Yamaha RD 400

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RD 400, model 1A3, manufactured in 1977

The Yamaha RD 400 is like the Yamaha RD250 a two-stroke motorcycle the Japanese motorcycle manufacturer Yamaha .

The RD 400 model came onto the market in 1976 (internal designation 1A3) as a replacement for the very narrow air-cooled predecessor model RD 350 in terms of performance . For the first time in mass production, there was a disc brake on both wheels. In 1978 there was a modernization with contactless transistor ignition , a revised footrest system (the previously existing footrest bracket ran below the muffler and made for tricky situations in bends with undulating road surface when driving hard) and a new design. The internal designation was 2R9. For both versions, there were still thicker cylinder head gaskets, as the models equipped with contact ignition in particular tended to use the notorious “money box” (burning through of the piston crown) if the pre-ignition setting was neglected. The 2R9 version was only produced for a short time, as the water-cooled versions of the RD models were delivered to the European market as early as 1980 , thus finally ending the era of air-cooled two-stroke engines in the Yamaha model range.

Strengths and weaknesses

The trade press and test reports revealed chassis weaknesses: The rear wheel swing arm was mounted in plastic bushings, which worn out prematurely, triggered axial play in the bearings and led to chassis unrest (oscillation). A conversion to bronze bushes or tapered roller bearings was recommended, so-called "box swings" were also offered by the accessories trade; This was the name given to swing arms whose arms were made in a "box profile" instead of round tube profiles, which should result in greater torsional rigidity.

Technical specifications

Surname model Construction period power Displacement Front brake rear brake rims
RD 400 1A3 1976/1977 43 hp 397 cc Disc 267 mm, fixed caliper Disc 267 mm, fixed caliper Cast aluminum
RD 400 2R9 1978/1979 43 hp 397 cc Disc 267 mm, floating saddle Disc 267 mm, floating saddle Cast aluminum, relieved