Hello, I attached some photos of the breather setup on a fxsts I recently bought and I'm not sure what the silver cans on each side are for or who made them...I did also have some oily buildup behind the carb backplate and around the breather bolts.

 

Interesting setup. The cans are either small filters or checkvalves. The oily buildup behind the backing plate is normal, due to how The MoCo designed the whole thing to seal to the heads. You've got an aftermarket carb bracket on there, it may have a pair of o-rings where it mounts to the heads. Check to see if it does. You could add a couple fiber washers to help seal it if not. If the cans are restrictive or clogged, it could also be contributing to excess oil leakage.

 

It's a breather by-pass. To keep the oil OUT of the carb. The cans need periodic cleaning.

 

They are check valves and do need periodic inspection. They are usually installed when the umbrella valves in the rocker assembly's fail. Easier..

 

And, If used in addition to Umbrella Valves... they Inhibit free Breathing... something we avoid at all cost in my little world, almost as bad as Inhibiting return Oil!!!