Oil particles from crankcase hot air vents. Normal, some oil vapor will travel up and into breather assembly. Over time the oil particles get together creating that famous oil build up. Constant inspection and cleaning is the solution.Was putting new Venom covers on my 06 FLSTI yesterday and when i removed the air filter a bit of oil ran out and dripped. Not much but is this any cause for concern. Do a lot of in town riding during the week and wondering if this is caused from bogging the engine at times. Any thoughts? Thanks in advance.