Model C stiff gear change

The gear change on my model c is rearly stiff not smooth I know it's only single cable where the D and LD 150cc's had twin cable on mine you have to force it into 1st gear then rearly stiff getting into 2nd when the gear selector says 2nd you not actually in 2nd is there anyway to make the gear change smoother the book of thelambretta says cable required lubricating should I give that a go or is there somthing else I can try