You should be able to get it close by just loosening the adjuster bolts and then manually turning the engine over. This is the method described in the manual for the 79. I believe that the engine idling method is described in the appendix for the 81.
That said, I'd plan on readjusting once you get it to idle, so unless the cam chain is super loose I don't know if I'd bother until you got it idling.
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals
My wife's recipe website that I'm trying to help promote:
Strawberries for supper. Yes, I am a lucky man.