Q: How can I solve the oil leakage through the gasket seperating the crankcase from the cylinder block?

A: One thing to remember is that the gasket between block and crankcase should be glued on with a suitably strong adhesive and the bolts should be torqued up to the correct value (this is not trivial because you need a special spanner with an offset handle to do that otherwise you cannot clear the restricted space).
- Andrea -