I’m not really a two-speeder type, but can confirm that there have been two or three different ways of rigging up a hand clutch, perhaps better called a neutral finder, rather than a clutch to be used for starting off from a standstill, although I have an idea that one method did give this facility. It would take a trawl through old Yowl indices to find the articles, but I can remember that one idea came from a man called W.C.Fox, and another from the journalist ‘Wharfedale’. I think, (not too sure), that George Reeves also devised something similar. The obvious way to do it would be to connect two cables to the gear pedal boss, so as to give a pull onto the drum in either direction, perhaps operated by a double-cable twistgrip on the L/H handlebar.
Brian