You need to make a simple modification to the breather system. Simply reverse the hose that goes from the crank case to the can. Let it run straight up over the frame and then over to the can. First though, you'll need to pull the battery out and get into that oil catch can to empty it. Its over flowing and is blowing oil into your air filter.
Before doing anything, I strongly recommend some research. Read this whole thread:
http://www.enfieldmotorcycles.com/forum/index.php/topic,12620.0.htmlI ended up keeping the can, but I:
1) Capped off the timing return line at the timing cover.
2) Ran a clear hose from the crank breather, up and over the frame then to the can using the original duckbill
3) Kept the primary case oil breather, as I keep 1 liter in there to preserve the sprag gear (No problems yet, but i dont use the ES often).
4) Created a drain hose using the timing return hose with a plumbers valve on it. I can now drain the can without pulling everything apart.
Once done, I'd recommend changing the oil (if not done already as its a 'new to you' bike) and never add more that 1.75 l. Check oil after running the engine for a few minutes and shot for a the 1/2 way mark that ERC pointed out. make sure the oil fill cap is screwed in all the way. You'll get a feel for it.