View Full Version : Range report on SKS that would not go Semi-Auto.

Lucky Scott
10-10-2009, 10:11 AM
A few weeks back I posted about a SKS that I built that would not go semi auto. It is a Yugo 59/66 that I put together with parts from all over, so nothing matched. It fired fine, but the spent casing would get jammed in the magazine as the next round came out. Then it would be hard to pull the bolt back because of the jam. So I posted here to get advice and got some great advice.
Heres what I did.

I was told to clean the bolt so I took the bolt apart and cleaned the firing pin and everything again really nice.

One guy told me about a trick with a paper clip where you put that around the gas valve to stop leaks so I did that.

I took a brass brush and cleaned the chamber where the round goes so it was super clean.

I added a little grease around the bolt to make it move easier.

Okay, so I go to the range and I also took a spare gas valve out of another SKS that works perfect. Thought I might swap it out and see if it helped.

I load one round and its fine.
I load 5 rounds and the spent casing is causing trouble again.

So I move the gas valve position from semi auto to single shot and fire a few rounds like that. It works perfectly in bolt action single fire. The bolt is smooth and no jamming.

I then switched from the Yugo ammo to Winchester white box and fire a few of those. Works fine in bolt action.

Then I switch the gas valve back to semi auto, and it shoots in semi auto perfectly, just the way it is supposed to.

This is with the Winchester white box ammo, so I switch back to the Yugo ammo and it still works great, shooting semi auto just fine.

I put about 75 rounds thru it without a single glitch.

However, when I got home and took it apart to clean it, the paper clip was gone! Just gone. Dont know where it went or what happened. Maybe when I moved the gas valve it broke it. Dont know. Dont know where it went?

So in retrospect, I have no idea what fixed the gun. Probably not the paper clip trick. Maybe it just needed to cycle a few rounds, I really dont know.

Works great now, and I want to thank everybody for the advice. It is a great gun to shoot.

10-10-2009, 4:20 PM
I have a Yugo M59/66 that would not cycle semi auto when I got it. I did a little research on line and found out that this is very common problem. The problem is that the gas valve is corroded and will no longer maintain a adequate seal to cycle the rifle.

The solution for this problem is to either;
1) "Oakie" the old gas valve with piano wire, electrical tape, or paper clip. I tried engine gasket sealant with good results. But this dose not really fix the problem and causes a mess for cleaning the rifle. Or....
2) Is to replace the gas valve with a new one. I bought one that was made of stainless steal so it would resist the corrosive powder residue as much as possible. Do not get a used/original one. This permanently fixed my rifle and it has functioned flawlessly ever since.

Here is a video that shows how to replace it.

here is a link to Numrich gun parts that has the valve you need for less than $15.

Lucky Scott
10-10-2009, 5:37 PM
Good advice, and thanks for the links.
I put a brand new gas valve in from Apex when I first built the gun.


So maybe the new valve is bad, but I cant imagine, since they are really a diverter not a valve. or maybe the outside diameter is too small letting gas escape?

10-10-2009, 6:54 PM
As mentioned, a good, new gas valve usually solves the cycling functions on the 59/66. But there are some cases where other things can still hamper functioning. Is there slack in the gas tube when it is in place? For example can you slide it a little back and forth, parallel to the barrel? You want the gas tube to be fairly tight against the gas valve when the tube is locked into place so it provides a tight seal. New gas valves can actually help in this area because some of the aftermarket valves are a little longer than stock.

10-11-2009, 4:18 PM
I can't remember who I ordered it from but my new gas valve was a little longer than the original one. You could also replace the gas tub if the end is very corroded. The Yugo M59/66 rifle are great guns. The gas valve/ diverter is its only weak link IMO.

10-11-2009, 5:58 PM
i'd just see how it goes. if it starts screwing up again, by all means, replace the valve, if not, shoot it and have fun. glad things worked out.