Check prior to cylinder head removal
1. Crankcase overfilled.
2. Oil carryover.
3. Breather hose restricted.
4. Restricted oil filter.
Check after cylinder head removal
1. Valve guide seals.
2. Valve guide to valve stem clearance.
3. Gasket surface of both head and cylinder.
4. Cylinder head casting’s porosity allowing oil to drain into combustion chamber.
5. Piston/ring failure.