Hey lisa, a mid sized bike should be easy to find used here, no need to go anywhere else. His best bet is the site at
http://www.segundamano.es/sm/motos.htm and specifically the pages at
http://www.segundamano.es/scripts/SMPorIndice.dll/sm/motos.htm?idsec=3031 for bikes up to 500cc.
I just checked it out and today (August 1st, 2002) there are 525 used bike ads in that category alone

That is for all of Spain but if you use the search options at the top of that page you can limit your search to Madrid only
![[search]](graemlins/search.gif)
For my search it shot down to 113 ads for used bikes up to 500cc in Madrid, still quite a few.
Also try the section at
http://www.aceleris.com/busqueda.asp?inIdFamilia=2 and use their search criteria to find what he is looking for. I got 261 ads for Madrid alone.
Your beau should keep in mind that "motos" (either small scooters or big bikes) are a huge target for theft here, much more so than cars. My last 2 friends (both ExPats, one from the U.S. and the other from England) to buy bikes had them stolen from under their apartment balconies within 5 days and 1 month of the purchase, respectively
I do not know that there is any way to avoid having your bike stolen as locking it up is usually not much of a deterrant. One way may be to rent a "plaza de garage" (garage space) for it since most of these garages for rent have security guuards and are private and well lit. A "plaza de garage" for a motorcycle usually runs between 40 and 70 Euros/month depending on how close to the city center it is. In Madrid (as in most cities), price naturally goes up as you get more central and also in the more "ritzy" areas of the city.
Food for thought, please let us know on this thread how it goes and if he ends up getting a bike here. This is an original thread and it would be good to get your first hand feedback for others interested in having a bike here in the future.
Saludos,
jer...