Good luck mate, same thing happened on my old yamaha, replaced head gasket for 150 bucks! If your gonna replace that, may as well replace water jacket gaskets and clean out the water jacket as well, get rid of anny build up of salt over the years, no matter how much you flush em, you will get some in there, and once its gone, you will notice a massive difference in water flow from your tell tale! Have fun mate!
Sent from my SM-G900I using Tapatalk