Tell me you want to go back to those days ? PCV & CAT may have had some birthing pains, but, the LA basin would be inhabitable by now if it weren't for all that "green crap".
Nah, I don't wanna go back, however, the BS of burning alfalfa in our gas is not doing anything but costing us money and unreliability in our fuel systems. that is the "green crap" I am speaking of. Now as for a few RE's removing a breather pipe, my comment still stands. Let's not turn a few REs into an international incident! On the other hand, I don't hear anyone complaining about losing their torpedo tube and catastrophic converter! and as I noted in my original comment, I like the closed breathers on cars. As I said then, they have really cleaned up the center of the lanes that used to be grease and oil striped. Busted my butt on that once!
As for the UCE breathers, I don't recall any one way valves on the UCE external breathers. There may be one going into the little breather compartment in the crankcase itself, or the compartment may be serving that purpose. The tube from the crankcase to the end of the seat worked quite well with nothing on the end on Jack's and my bike for a couple for years. There was never any oil up there. Never had any oil leaks in the engine. Never had any performance problems. Never used any oil to speak of. I considered putting a duckbill on mine, but never saw any need for it. The length of the tube probably offered enough back pressure to take care of whatever was needed. There were absolutely no downsides to it at all.
If you drop the bike on its right side, you might blow oil out of it, but you'd do the same thing with the original layout, except you screw up an air cleaner that way. The way i did it, you pick up the bike and ride off.
Bare