A friend has one that is FTE any tips on running it ? It does have the grenade launching sights, what position does the button need to be at to run semi and not single? YES, it is clean !!!!
There is only semiauto on a neutered AK and that is all the way down.
I guarantee that the problem is the grenade launching sight. I have seen it before. Basically the sight is not only a sight but a valve handle. The round part that just looks like a hinge for the sight is actually kind of a valve. It has a hole drilled in it.
When the sight is up the the gas is closed off to the piston on the bolt carrier and all the gas comes out of the barrel for the grenade. That will cause it not to cycle correctly.
When the sight is down the hole is lined up with the hole in the top of the barrel and allows gas to go to the piston and it cycles correctly.
I saw someone take the grenade sight completely off leaving a giant holes in each side of the block where the valve (hinge) for the grenade sight was causing all the gas to escape and not to cycle.
And who knows it could be put in ass backwards if that is possible? Or turned halfway. It has been a long time since I had a Yugo.
This is the reason AKs have a bad rap. It could be something your friend did or most likely something done at the factory when they reassembled it.
Problem is the gas valve where it contacts the gas tube. The valve is worn out from corrosive ammo. There are a couple of vendors that sell stainless steel replacements at reasonable prices. Easy way to check is to do the 'paperclip test'.
Straighten out a standard paperclip.
Bend/shape it around the gas tube as a guide so it's nice and round. Or use a drill bit or dowel rod.
Trim as required to get s snug fit in the forward end of the gas tube.
Install gas tube/hand guard and go test fire a mag full.