1979 KZ 650D chain slack

Hello, I have a 1979 Kz 650d and when I bought it, the previous owner didn't have the owners manual. So, I'm not sure how many inches of Drive chain slack should be left on it. I know now, that it is was too loose and it needs to be tightened ,but I don't want to tighten it up too much. so as of now I'm just riding it nice and slow and just using it to get to work which is right down the street. Also, would anybody know the torque needed to tighten it to? Hell , if anybody had a copy of the owners manual that they could send by email or through shipping, I would gladly pay the shipping costs. This is my bike by the way.I would greatly appreciate the help, since it would save money.

id say around 1" in the center would be a good starting point,remember to loosen axle nut before cranking on adjusters