russia is suspicious of china only because of its defence secrets being stolen....on strategic issues they are on same page....
russia will go where money is....if china wants to buy weapons i doubt they will say no to them...unlike US which will[or may be cant] sell weapons to china....
dude...as 1962 is a past...so is 1971...many things have changed since them.....
Russia is "allies" with China for only one reason: to deter the U.S. This is the one common enemy that they both have, and their "alliance" is based entirely on this.
Russia realizes that China is no longer a reliable arms market, because the Chinese simply reverse engineer everything they buy. If you ask me, the Su-30MKK deal is the last major Sino-Russia arms deal. I will be very surprised if Russia decides to sell PAK-FA or its derivatives to China.
Russia is suspicion of China goes beyond just stealing defence secrets. Back in the Cold War, China actually allied itself with the U.S. against the USSR. But as soon as the USSR collapsed, they went back to supporting Russia. Bottom line is that China goes against any country that is stronger than them, because they view themselves as the sole country that deserves international hegemony.
Also, Chinese illegal immigration into Russia's Far East is a huge problem. Russia's population is small, declining, and aging, and there is little they can do about it. Within a decade or so, there will be more Chinese in Siberia than ethnic Russians.
I know it's not 1971 anymore, but Russia is still our ally. It is not, however, our only ally. We cannot complain about Russia's relationship with China when we ourselves are becoming close with Russia's rival, America. That's just how politics works.