Welcome to the site !!
I am a little lost as to what bolt you are referencing , the #5 looks to be the Decompressor arm ,, what year is the bike ?? , so I can look at the parts Fiche , if the bolt is within the valve cover , it would be covered in oil , so that is why I am confused .... if you were saying it was the 2 bolts on the left side of the head at the base , then I would say it is a head gasket , but need more info here , or better yet , a picture of the actual part where it is leaking ........ hard to decipher what is going on when looking at a Fiche rather than the actual part .........