The Motorcycle That Gave Birth to the Nanahan Category
Saitama Factory (currently Wako Plant) and Hamamatsu Factory were in 1969 selected to produce the CB750 FOUR's engine and body, respectively. American Honda sent two engineers to Saitama Factory to join the staff for a series of tests, in which 300 items were checked from the user's perspective. Honda Motor had high expectations for the exportation of the CB750 FOUR which was believed to be a strategically important bike for increasing the sales of other Honda models on the U.S. market.
This was Honda's first attempt to market a big bike, and therefore it would be hard to forecast sales accurately. For that reason each plant decided to make effective use of idle production facilities, normally used for power products. This would serve to minimize the company's overall investment. Modifications and overhauling, however, would be needed before their equipment could be used to build the CB750.
Honda's previous models used a spilt-type, press-fit crankshaft having a needle bearing. However, the four-cylinder powerplant in the CB750 FOUR employed an integrated crankshaft and metal bearing. At Saitama Factory, the staff wracked their brains trying to identify the right machining equipment and line configuration to produce a part they had no experience making. They even visited automobile manufacturers in order to acquire some knowledge they could use to plan the line.
Efficiency on the line was poor initially, and as a result the production volume was at most five units per day. However, the machine became an instant smash hit, bringing tears of joy to everyone involved with the CB750's creation. The initial production forecast of 25 units per day was pushed up to over 100 units. Back orders piled up as a result of this explosive, yet completely unexpected sales activity. Soon, the production of sand-molded crankcases, for which the factory did not have a dedicated machine, could no longer meet the rate required for mass production. In response, the entire crankcase production facility was upgraded to adopt the metal die-cast type. The line was gradually enhanced as production volume increased. However, every time the volume was adjusted, additional employees would be mobilized to run a temporary line. Everything had to be accelerated in order to produce such a number of bikes at Honda's level of quality. Ultimately, though, the production of engines and bodies was transferred to Suzuka Factory - in July and October 1971, respectively - as part of the company's endeavor to satisfy customer demand.
Suzuka Factory was then building the CB500, using a production line within its automobile plant. However, there were problems with this facility, including a restrictively narrow corridor along the line that hindered the smooth flow of parts. Therefore, with the assumption of CB750 Four production, the factory took a long-term view and changed the L-shape line for body assembly to a straight-line configuration. The move offered a better work environment and vast improvements in employee safety.
The organizational structure and operator training were improved, too. To that end, a dedicated organization was formed for the production of the CB750 FOUR by gathering selected personnel from the Honda 1300 and TN lines. The resulting vacancies on those lines were then filled by personnel from the factory's auto plant. Those assigned to the motorcycle production line were then given orientation concerning the major differences from automobile production, particularly with regard to the prevention of damage to the product's exterior. Accordingly, the line started up on schedule, with all cost and quality objectives satisfied.