Strick, I took my front whell off to take it to the dealer for new rubber. When I was sitting in the garage having a well earned coldy, I saw that the speedo cable (just hanging) had leaked a clear fluid on the floor. It was clear and slippery - oil!
Where the cable terminates on the hub, there must be a seal of sorts, or this oil would have gone ages ago. As your bike has been off the road for a while, you cable may have run dry. Did you have the cable disconnected for any length of time?