First off, I have a Chinese sks that I have put back together before.
Last night, I took it apart and cleaned and oiled it. I put the gas piston back in and locked the lever down.
Then I put in the fixed mag and fastened in the trigger group. Then I attached the bolt to the bolt carrier and
slid them into the receiver. Next, I pushed the recoil  spring in the back of the bolt carrier. Here is the problem.
The receiver cover will not push in far enough to get the receiver pin through. Any thoughts on why this time
the receiver cover will not fit flush with the receiver? I can't figure out why all of a sudden it will not go in far enough.

I even took it apart again and put it back together again and still a no go. I'll take any suggestions you might have.
Anyone else have this problem?

It could be one of a couple things I think.  First I'd make sure that the bolt is fully in battery, make sure the recoil spring is installed properly, make sure that the recoil spring assembly is placed properly in the cover and make sure the pin is pulled all the way out.  If that doesn't work try the above steps but with the mag floor plate open.  Let us know the out come.

Well, I guess I win the dumb-ass of the week award.My work bench where I clean my guns is not organized very well.
There is usually a pile of gun parts and other things that should be else where. When I was cleaning the norinco,
the dust cover for it got pushed up under some papers and the open lid of a cleaning kit. I just picked up the first dust cover I saw
which happened to belong to a m59/66. As I was trying to figure out why the parts would not fit,I came across the other cover.
I checked the serial # and it matched the gun. I took off the m59/66 cover and put the norinco on and it went flush and the pin locked in.
I always thought sks parts were interchangeable. Paying attention to what I was doing would have saved a lot of frustration.

Wellllllll, SKS parts are kinda inter-changable.  Sometimes you will have to hand fit parts on them because of the many different factories that were making them and the parts for them.