No answer for you here, but I had a similar problem a long time ago when I had a Harley. The garage floor was spotless under the bike with no signs of a leak. At work, more often then not, there would be a little puddle of oil under the bike. One day the puddle was red?!?!? Come to find out my buddies at work were messing with me by putting a little oil under the bike. The day it was red was when they used transmission fluid to dribble under the bike cause they ran out of oil.