greg bender
http://www.thisoldtractor.com/gtbender
When dissabling the stock breather valve (to use a different style check valve), in my opinion it is very important (read: vital) to remove the spring and washer inside.
Thanks to Kim Schick who posted this information on the Yahoo! Loopframe_Guzzi news group. In Kim's own words:
I need to chime in on the breather box thread that was going on a while back...
A Dremel tool cuts an excellent "piggybank" slot on the bottom of the box and lets you fish the "washer" out.
Brazing the slot allows for powder coating, but JB Weld works just as well (so far at least) as long as you're doing the paint thing.