Thank you for the replies. The copper washer is between the head nut and oil outlet in the photo. When I rebuilt the engine I mistakenly put the washer betweem the outlet and the head. Didn't realize I had installed it incorrectly until I investigated this issue and have since corrected it. The oil tube is clear. I am able to pump oil through it with a little oil can. The picture of the outlet and washer was after I had tried to seal it with RTV which didn't work. I carefully scraped the gasket off and used scotch bright pad to finish clean it. I have attached a photo of my original head off the tractor. Same part number as what is currently on it.