The engine is fitted into a genuine RD56 chassis (as per AMA rules) and the seat and tank are used as well from the same machine. Cylinders had chrome bores (as the TD1's). As the AMA rules permitted only 4 gears (because of the ancient Harleys of course.....!), the first gear was blocked off and a new topgear was designed. Topgearing was 142 mph at 9.500 rpm (227 km/h). The 2 machines ran with the standard Yamaha Autolube lubrication.

Yamaha Z608 350 racer 1967

These were also the first bikes with (experimental) electronic ignition. Performance was given as 45 hp