The Concept: An OHV + Inclined Cylinder that Changed the World of General Purpose Engines
Honda ordered the development of a consumer-oriented engine in October 1980 with the intention of having a successor to the popular ME model. When the decision was made, the ME's yearly sales volume was still under the 1 million mark, but it was only a matter of time before the figure would pass it. However, the ME engine had been developed for the industrial market, so in order to expand its overall market share for general purpose engines Honda had to gain a foothold in the consumer arena. To do this, the new engine's yearly sales target was to be three million units.
To develop a new engine that was small, economical and maintenance-free, Honda's development staff analyzed vast collections of data gathered from the many ME engine units that had found their way into the world. And with that analysis a research project was started with two possible directions, the first being a side-valve (SV) engine with smaller displacement but higher performance, and the second being an overhead valve (OHV) engine.
The oil crises of the 1970s had made society more conscious of the need to conserve energy resources, and through its ME experience Honda knew it had to find a decisive feature unavailable with competing engines. Accordingly, the research effort began to focus on a fuel-efficient, high-output OHV engine. In 1981, Honda officially decided to adopt the OHV design as the mainstay of its next-generation engine line. Research was specifically directed to identify a structure and concept suitable for lawnmowers and general purpose applications.
Honda's interest in lawn mowers reflected a desire to reach out to customers for power products in the U.S. With regard to lawnmowers, Honda's engines were already respected among professionals for their superior performance, even prior to the ME's introduction. However, to meet current expectations and build sales, the OHV configuration was absolutely necessary. Therefore, the ZE project began with a two-prong approach, aiming to develop the ZE01 general-purpose engine and the ZE5 for lawnmowers.