yeah mines a small bath but not as small as some, I can do a carb body with turning it over occasionally as its not completely submerged. Dont expect miracles they arent industrial ones after all! Mine is big enough to fit a CD into. This one in fact
http://ie.farnell.com/duratool/d00351/cleaner-ultrasonic-1-4l/dp/1316381
my bike is more of a rolling restoration than a full on one, it has been rough in the past...I owned her from new and used as a winter hack for many years.
yours looks really promising I must say, should come up really nice, If you decide to do her up nice why not show us in the projects forum...it would be good to follow and try to answer any questions you might have.
Let me know about the spigot...that carb body is at work. I dont want to pull it out for nothing.