Leakage Between Cylinder Head & Cylinder Block

Hey guys,

i have a leakage between the cylinder head and the cylinder block. The engine has been taken apart. The gasket in between the two looks fine. What else may be causing this leakage?. I dont want to simply replace the gasket and then see it leaking again. Someone else mentioned it might be the o ring seals. Don't really know how they look or where about their located. Any suggestions guys, really want to finish this job. its a x7 110cc pocket bike.

thanks again