Great! You caught the idea before I had finished my whining... stick it in your signature!
OK... 76 KZ900 has a MANUAL tensioner. The advantage with a manual is the pushrod is a shade longer meaning it can tension a stretched chain for a longer period of time... The downside is some routine maintenance. If you hear some rattling... it is time. You should tension it about every month, I guess. I am sure someone with a manual can tell you how many miles. At least at every oil change.
OK... there is a bolt on the side of the tensioner. It is a 6mm bolt (use 10mm socket on it). First, loosen the locknut on this bolt. Back the bolt out some. If it comes out all the way it makes no harm. The book likely says to turn the engine over a couple times using the 17mm nut on the end of the crank... I hit the starter with the coils unplugged. This finds the slackest part of the chain and the tension, which is spring loaded will go out to the max required for the loosest part of the chain.
Hook up the coils and tighten the bolt then the locknut. That is about it... I will say, one more thing as a caution. The rod inside has a flat spot for seating the bolt that holds it. At the flat spot rear is a somewhat curved area that tends to score the innards of the tensioner body. When it does, the rod can hang. Make sure when you back the locking bolt out, you feel a sort of snap... that is, you feel the rod pop out. If it doesn't, get suspicious of the rod hanging...
To remove the tensioner, you remove the two bolts that hold it. There is a gasket but it doesn't tend to leak much if reused. If you do take it out, you can pull the spring off the rod and stretch it some to give it a bit more pop...