Picture this: It’s the late 1970s, and you’re a Honda engineer working for the man himself, Soichiro Honda. It is a truth, universally acknowledged, that the Old Man absolutely, unequivocally hates two-strokes. However, he loves testing his company’s engineering mettle in motorcycle racing—and also, it's the time when two-strokes rule the world. Additionally, there's that teensy conundrum that most racing series tend to have: A set of rules that must be followed. What do you do?
If you’re Honda, you get to work engineering a new four-stroke, four-cylinder machine. According to the existing rule book, four is the maximum number of cylinders a bike can have, 500cc is the max displacement, and the bike must also be naturally aspirated. With two-strokes of the era hovering around the 120-horsepower mark, it’s certainly a difficult puzzle to work out—but impossible?
Not if you’re completely out of your mind—er, if you’re Honda, we mean. (We kid. Around here, the general consensus is that weird Honda trying new things is best Honda, and we’ll certainly take interesting failures over boring also-rans any day of the week.) If you’re familiar with Honda’s oval-piston bikes, the NR 500 and the later roadgoing NR 750, that problem is exactly what Honda’s engineers were trying to address. (The NR designation, in typical understated Honda fashion, stands for “New Racing.”)
To get a four-stroke, four-cylinder engine to make the kind of power that the two-stroke competition was generating with ease, Honda had to think differently. Increased airflow was a must, so the engineers started thinking about the valves. If you could get more airflow, more combustion, and higher revs, that engine could theoretically generate the kind of power needed. That’s how Honda’s engineers came up with a design involving eight valves per cylinder.
Naturally, those eight valves all need room to operate, which is how the piston came to be oval-shaped. Furthermore, the new piston design and high revs expected required two connecting rods per piston, as well—not to mention a complete rethink of the piston ring design. To make a long, incredibly weird story short, each problem Honda tackled seemed to lead to a number of other problems, all of which the team also had to tackle if it was going to successfully create its newest racing powerplant.
The result of all this hard work was the NR 500, which Honda finally ended up racing in 1979. Unfortunately for the team, it didn’t perform as well as they’d hoped, only managing to eke out two race wins the entire season. Honda shelved the idea until 1992, when it was decided that the time was right for a production oval-piston bike. That’s how the NR 750 came to be—but at an MSRP of roughly $60,000, it’s probably not that difficult to understand why it didn’t exactly fly out of showrooms. Still, Honda's unique approach to problem-solving has historically yielded some of its best-loved bikes.
Sometimes, simple is best—but sometimes, taking the winding, complicated route to answer a question is a whole lot more interesting. Thanks for giving us something to think about, Honda.