I have the same leak...now. I didn't have it before I changed the oil, but it's there now. I have deduced that it is from the rubber hose that runs from the clutch/transmission area on the left side and runs to the air box and not from the filter area. Why, now after an oil change, has oil decided to migrate up there, I don't know. I applied air to the hose on the transmission end and oil started dripping.
