The pre-1980 Scorps had a vent hole in one of the bolts that hold the secondary in place. Basically it let let the chaincase vent right on the brake. These things had a poor enough brake without putting oil on it. In 1980 they put a roll pin and hose on it.
The way to do it on an existing one is like this. Drill the vent hole big enough for a small roll pin. You don't need to drill all the way, just enough to get the pin in securely. Take some 1/8 inch fuel line hose and route it down below the chaincase. Remove the top to rear bolts and put ones in that are long enough to thread through the back and put wire holders on them with a lock nut.
You could put them on the front if you had metal clips that will allow you to tighten up the cover. I originally had this, but it doesn't let you tighten the cover up like it needs to be.