This article is from the Ducatis Motorcycles FAQ, by Duke Robillard email@example.com with numerous contributions by others.
Thanks to Julian Bond for some of this
Unless it's a lot of oil, no. If it IS a lot of oil, the concern isn't that
the breather is having a problem, rather that there's excessive blow-by,
say, from a damaged ring or similar oil-retaining device. Most Ducs tend to
mist from the breather a bit because it's a small crankcase volume for the
displacement -- translate: high crankcase pumping action. California bikes
get a more proactive crankcase ventilation system so they tend to stay a
Also, the seal between the breather assembly and the crankcase is not very
good as the breather is plastic and deforms easily. One thing to try is to
Unscrew it and carefully clean everything and then use instant gasket on
the breather and washer.