Marui M870 gas leak

[Trouble]

Has anybody encountered problems with the Marui M870 leaking gas? When the gas tank is inserted the gas blows straight out in a constant stream into the gun without the trigger being pulled.

It was purchased new a couple of weeks ago, is under warranty, so the shop should swap it straight for a new one, but wondering if anybody has heard of or seen this problem?

[BioShocked]

Re: Marui M870 gas leak

I had a similar sounding problem dude, it's the gas tank. I bought a new gas tank and it fixed the problem, so could be a seal problem.

[Trouble]

Re: Marui M870 gas leak

I had a similar sounding problem dude, it's the gas tank. I bought a new gas tank and it fixed the problem, so could be a seal problem.

Cheers, going to drop it off at the shop this week, if it is a faulty tank they should swap it for a new one, fingers crossed that's what it is...

Thanks for the reply.

[B.E.N.]

Re: Marui M870 gas leak

Make sure the O-ring inside the stock is in place... (remove the gas tank, then the stock to check this) It can get blown off by releasing the tank when it is pressurized.

Secondly ensure the outlet valve is working freely. Spray a little silicone onto it, prod the inner part of the valve with a piece of dowel or other blunt object and rotate it a little... This should ensure the valve is lubed and moving freely

[Trouble]

Re: Marui M870 gas leak

Make sure the O-ring inside the stock is in place... (remove the gas tank, then the stock to check this) It can get blown off by releasing the tank when it is pressurized.

Secondly ensure the outlet valve is working freely. Spray a little silicone onto it, prod the inner part of the valve with a piece of dowel or other blunt object and rotate it a little... This should ensure the valve is lubed and moving freely

Thanks, will try that later...

[mr lean 81]

Re: Marui M870 gas leak

Got the same issue with my one! Will give the retailers a buzz b4 I start tinkering

[mr lean 81]

Re: Marui M870 gas leak

Retailer has none in stock to swap anyway... any take down guides about?

[mr lean 81]

Re: Marui M870 gas leak

Decided to take it back rather than to bits. Will see what the shop think.

[Trouble]

Re: Marui M870 gas leak

Sounds exactly the same problem. Hmmmmm, bad batch perhaps...

[mr lean 81]

Re: Marui M870 gas leak

Retailer fixed it, said it was a dry seal in the mech. So you should be back up and running soon enough.

[B.E.N.]

Re: Marui M870 gas leak

There's definitely a plus in not allowing the tank to empty.

[mr lean 81]

Re: Marui M870 gas leak

Mine went faulty whilst half gassed up and not being used? Go figure? It got totally soaked at serial 40 so can only think water got in somewhere it didn't like.

[Stormshaddow]

Re: Marui M870 gas leak

Mine had this problem- not the tank but the o-ring that is in the middle of the internal reservoir in the gun itself. Basically there's a bullet valve type setup in the gun that when the hammer hits releases gas from the rear portion of the cylinder to the front out through a hole sealed via an o-ring. If this o-ring perishes then there's no longer a good seal and gas passes straight through! I purchased countless boxes of mixed o-rings before I realised that it's a bespoke size- ordered off eBay the right one it's 3.63 I/d by 2.62mm cross section. I have spares if anyone needs one!

[Stormshaddow]

Re: Marui M870 gas leak

Ok so I've also had the issue with the stock gas 'nipple' o-ring blowing off when releasing the gas tank under pressure. I've already returned it once to the retailer after the oringinal first o-ring split, but now having ordered sets of the correct diametero-rings I'm getting the same issue of the first oring blowing off under pressure, this didn't happen with my last m870- so could this be a bad batch? I have replacement o-rings now for the gas nipple inside the stock, and also a full set for the output valve in the tank -if anyone needs a set let me know!

[Stormshaddow]

Re: Marui M870 gas leak

Ok so here's the fix- for me anyways- check that the release valve inner o-ring is intact and properly seated, then with the stock nipple- the part the tank marries up to- put a larger o-ring on the groove nearest the front of the gun and the standard size on the rear o-ring nearest the tank. This ensures that the gas released by removing the tank under pressure is dissapated and the nearer the tank o-ring can't get unseated or split. JOB DONE! If anyone needs these replacement o-ring hit me up!