Hello Pasty Mine was fixed by the dealer. What I noticed was that the oil seemed to travel up the head stud threads and leak out of the top. This only happened on one of rear studs. Each of the head studs have an upper and lower o ring and the mechanic thought it was one of these that had failed. In order to change them the head and barrel had to come off so they replaced all the o rings, the head gasket and the base gasket . I have done about 300 miles since and no signs of any leaking . Unfortunately when they removed everything there were no signs indicating what was causing the leak so I can't confirm if it was the o rings or something else but I would recommend replacing them because the were a couple of quid each . Hope this helps.
Question for the experienced... Do you use the sealant on both sides of the base gasket or just one side? i.e barrel side, cranks side or both sides?
