Taking apart a Mares Sten 11 that has been inactive for more than 5 years.

[MurkyWaters]

Hi Everyone

I've recently gotten my hands on a barely used Mares Sten 11 that has been inactive for more than 5 years.

I'm thinking it would be smart to check the o-rings and give it some oil, but I'm having a hard time finding any documentation on how to take it apart and do this step by step online.

Does anyone have a link to a guide or some good advice for me before I hazardously start winging this journey

All the best

- MW

 

[tromic]

Here is an video, Mares Cyrano, might help:

 

[popgun pete]

https://forums.deeperblue.com/threads/pneumatic-dismantling-how-to-get-inside.90024/

There is no real reason to dismantle it as five years not being used is nothing, guns can sit for years without being sold in stores. If the piston feels stuck then let the air out to move it, sometimes the seals can stick if not moved for a long time. Lubricate the gun first by dunking it in water, either end will do at a time using a bucket or small tub. This wets the external surface of “O” rings in the gun.

 

[Zahar]

If the barrel turns, it will be like this! He forgot to take out the pressurized rod!

 

[Zahar]

https://forums.deeperblue.com/threads/pneumatic-dismantling-how-to-get-inside.90024/

There is no real reason to dismantle it as five years not being used is nothing, guns can sit for years without being sold in stores. If the piston feels stuck then let the air out to move it, sometimes the seals can stick if not moved for a long time. Lubricate the gun first by dunking it in water, either end will do at a time using a bucket or small tub. This wets the external surface of “O” rings in the gun.

If the gun has stood for 5 years without pressure in the receiver, then the skirt of the piston collar will sag and move away from the barrel! You have to take it apart and see! After 5 years under pressure without work, the rubber sticks to the barrel and breaks at the first stroke of the piston!

 

[popgun pete]

If the barrel turns, it will be like this! He forgot to take out the pressurized rod!

This is explained in the referenced thread when discussing removal of rear handle from inner barrel, it pays to read all of it.

 

[popgun pete]

If the gun has stood for 5 years without pressure in the receiver, then the skirt of the piston collar will sag and move away from the barrel! You have to take it apart and see! After 5 years under pressure without work, the rubber sticks to the barrel and breaks at the first stroke of the piston!

Not necessarily, I have worked on many Mares guns and few have had troubles with piston seals sticking. He needs to pressurise the gun and see if the piston moves without any air leaks. No point in opening a gun up if it does not need it. Changing the oil needs the gun fully depressurised and the muzzle removed and then the piston to allow the oil to be poured out. Even if the oil looks OK it may as well be replaced. The muzzle screw threads need to be greased before the muzzle is replaced and tightened up.

 

[popgun pete]

The “Sten 11” is the new name for the “Spark” speargun. The original “Cyrano” was the first gun to appear with what was to become the “Sten 2001” handle and had an 11 mm inner barrel and a long narrow snout on the gun. Mares replaced the snout with the usual front end, lengthened the main tank and that became the “Spark”. Then it was renamed “Sten 11”.

 

[MurkyWaters]

What a treat to come back from a great weekend outdoors and find a lot of good advice here, I'll take a look and see if an oil change is all it needs before taking it completely apart.

I'll also make sure to check out all the links, thanks a bunch everyone.

 

[popgun pete]

Because “O" rings can take a set in a position including draping over any surface imperfections such as a mould parting line in the plastic it can be that they will not fully seal again unless back in exactly the same position rotation wise. Usually they will, but if you go to all the trouble to pull the gun apart then you may as well replace all the seals. Ironically by disturbing them you may have compromised the gun’s sealing, but most of the time you won’t. This really applies to guns that are over a decade old as guns that have only been constructed in the last 5 years the rubber in the seals will not have hardened through aging.

I have found larger “O” rings such as the body rings were twisted when installed on the gun as the mould parting line on the rubber ring is twisted and the ring will not straighten up due to friction once installed. The tank or body tube will often flatten the ring slightly and those flats tend to remain. If the rings are still pliable then they will accommodate being squashed in a new position and may even regain their shape after time sitting on the work bench or in a parts tray.