[Marui M870 Fix and Tuning Thread]

Thanks for the tip. Apparently this problem persisted with the previous owner where it began leaking before the o-rings were changed. I should have known it was another factor.

 

The strange thing is that I actually tried shimming the spring with an o-ring to increase its strength but the it started to leak where the firing pin engages the valve at the rear of the cylinder when I blew into it. I took it out and the leak stopped.

 

I will see what I can do about stretching the spring 130%. You could be right that it lost tension over time... Sourcing a replacement would be rare at this time.

[Marui M870 Fix and Tuning Thread]

Hey while we're on the topic of the valve there... I'm having some issues fixing mine.

 

I have a weird problem where whenever the gas tank is inserted into the stock, ALL the gas goes out the front of the gas cylinder.

 

The weird thing is that if I were to disassemble it so that it's just the cylinder and blow into where the stock attaches the receiver, the thing doesn't leak. I can't blow air into it so I KNOW it's airtight before inserting gas. I suspect it's because the o-ring is too soft and is flexing when the propane is inserted.

 

The problem now is that no matter where i switch the o-rings and what I do with the front and rear valve it still shoots out all the gas without stopping. I've even removed the "firing pin" to try and isolate the problem.

 

I hate to be a bother but could someone please post some reassembly pictures without the cylinder on? I'm stumped on this one.