I spent last Saturday replacing the scooter's head gasket and did every trick I know to make it bulletproof. It didn't work. The scooter is still leaking and will require replacing the cylinder head, cylinder and piston to make the engine oil tight. I'm not amused.
Today I removed the cylinder head from the Yamaha and the news there is even worse. The valve broke off inside the engine and wedged itself in the exhaust port. On closer examination the camshaft is worn and the rocker arm that opens the exhaust valve is worn out. New parts will cost over $400, more than the bike is worth. I have a call in to a cycle salvage yard advertising a used cylinder head for $50 which is much more my speed. Stay tuned.