Here are the two first paragraphs translated as good as my daughter Rachelle can work out.
1. At that time, the Ueno Bike Parts Shop sold RZ parts in great numbers. It was said Itoushi (maybe a person or company??) intended only one way given out?? The original Yamaha logo is white with an outline. 2. In the fuel tanks sold later on, the Yamaha logo was changed to gold. That is, the white outlined with black letters used in the original tank design were replaced with gold lettered Yamaha logo which was the product of an error.
So now you know. A later batch of two stripe tanks had the wrong logo fitted in error! :-)
"Every day spent above ground is good. Every day spent on two wheels is better."