Sometimes you do it because you can. Here's a company, Dolmar, that makes chainsaws and they decide to build a motorcycle powered by 24 chainsaw engines, the Dolmette. It's a blending of reality and a German comic strip character. The result actually runs, though starting is a bit of a chore with 24 pull starters. The power is delivered through a belt drive system that feeds it to a Harley 5 speed transmission. Each engine is 79cc and combined power is 170hp. There's video on the site. Pretty cool.