Soichiro Honda was a man of conviction. When the FIM announced in 1968 that the 500 cc engine class was limited to four cylinders, that gave a significant advantage to teams utilizing two-stroke engines. Honda made it clear that he was committed to the cleaner burning four-stroke engines. This forced Honda's hand. They withdrew from motorcycle racing to focus more attention on the automotive side of the business.
Two-strokes continued to dominate Grand Prix motorcycle racing into the late 70s, but Honda was convinced they could develop a high tech four-stroke race bike solution. In April 1978, after a nearly 12 year hiatus, Honda announced publicly it would return to Grand Prix motorcycle racing, specifically utilizing a four-stroke. Their return was marked with the NR500 - the oval-piston racing bike.