I have a Chopper with a 1970 TR6R powertrain, anyways, I have an aftermarket oil tank that has 3 fittings, one for the feed, one for scavenge (including a "T" for the rockers) then one that appears to be a vent/overflow, all on the bottom of the tank, the scavenge and feed are where they are supposed to be and function normally. This other oddball fitting dumps oil when you shut the bike off,or under hard running! so i plugged it off and the cap blew off!(i lost it by the way.) after the caps off,no dumping or pressure. no leaks. I bought another cap, routed a line from the odd fitting, figuring its a vent or something, higher than the oil tank under the seat,and rode for 15 miles oil belched out on my black cherry fender and my right leg!, so i removed the cap, drove home again and all was well. this appears to have a functional use ,for what i do not know, its not a chain oiler, right now I added a vent tube to my cap to solve the problem, anyone ever seen these? does it have to do with OIF versions? If its supposed to be there where does it go? never seen one before.