Hamamatsu, Japan — When Yamaha first decided to hire women for its motorcycle assembly lines, male workers strongly objected.
''They work piece rates and were convinced women would slow down production, '' a company spokesman recalls.
It has not worked out that way.
''They're a bit slow in learning at first, but eventually become capable of working faster, producing better quality than men,'' says assembly line supervisor Motoo Makimura.
Yamaha today has about 3,000 women (about half the work force) on the assembly lines of its Iwata plant in central Japan, which turns out a motorcycle on average every 3.5 seconds.
Most work alongside men for virtually equal pay.
But the company has found that women actually do their best work when separated from men.
As a result, an all-female assembly line was established in 1976. There are 45 women working on the engines, and 65 on frame assembly.
Last year they produced a record 485,000 machines. This year they're aiming to top half a million.
In the mid-1970s, the internationally famed company decided to develop a range of lightweight 50-cc motorcycles just for women.
It was company president Hisao Koike's idea that they should be made by female workers ''because they have a more delicate touch and a better feel for the type of machine their sisters would like to ride.''
Young women are recruited on graduation from high school. They are given a week's basic training in quality control, safety, and production costs before they join the assembly lines to begin with simple jobs like tightening nuts and bolts.
Mr. Makimura, who has been in charge of the female line for four years, says: ''Some of the senior girls can easily do their own maintenance and could start their own motorcycle business. The idea that women are not mechanically minded is simply male egotism.
''I think an all-girl assembly line was a necessary step because once you give them some sense of responsibility they do a much better job than men.''
''It doesn't work as well if men and women are mixed together on the production line,'' adds Kayoko Makita, who is one of four group leaders on the line.
Maybe it is because Japanese women have been conditioned for centuries to defer to the male and to boost his ego by a pretense of being totally helpless.
Whatever the reason, Mrs. Makita says, ''The fact remains that, if women are placed alongside men, they tend to rely on their male colleagues too much. They won't take any responsibility or try to be self-reliant.
''On their own assembly line, however, the girls develop a confidence in their own abilities. They handle problems when they arise, rather than looking around for the nearest male.''
Some differences between the sexes emerge in their approach to suggestions for improving the company.
Explains Mr. Makimura: ''The men look beyond their immediate surroundings to ideas directly related to a better product. The girls concentrate on ways of improving their surroundings, the working environment, and making their job easier.''
Yamaha built a special assembly line for the all-woman operation. It designed special tools--for example, a wrench operated by compressed air--and installed more robots to eliminate any heavy jobs.
The two lines in Plant 7 that are the female preserve have a very unfactory-like atmosphere. Vases of flowers brighten the area. The women (average age 22) wear brightly colored aprons adorned with English slogans.
Alongside the line, a display board is covered with drawings of nudes. This is actually the women's own idea, part of a company incentive plan.
''They wanted something a bit more interesting than the usual dull graphs and charts you see in factories,'' explains group leader Makita.
The nudes are covered from neck to ankle in six stages. Each time a woman's suggestion is accepted by the company, she colors in one section of the figure. When the figure is fully clothed, she can qualify for a bonus of up to $500.