The Concept: An OHV + Inclined Cylinder that Changed the World of General Purpose Engines
The OHV configuration, while it offered key advantages, also necessitated more parts, a problem that was eventually solved through an exhaustive program of integration. For example, the fuel cock located between the fuel tank and carburetor serves the purpose of preventing fuel leaks during transportation and overhauling. With the ZE engine, the need for a separate fuel cock was eliminated through integration with the carburetor. Adopting the bonding technique of caulking three plates allowed the fuel tank to be mounted directly on the head, further contributing to a reduction in parts. As a result, the number of parts in the new OHV engine, which a normal design would have increased by about 20 percent, was reduced to a number even lower than found in the ME engine.
A key point in the reduction of parts, in addition to the effective ideas incorporated through new mechanisms, was that the development team had achieved such a thorough understanding of the ways general-purpose engines were used. They not only consolidated the parts from an engineering perspective, but also distinguished the necessary parts from unnecessary ones based on product usage. Their experience in field-testing had been put to maximum use. The 20 percent reduction in parts had undoubtedly led to a drop in cost, but more importantly doing so did not sacrifice the functionality of the engine. This was a real advantage for the ZE engine.
Various ideas had been adopted in order to make the OHV engine easier to handle, one such innovation being the mechanical decompression mechanism. An OHV engine offers a better compression ratio due to higher fuel-combustion efficiency. However, this leads to higher pressure, so greater force is required to start the engine. Therefore, a decompression mechanism was added in order to reduce the starting pressure. During the mechanism's development several different ideas were attempted and abandoned, since it was essential that the team avoid any patent infringements. Their effort finally led to the establishment of a proprietary Honda technology.