Although there are inevitable similarities between the RD400 and 350 that preceded it, the two-stroke 40bhp has developed enough to make it bigger, softer, quieter, faster and longer lived. Yamaha improving stroke 51cc engine to add to the capacity of the machine, which requires new crankcases, and the newly installed barrel and cylinder head. Engine breathing through a new airbox arrangement, and the motor is rubber-mounted in a frame. These days, it seems an RD is not complete without a [...]