Is that Kohler breathing.
Sounds like the crankcase isn't being vented.
That would blow gaskets, or the dipstick.
Valve cover is a two-piece affair, with a foam filter between the inner/outer shells, vent tube connects to air filter housing. I cleaned the foam filter and checked the vent tube for obstructions and the air filter housing. It's a known Kohler issue, they put the muffler about 7 inches beneath the valve cover and the heat goes right up to the lower part of the valve cover - piss-poor engineering right there. Plus, the valve cover has uneven-spaced bolts, allowing for (encouraging?) the cork gasket to leak in that same area. Other than that, it's a great engine