Yugo m59 and romanian dont have the gas valve likethe yugo M59/66 does.
If it did you would also probably see a grenade launching sight attached to the front sight block.
Here is a link to a picture of a 59/66 notice the grenade launching attachment on the muzzle.
http://www.aimsurplus.com/acatalog/Yugoslavian_Model_59_66_7_62x39_SKS_Rifle.html
To fix any gaps between the tube and the gas port coming out of the rifle.
Make sure the connecting surfaces are flush against each other.
If their flush but a gap exists because tube length, then, you can add a shim to the side of the tube contacting the rear sight block.
Or, you can buy a new gas tube from Tapco
http://www.tapco.com/product_information.asp?number=SKS6632&back=yes&dept=178&last=9
These are made to sks specs.
The yugo 59 sks's were shot with corrosive ammo (brass cased yugo ammo)
in the former yugoslavian military. Your yugo might have a corroded gas tube end near the gas port. Some of them have really bad corroded gas systems.
The yugos don't have the chrome lined barrel or gas port that you may have seen on other sks's like some of the chinese ones.
Zastava the company that has made the yugos and still makes them, has a new marketing agreement with remington to sell new rifles soon.
Hopefully, remington will also sell new sks rifles.