Even though you may buy new cables they usually come dry so they need oiling before fitting. I was dicking about with the clutch cable for my Triumph today when someone showed me this little trick which you can even do with the cable still on the bike. Fill a little plastic bag with some light oil, (fork oil is good) then just turn it over and cable tie it onto the end of your cable, though not in that order. I was a bit sceptical but within half an hour oil was oozing out of the other end. Result.