| Mark I thought I would put my answer to your PM here as others may want to comment or take note
"Yes the Breather comes through from the underside of the tank, the other is the drain to stop rain water building up and then getting into your fuel every time you open the cap
On the underside of the tank on my 750 Monster they are marked Bleed and Drainage respectively
These can block up and I have had to use welding wire to clean them out before
The Drain is outside of the fuel cap seal so under normal circumstances shouldn't see petrol other than when over filling or being a bit sloppy when filling . The bleed should come up to a small rubber grommet like thingy that lines up with the breather in the standard filler cap which should contain a one way valve so no catch bottle needed
Most cheap Aftermarket filler caps fitted to Ducatis are actually Yamaha ones and the breather is in the wrong place to align with the bleed on the Ducati tank.
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