The RD400 is a 399 cc (24.3 cu in) two-stroke air cooled six-speed motorcycle produced by Yamaha from 1976 until 1979.

The RD series was discontinued in the USA due to new emissions rules in the early 80's (by which time the last model was the renamed RZ350 water cooled motorcycle).

Picking the cast wheel option gave a disc rear brake as well.

In Germany, these RD models came with spoked wire wheels AND front and rear brake discs.

[2] In 1978 the RD400E was fitted with a capacitor discharge electronic ignition (CDI) unit, as well as thinner spoked cast wheels, a new foot peg position, and some minor engine modifications with revisions to cylinder porting and carburettor specs.