The seal is a little (about the size of a quarter) foam "gasket". It is sticky on one side to adhere to either the inner or outer primary. My bike started leaking in the same place. When I took the outer primary off (yes, my bike is under extended warranty. However, my fix was less than the $50 deductible), I found this gasket had slipped. The dealer told me this was common after time. I did not replace the gasket. I used a 9/16 X 11 tap to cut threads into both the inner and outer primary. I then threaded a plug into both sides and topped this off with gasket sealant. Total cost for this fix (I had the tap and quart of oil for the primary) was $41.50. And, I will never have to fix it again.
BTW. It took my bike over 34,000 miles before it started leaking.