Originally Posted by Just Dave
Honda built a race bike a few years ago that was a single piston with 4 connecting rods. It was a big oval piston with 4 pin bosses underneath. I don't think it made it into production though and I can only imagine the machining to get a nice finish on the bore, plus I'd LOVE to see the rings.
In the 60's Honda also built a 250cc 6 cylinder bike. would rev to over 13,000. The bore/storke on that thing is like 1"/1"