Toyota is famous for its 2JZ engine. Mazda has the Wankel rotary. Subaru gets the “boxer.” These engines have earned our respect and admiration, even with their shortcomings. Honda has its own compromised engine which was an abject failure, but ended up being kind of a triumph anyway: the oval piston engine.
That engine was fitted to one of Honda’s most unsuccessful race bikes ever, the NR500, a bike that represented Honda’s ambition to displace two-stroke bikes as the darlings of Motorcycle GP with a four-stroke bike.
At the time, Honda’s motorcycle racing rivals were using two-stroke bikes that made a lot of horsepower, around 120 HP, but Soichiro Honda famously disliked them, comparing them to bamboo contraptions. So, Honda engineers came up with a four-stroke bike with an engine that had oval pistons, as the company describes
Honda has detailed articles about the development of this engine in its archives, which are worth a read. One of my favorite bits in there is from Toshimitsu Yoshimura, who designed the engine. The engineer said, “When I look back at it, I’m not sure if we were experimenting with cutting-edge technologies or obsessed with foolish ideas.”
I think it’s fair to say that Yoshimura was right on both counts. The engine was both cutting-edge and foolish, but it’s still fascinating and the engineers had wildly ambitious hopes for the oval piston engine’s output. Maybe a little too ambitious, if the figures from Honda below are any indication