New to working on tractor. What is the purpose of two oil fill ports on the valve cover and a third on the assesory cover on my YM 1600? I figured they must use this valve cover for other applications so I change the oil today using the fill port on the assessory cover, then cleaned the tractor. When I started it, I found an oil leak from my valve cover gasket, and it was definitely not fresh oil. Is it just a couple ounces of old oil that didn't drain out of the valve cover, or is there another oil reservoir I need to attend to?