SY Motors Co., Ltd., Nagoya, 1946-49?
SY Motors still exists today under the name of Swai Automobile Company (エスワイ自動車) whose parent company is Seito Oil Co., Ltd. (西東石油株式会社), and they are listed in the Japanese language wikipedia site. They made at least one machine called the SY (SY号), but I have not found any information as to what they used as an engine type, or the displacement. On the company website is a very small photo of two of their machines, but that is the only image I have been able to locate. Also mentioned on the website is that in 1947 they won the 1st Shizuoka Prefecture Light Vehicle Race Tournament, however I have not been able to find any additional information that corroborates this.