Would have been nice, if Honda would have made a 175cc single instead of a twin, so they (and we) could have used the pistons in the CBX 
Along these lines, I have wondered for some time, who made the multiple cylinder bike with the smallest pots. As far as streetbikes are concerned, of course, a twin should win that tilte.
But what if we exclude twins? So far, I came up with Kawasaki's 250cc triple. 250cc over 3 cylinders makes roughly 83cc each. And does anybody know of anything smaller than Honda's 125cc five-cylinder racer?
That's just 25cc per jug. For a 4-stroke! 
I just recently had a couple of exhaust valves for a 50cc Honda single. Talking about miniature machinery....