Thanks to the forum guys who contacted Kenny cycle X re the tensioner, he said you folks alerted him to my email.
His instructions were as I posted , , put slack in chain to the bottom then screw in until firm, then back out half turn.
thanks all.
So got the carbies on, took longer than I planned (two nights) I modified the inlet rubbers to make sure they were 32mm all through ( up from 29mm ) to match the ports Mike.
I was going to start with the base tune of 31mm but no time for dyno now so I put in the 32mm chokes and matching jetting, the carbies were looking good, been almost 40 years and still like new. , made up a support for the carbies , had to make custom cables from CB 450 honda.