RD400 1978 USA
Although there's an inevitable family resemblance between the RD400 and the 350 which preceded it, the 40bhp two-stroke had been considerably developed to make it bigger, smoother, quieter, faster and longer-lived. Yamaha increased the engine stroke to add 51cc to the engine capacity, which demanded new crankcases, and fitted new barrels and cylinder head. The engine breathed through a new air-box arrangement, and the motor was rubber-mounted in its frame.
The last of the fast but potentially fragile two stroke sports machinery from Yamaha, was a joy to ride, and seriously faster than any other 400 of that period, four BHP up on the much more expensive Honda CB400F for example, and a genuine 100MPH machine, with a standing quarter time of around 14 seconds.
When launched in 1976 the British publication “Motorcycle Mechanics” had this to say:
'It's a well finished sports bike with all the traditional Yamaha performance and better flexibility. By many standards the fuel consumption isn't good but it's a whole lot better than it might have been.'