Removing the fuel cap lock barrel out from a Ducati fuel cap - in this case a recently purchased spare part for a 916.

I'm starting the process with the cap locking pin and cap seal removed, because that's the easy part and I wasn't thinking too much about photos.  I do have a Youtube video about fuel cap reassembly.  Does Youtube let you play videos in reverse?  That'd be handy.

Anyway, once you've got that shit off, slide off the silver washer you can see in the blur at the top of the photo, the cap seal and the 4 springs and you're left with this:

That's just a thin washer.  Remove.

Then there's a black o-ring.  Remove - I had to use a wee pick to get under it.

Under the o-ring is another steel ring, this time much thicker and harder to get out.  Strong magnet is probably the best bet.  Maybe not banging it on the bench hard.  You don't want to wreck anything.

And then, you get to the important part - the little lock tab.  The gold bit in the yellow circle, in case you're not familiar with this sort of thing.  This is what holds the lock barrel in.  Get in there with the wee pick, push it in and the barrel will slide out the other side.  Having a key in the lock is a good idea, that way all the wafers don't spring out and piss off and cause a tanty.