Seneca/Sam Yang Sumatra 2500 leak, Disassembly

[NordicAir]

Hey!

I have recently bought an Eun Jin Sumatra 2500R .22 with unkown function.
This will be my first PCP I'll have to disassemble and fix myself, before I've only owned already functioning ones.

The check valve was broken, so first thing I did was to get the Best Fittings foster fill upgrade with the non return valve.
- So atleast now I can fill the rifle.

However, I have now noticed that it leaks from atleast two places, one just in front of the receiver and the other from the upper tube end cap.
- Not too troublesome to fix I hope, there is a good teardown video and I see O-ring kits are available.

Now for the part I fear can be troublesome:
While I had the rifle filled before it leaked out, I tried to cock the action and dry fire.
I tried a few times but I would just hear the action click, no puff of air was coming out at all..

So I wanted to check here if this is a common and easily fixed problem with these, or if I have some real work ahead of me..

I will update the thread when I have disassembled the rifle and can show pictures of the inner parts and maybe someone here can identify something looking weird or broken.

Nordic

 

[SilentSquirrel]

Hello Nordic
Not an expert by any means.
But I have been thinking about the O-Rings being square sided.
I have never disassembled a gun that has been sitting for a long time.
However, it seems possible to me that O-Rings sitting in a square sided groove for an extended period might develop a "set".
And take on that shape

Hopefully others who know more about that will offer their knowledge.

Also, one way to find out might be to buy a full O-Ring set for the gun and see if any are squared,

Sorry for the ramble
Edward

 

[rdpjr6504]

Hello I have many Korean rifles and have resealed a few. I know my o rings were normal not squared. I purchased all my parts and seals/ orings from Boris at Pyramyd Air. Hope this helps.

 

[NordicAir]

But I have been thinking about the O-Rings being square sided.
I have never disassembled a gun that has been sitting for a long time.
However, it seems possible to me that O-Rings sitting in a square sided groove for an extended period might develop a "set".
And take on that shape

Ah.. I had not even considered this, the square profile is perfect on these.
It seems like the explanation to the squared shape of these!

Hello I have many Korean rifles and have resealed a few. I know my o rings were normal not squared. I purchased all my parts and seals/ orings from Boris at Pyramyd Air. Hope this helps.

Do you happen to know the specifications of the o-rings?

I suspect the ones in the air cylinders are supposed to be of 90A hardness.

It would be nice to be able to source them myself, rather than having to import a kit from the US.
The shipping and import fees alone makes the kits laughably expensive.