In July 1959 the first pictures of the Yamaha YDS-1 appeared in the Japanese magazines.

It was still called the "250-S"

The YDS-1 Prototype differed in the following respects from the later production version:

1.  Paint: Blue fueltank, headlight, seat and mudguards/fenders; greyish frontfork, frame and toolbox.

2.  Chrome: fueltank and airfilters chrome, but not the chainguard.

3.  Rearlight: Different shape.

4.  Front mudguard/fender: additional stays above.

5.  Rear mudguard/fender: additional stays are from flat stamped material instead of tubing.

6.  Chainguard: different shape from production model.

The brochures are from 7/1959 (production start 7/59)