Just got done riding today and noticed a one inch crack in my head right behind the decompression hole. Bike ran really good all day,I could not tell a difference in the performance. I checked the oil and it is not milky or anything. My question is this if it is just a surface crack can I weld it and be okay? If the crack goes all the way through will I ruin anything by continuing to ride it? I don't want to buy a head if I don't have to. Also what may have caused this? Is there something else I need to fix to prevent this from getting worse and/or happening again?