Yes, but I am referring to when do you let the rubber bands back down, was this always common knowledge back in the 70s? The service manual mentions nothing about being careful with the valves during reassembly. No warnings or even a passing remark about it. I believe it to be true, since so many people have mentioned this trick here, but just want to know more detailed information about it.
That manual also doesn't mention anything about not dropping the engine on your toes, but you wouldn't do that, would you? Ofcourse you must be careful not to bend any valves, or your bike won't run. For me that falls in the category of "do not dry your cat in the microwave".
I've never used the RB trick, but its very simple, with the valve cover removed, hook a rubber band under the rocker through the opening, stretch to the opposite valve and do the same there, repeat with all valves, and they will be kept out of harms way while you screw the cover in place.