When I change the oil and filter on my 90 FLHS, I notice that everytime I change the filter (harley davidson black OEM filter) that there is never much oil in it. It mounts under the transmission in a position where I would think when you unscrew it and turn it upside down, that oil should come out. But amount is very little. Does anybody else have a 90's big twin with filter mounted under trans? Is this normal?