Extreme Machines.

Rim sizes were 18" WM2 (1.85") front and 18" WM3 (2.15"), both being of chromed, wire spoked steel construction. In the UK, rim sizes were 1.60 front and 1.85 rear.
Brakes were: single front disc brake and a rear drum brake, which Cycle Magazine described the combination as the best in its class.
The frame dimensions of the street 350 were very similar to the famous Yamaha TZ250 and TZ350 series factory road race bikes, differing mainly in weight and front fork rake - the RD being ~27 degrees and the TZ being ~25 degrees. The frames appeared similar, side by side, with the street frame adorned with many brackets for the street equipment. The weight difference was substantial though, with the street going RD frame weighing almost twice as much as the "TZ" roadrace race frame.
The stock bike made about 32 to 35 true rear-wheel HP at about 7500 rpm - very fast for the time. A contemporary of the RD was the Kawasaki H2 750cc Triple, said to make 72 to 75 true HP (tested by Cycle Magazine at 55bhp).
The 350 evolved into the more refined and cleaner running RD400C in 1976, the "D" and "E" in 77-78 and the final model, the white 1979 RD400F.


The bike was a very snappy performer and was popular with beginner riders. However, the combination of a stiff suspension, relatively abrupt power delivery and very powerful brakes to the inexperienced riders led it to being regarded as being "too fast" for new riders (uncontrollable 1st gear wheelies in the hands of careless riders were not an uncommon problem). Its good performance, light weight, and easy maintenance made it a world favorite but it ultimately suffered at the hands of increasingly stringent noise and tighter emissions standards in the US market and changing consumer appeal.
Its also worth noting that the Yamaha RD was the UK's second most stolen vehicle in 1982, the first being a Ford Cortina.