Tuning Hatsan flashpup .22 leak still a mystery

[daddyrabbit]

I posted here about a year ago with a leak problem I was having with my hatsan flashpup and I have yet to figure it out. The leak is definitely in the fill port check valve. I've cleaned and changed the check valve o ring about ten times with the same result each time ending with the check valve leaking. 

Here's the part that baffles me. You can change the o ring on the check valve and fill the gun to 200 bar and it will not leak until you shoot two or three magazines through it then all at once you'll hear air hiss out of the fill port and it'll be empty in two minutes. The last time I changed the o ring on the fill port check valve I filled the gun to 200 bar and put it away in my gun cabinet and did not touch it for ten months and when I pulled it out after ten months it was still holding the full 200 bar. I took it outside to shoot it and half way through the third magazine it released the dreaded hiss of air from the fill port as it has so many times before.

I've cleaned it properly including the tank as well as used hatsan o rings with silicone grease etc. The o rings always look perfect when I inspect them. There's not much in this world I can't fix sooner or later but I've hit a brick wall on this one. Do any of you have any thoughts on this pickle.

 

[Raden1942]

I think there's a good chance that you have some debris inside the check valve or that the check valve has some kind of deformation. When it has a full air tank the pressure likely overcomes the problem and as soon as it gets below a certain level it just dumps out. I believe that if you install a new check valve it will solve your problem. I had the same issue with my Benjamin marauder. 

 

[daddyrabbit]

I think there's a good chance that you have some debris inside the check valve or that the check valve has some kind of deformation. When it has a full air tank the pressure likely overcomes the problem and as soon as it gets below a certain level it just dumps out. I believe that if you install a new check valve it will solve your problem. I had the same issue with my Benjamin marauder.

Ive thought about just replacing the whole valve assembly. As far as debris go I've cleaned the whole valve assembly as well as the tank each time with no change. I questioned the valve spring being weak also but hatsan said that's not possible.

 

[willy]

YEKS" i hope ya find it?i have the same gun"mine's been worken fine"

 

[KatoKevin454]

you may have a scratch or dent on the sealing surface, you can try to polish out the sealing surface or easier to replace the valve end, lube the O-ring with Silicone oil or grease before installation.

 

[xyon]

I agree with KatoKevin454, A defect on the surface the o-ring seals against may seal at high pressure as the o-ring is squashed enough, but when the pressure drops a channel for the air leak opens up.