muzzle and then pull the piston out of the inner barrel. After that you can tip the gun upside down and pour the oil out of the inner barrel. Guns with a power regulator block tend to trap oil in the front tank, so to remove everything you can twist the nosecone off and then pour the oil out of the front tank at the same time as you empty out the inner barrel.

    This alternative method uses the air pressure in the gun to blow all the oil out of the rear inlet valve and to do that without making a big mess you need a gadget like that shown in the diagram below. This device was developed for the "Taimen" which has a thick plastic valve stem, so you don't want to push that stem with anything sharp, instead use just a smooth ended rod that fits neatly in the inlet valve port. The gun is held with the muzzle pointed upwards and vertical and then pushed firmly onto the vertical rod which cracks open the rear inlet valve and the oil sitting in an accumulation in the rear of the gun is all blown out by the air pressure acting above it. In a big gush of air escaping all the oil is blown into a receptacle such as an old ice-cream container for your subsequent inspection to see if there is any water or foreign materials contaminating the oil that would necessitate gun dismantling to investigate the source of any problems.

    gun cleaning oil removal R.jpg

    If the oil looks good then you discard it, put fresh oil in a glass bottle or jar and suck it up with the hand pump and attach the gun to the pump, the gun still being held muzzle up and then invert the assembly and with a slow firm push press down on the pump handle and send the oil in the pump into the gun. Repeat as necessary to ensure the correct amount of oil is replaced in the gun and that is all there is to it. Make sure that the gun is set to full power when you do this as compressed air pressure can act on all the oil sitting in the rear end of the gun.

    Note that a slow push is required as you don’t want the oil being forced in too rapidly which may blow the inlet valve “O” ring out of position, an unlikely outcome, but better to be safe than sorry.

    Periodically the piston needs to come out to check for any wear and scratches on the piston and its seals, but this is unlikely unless you dive in very dirty and gritty water or spear in the shore break where schools of fish often run through feeding on material being churned up off the sandy bottom. I have bumped off quite large flathead doing this when I saw them zipping around my fins while standing on the bottom, so swam out and then turned back to open fire on the fish which are very hard to hit, so more ass than class in hitting one.

  • It occurs to me that the gadget shown in grey is something that could be 3D printed, or turned up out of wood with a metal rod for the probe that pushes on the valve stem or metal ball as the case may be.

  • Thanks for the instructions Pete. Is the grey gadget basically a pin/rod of the correct diameter?

    Does this method work with pneumatic spearguns from other brands, and only requires different diameter pins?

    Dan the gadget is basically a stand with a rod than can be changed over for different speargun models, however most using ball inlet valves are exactly the same size, so in most cases the one rod would be universal. Guns like the "Taimen" using a valve stem are the few exceptions today, in fact ball inlet valves have been around for decades and go back to the early seventies. The "Taimen" is unusual as it has no valve spring, the valve stem being a sort of jiggle pin, the reason being that the compact design has no room for a biasing spring. The valve stem was originally metal, but is now plastic to prevent galvanic reaction with the alloy rear housing. This is because the tail cap always floods and water can reach the valve stem, the tail cap being a plastic bung which just pushes in and is held in place by an upper transverse screw in the rear of the clamshell plastic handle. Being plastic the valve stem is fatter than usual and needs a broader flat ended pin that will not bust the valve stem, hence pointy metal objects are forbidden if you need to let the air out of the "Taimen" gun.

    This method will work for every pneumatic speargun that has a rear inlet valve, the only exception would be guns that don't have a hand pump connection and use the inner barrel as a hand pump, such as Zekinka guns. However even some Zelinksy system guns today have a rear inlet valve, such as the Pelengas "Z-linka" shown here.

    Zelinsky system guns, often referred to as "Zelinkas", are uncommon in the West, but are highly sought after in Russia, Ukraine and the former Soviet Republics.

    This one is constructed almost entirely from titanium with a stainless steel inner barrel and is a very long lived underwater weapon in terms of its service life.

    Edited 5 times, last by popgun pete: added a comma ().

  • Note that upside down positioning of the gun is vital to using the air pressure as a driver to force all the oil sitting below it to be ejected, the oil comes out first followed by the compressed air. As with muzzle removal to do the same job it is best to stand the gun with muzzle up and butt down in a room corner for say 20 minutes to allow the oil to accumulate in the rear end of the gun with the power regulator set to full power.

  • Pelengas spearguns have a molded inlet valve cap with a wide screwdriver slot in the rear which is curved rather than straight cut across to form a slot. Unfortunately a screwdriver blade will twist out and rip up the plastic, so you really need a coin to undo it. The molded threads are very tight at first and even gripping a coin can be problematic. However in a 2 dollar shop I found this version of a mini vice-grip which with a coin makes the perfect tool for undoing this rear cap as you can press while twisting which removes any risk of tearing the cap, something very easy to do otherwise as it is hollow like a thimble and is not solid.

  • One thing that I forget to mention is that with power regulated pneumatic guns you need to set them to "full power" and have the gun slightly tilted so that the oil runs down through the now open transfer port before you press on the inlet valve. The tilting places the transfer port to act as a drain hole for the front tank by being the lowest point, otherwise oil sitting inside there will not be blown out. That gun positioning then allows all the oil in the gun to run down into the rear end of the inner barrel which you are intending the air pressure release to blow all the oil out of via the back end of the gun.

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