Leaking transmission seal

[drost]

I have a 93 RT and the output seal on transmission is a leaker. Transmission has been rebuilt and am on my second seal with no better results. The first seal came out pretty easy and installed the second seal with a scum of Ultra Grey on the outside thinking that oil was weeping around the outside of the seal. Same results, boot filled up with oil. I removed the swing arm (mono-lever) and ran in fifth gear to see where the leak was. Appears to be between seal and yoke. Seal is installed correctly, vents are not plugged, and the sealing surface on yoke is like new. I see that the (GS) para-lever swing arm uses a Teflon type seal in the transmission which in my opinion is a far better seal. Can anyone tell me if they have used this seal in a mono-lever or is there something I’m missing? Would also like to know why BMW uses different seals on the same transmission in different bikes. The sizes of the two seals are the same.