Yep, mine does the same, I just every couple months drain the drive tube into a graduated jar, and the final drive overflow into the same (just to make sure it adds up to the total, in my case for the Mono, 150ml), and pour it all back into the tube (I use synthetic). It can also flow into the gearbox believe it or not, so if the amounts don't add up, open the box level/fill plug and check for overflow. Mine never seems to migrate more than 50ml to the final.
Eventually when I get my other bike on the road, I will permanently repair the seal, but as I use the bike daily (read 12 months a year), I'll live with it for now, I'm not really lazy!! LOL
Bill.......................;-)
