Air Seal Nozzle Not Sealing Properly
 

What can I do to the air seal nozzle to fix this issue?

I know that it's my air seal nozzle that's not sealing the air properly because I did a compression test without the nozzle and the piston head and cylinder head was sealing in air very well.

It might be an issue with your hopup sleeve, then. Try testing some other sleeve brands.

By the way, your signature picture is currently over forum limit. Please reduce it accordingly.

what brand is it? Get the Prometheus brand.

Oh, and by the way, it almost never seals 100% perfectly with the air seal nozzle off the base of the cylinder head. So it's not that rare to have an airseal issue there.

But I really think it's the air seal nozzle. My gun is all taken apart and I have the gearbox open. So I doubt that it's the hop-up rubber sleeve, well as for now.

Yeah it's a Prometheus Air Seal Nozzle.

So you're saying that with my finger on the air seal nozzle while doing a compression test, I shouldn't be getting that good of air seal or not as good as if I just have my finger over the cylinder head without the nozzle?

If your nozzle has a tiny little o-ring in it...you can pick out the o-ring with a very fine flat screwdriver...lube it up and put it back in...(or swap the o-ring with a thicker one if you can find one that fits)

If it's a small slow leak...I'd leave it. If it was a bad leak and if I had tried several nozzles and none of them would seal, I'd swap the cylinder head.

it's almost never perfect, doesn't really matter whether you got a airseal nozzle with the O-ring or not. If it was such a tight airseal, then the airnozzle wouldn't be able to move.

Try putting it back in the gun first, and chrony all the shots. If it has a good airseal overall, the FPS deviation over 10 shots should be about 5FPS.

could it be the junction nozzle/hop-up?

Maybe your piston head o-ring?..

could be, but very unlikely.

What cylinder head are you using?

So how much loss are we talking about? Because when I'm trying to do a compression test, I can push the piston up the cylinder fairly easily with my finger over the air seal nozzle.

I'm using an ARS MASK Aluminum Cylinder Head with a sorbo.

The compression on my cylinders is always incredibly, with all my strength I can barely move the cylinder inside the piston, usually wont move past half way regardless of how much grunting and heaving I do.

I had problems with a Prometheus airseal nozzle on a Guarder cylinder head once, no airseal at all. Prometheus airseal nozzles have always worked flawlessly for me on Modify cylinder heads. I also always use double o-ring cylinder heads and so far with them (Guarder or Modify) I have never had any air leak around there.

One thing I always try to do is keep all the airseal components the same brand. So Piston head, cylinder, cylinder head, and nozzle. I usually go for Modify since they are fairly cheap and have amazing quality and as I said I have also had no problems with Prometheus nozzles on Modify cylinder heads. One mistake that a lot of people make with ventilated piston heads is to just put some thin lube around the o-ring and put it in. I have tried this and the airseal is never as good as when I lube it really well with thick lube. I use white lithium grease from the automotive department of Canadian Tire, comes in a tube for I think $4 or something, enough to last me (a regular gun doc) 6 months. I take off the o-ring, fill the piston head with grease, then put the o-ring back on, usually pressing lube out of the vent holes like spaghetti. Using this lube method I have never had a ventilated piston head with a good o-ring cause an fps reduction like some people have had.

If you put your thumb over the cylinder head and press the piston, and the seal is good, but then you put on the nozzle and repeat and the seal is bad, then yes its the airseal nozzle.

No, because I get a perfect air seal without the air seal nozzle and with my finger over the cylinder head.

How fast are you moving the piston? If you have a ported piston head, it takes a little speed to get the piston o-ring to expand and create a seal internally. If you're pushing it slowly, it'll look like an air leak because the o-ring isn't expanding.

EDIT: Nevermind, your last reply negates my answer.

Just tried that, I lubed up the o-ring with some silicone. But I'm still not getting a good air seal.

I'll see if Home Depot has any o-rings that are the same size but a little thicker.