So I got my m70 back from the smith yesterday and shot it - the first 10 or 15 rounds wouldnt cycle, but after that it ran fine. So correct me if you think I am wrong but it seems the gas bolt is defective and letting gas out when its cold, but once it warms up and expands some it makes a better seal?

I put in the gas bolt that I got off gunbroker and it fits way tighter than the one that came with the gun.  I tried to install the one from Century that they sent me but its not for am m70 since it wont even fit in the gas block.

i was also shooting hp's but they cycled a-ok after the initial run through each mag with a few rounds. I thought it was a mag problem at first but the second time I went through my 9 magazines they all functioned ok.

I have purchased to rifles from century and I had problems with both of them. Needless to say, they won't be getting anymore of my business.

I had the same problem as you but it was fixed after century returned my rifle to me 6 weeks later.

AKs don't like tight tolerances.  If the piston is tight in the tube then it will not function properly.  Also things like quadrails have been known to bind the piston (UTG had one that did that for awhile).  Without more info it's hard to say exactly what is causing your problem, but so long as the gas block and tubes are surplus I would doubt very much that they are the problem.  My guess are mismatched parts.  The Yugos are completely different than most out there and you need to make sure you get the right parts.  Gunsmiths come to build groups for answers on these things and I really have not found any competent gunsmiths when it comes to building AKs (ironic, but I have several gunsmiths and none of them have ever built AKs).  So I would hit the build forum for significantly better help than you will find here.  

Ill keep that in mind :D.

I found a guy local that seems to know what hes talking about but I *think* I might have found the real issue here. When I first got the gun I polished the bolt carrier and hammer, but never noticed anything weird about it (I was having cycling issues). I replaced the gas cut off bolt and had it serviced by a smith, which seemed to help - he got it running but only when it was warmed up. The gas bolt seemed to make it work all the time, probably 90% as of now.

Last night I decided to polish more and noticed a burr on the hammer, that I removed with a very very fine polishing stone. I followed up with some other polishing with the dremel and its much better but needs more polishing. I ran out of time last night, but as of now I can move the bolt slowly fowards and it wont bind. It does a little in that same spot but much better than before, I dont know how I overlooked this thing...

Check to make sure the gas block and gas port in the barrel are lined up correctly.  Century installed the gas block on a new barrel, so they may not be lined up giving you too little gas pressure to make things run. Even if your gas shut off is leaking a bit it should have plenty of gas to run.  Also, if you are feeling some dragging when the bolt carrier is moving back and forth check to see if the receiver rails are too narrow and are squeezing the carrier.  Remove the bolt and cycle the carrier without it.  If it runs fine you know it is the bolt dragging on something like the ejector.  If it still binds up look for wear marks on the upper rails and the carrier.  If you see some you need to find the spot on the rails that is dragging and file it down a small bit. This is all assuming that the bolt is not going back far enough to extract, eject and feed a fresh round.  If it is ejecting fine, but not feeding due to the bolt not going foreword I would swap out the recoil spring and see if that helps.  If you want IM me and we can discuss what is going on. I am not a smith, but I have worked on these things for some time and have seen lots of odd problems.  Let me know if I can help.