Mine did that as well after some time , I think lots more do it than we want to admit. Sounds like it's time for a new gasket , if it's still under warranty , let the dealer fix it .

Hmmmm , now I though only Harleys leaked oil.

2005 Model . Two Fast Eddy stickers , a bell and a clock . She's Lola . She tinkles and keeps time . http://s649.photobucket.com/albums/uu211/britbike05/