heres an easy check ebfore yo go to the trouble of pullin the clutch cover. fill the coolant all the way up, if its not already and ride it. see if the coolant level in the rad goes down. if it does, then yes you have a leak somewhere. if not, then its something else..when u drained the oil to change it, was there water in it?? i doubt that all of a sudden with this new oil it would have made it leak. if its leaking it would have already been leaking...was there water in the old oil??