Attached hopefully is a concept drawing for a manual cam chain tensioner. The design utilises a standard cam chain tensioner containing the standard spring but with the ratchet mechanism removed. It has  Verslagen roll pin mod to prevent the plunger coming out. An extension is added to the plunger as per the Verslagen mod to allow for the second hole option but the extension is made longer and a third hole provided to allow a rod to be attached via a pivot which runs to the front of the crankcase and exits through a spigot. The spigot has a pinch bolt to capture the rod and prevent it moving once the tension is set and a locknut to prevent the tensioner from moving back. To set the cam chain tension the pinch bolt is released which allows the standard spring in the tensioner to set the tension. The pinch bolt can then be locked to hold the  tensioner in position and the locknut run up against the face of spigot to prevent the tensioner moving backwards in the event the pinch bolt becomes loose. If required the locknut could be moved forward slightly and the pinch bolt released - this would allow some small movement backwards to compensate for the expansion of the engine which apparently causes the cam chain to be over tensioned. This is a very simple design that anyone could make without any problem. However I have never had the crankcase cover off so am not sure if clearances would allow for it to work. Please comment!

Thanks for the feedback DesertRat. Yeah, it could be close in there! The idea is really just a thought bubble and I am hopeing that it might kickstart some thinking on ways that a manual adjuster could be done. There is a lot of experience on this forum plus people here seem interested in working problems out and trying out ideas!