As the post in tricks and tips has dropped a few pages I will once again give the workshop 40 year old instructions:-
(1) loosen the locknut so it is free
(2) loosen the pinch bolt
(3) put weight on the kick start, or on a spanner on the big nut on auto advance so that the engine is just about to turn in the normal direction of rotation----this puts all the slack in the rear run of the cam chain where the tensioner is
(4) whilst holding pressure on the kick start nip up the pinch bolt then the locknut.
For this to work the tensioner needs to be working, the tensioner rod must not be burred and there must be life left in the chain.