Why a joint venture with Honda instead of just importing Honda motorcycles to Taiwan from Japan? There are two answers to this:
1. Duties and taxes on imported goods were extremely high in those days. The government wanted to encourage local production, and so in many cases (for example, automobiles), the duty on imported goods could be as high as 180% of the retail price. Manufacturing motorcycles domestically avoided such added costs.
2. In the early days of the Republic of China on Taiwan, relations with Japan were not particularly sanguine. Japan had occupied and ruled Taiwan - a province of China - for 50 years leading up to World War II. When the war ended and Taiwan was returned to China, there was for many years a general anti-Japanese sentiment that discouraged the entry of Japanese brand products into the Taiwan market. However, domestic companies in Taiwan were not prohibited from assembling what were essentially Honda vehicles locally, as long as they did not carry the "Honda" brand name. The intense demand for motorcycles in the rapidly-developing Taiwan consumer economy of the early 1960's could not be met by purely domestic sources - so, there was no other option than to allow Sanyang Industry (SYM) to form a joint venture with Honda to manufacture the Honda Cub (re-branded the "WoWOW", of course) and other Honda models.