That looks like a significant leak. I'd change oil and filter or at least filter to rule out the filter, check valve cover and where oil pan and upper half meet.
After sitting for a while gaskets could have dried out.

 

Well, it can't be the OHV gaskets because Briggs doesn't install them on these things. All of the D100 series machines have engines that are assembled sans the valve cover gaskets. But that is the usual first spot for leaks.

Is it possible that the gasket on your oil filter dried out while the machine was stored?

 

Well, it can't be the OHV gaskets because Briggs doesn't install them on these things
...
that is the usual first spot for leaks.

Surely they apply some type of sealant though. Or is it just metal to metal and they cross their fingers?

I've seen carburetors with no bowl gasket but that's a different matter. A carb doesn't see the same magnitude of heat during it's heat/cool cycles that a valve cover does.

 

JD must have updated their parts system. They didn't use to show it!

 

It'll be interesting to see what the op finds for the leak. My money is on the oil filter.
I had no idea B&S (or any manufacturer for that matter) would assemble an engine without a gasket or some sort of sealant on the valve cover. Maybe that engine was built on a Monday 🤔
My wife's LX255 developed a leak between the oil pan and upper, I was surprised to find Kohler used sealant instead of a gasket.

 

It'll be interesting to see what the op finds for the leak. My money is on the oil filter.
I had no idea B&S (or any manufacturer for that matter) would assemble an engine without a gasket or some sort of sealant on the valve cover. Maybe that engine was built on a Monday 🤔
My wife's LX255 developed a leak between the oil pan and upper, I was surprised to find Kohler used sealant instead of a gasket.

I'm not sure which is worse to clean off... gasket or sealant. When I've had to remove the sump on B&S 31000-series engines to replace the cam, cleaning the stuck-on gasket material from all the nooks and crannies is a real chore.

 

Permatex, CRC and 3M make gasket remover.
Softens tough to remove gaskets and sealants.

 

Also check the oil drain pipe for looseness. Had that happen once, pulled the engine because all signs indicated a leaking crankshaft seal. Found the loose pipe while lifting the engine.
Nothing lost as the camshaft was ready to be replaced too for an inoperative compression relief. Got that done before it broke.

tommyhawk