YAMAHA RD250

Yamaha’s first foray into the world of two-stroke twins, the YD-1, used a design, erm, ‘borrowed’ shall we say, from the German company Adler and their MB250. That first Yamaha 250 two-stroke twin was launched in 1957, but by then Adler had begun moving on to make office equipment instead of motorcycles and probably didn’t care. Yamaha’s early naming system seems to lack any logic, being a cluster of letters and numbers, with the smaller the bike the bigger the number, except when it isn’t. The big change came with the RD250 (common legend states RD was for Race Developed), which was officially launched in December 1972 but did not arrive in the UK until 1974.

The Yamaha RD250A was the first production road bike to use reed valves to control the fuel being guzzled at a considerable rate, giving rise to the ‘torque induction’ stickers on the side panels of the second wave of models. The principle behind the system improved usable mid-range power without compromising overall performance. The very first home and US market RD250s came with a twinleading shoe drum front brake, inherited from the YDS-7, but European models were equipped from the start with a rather good, if vulnerable to road dirt, twin-piston caliper front disc. The engine’s bottom end was practically identical to the YDS-7, as was the frame, which had some minor changes around the upper frame rails. Early production models were supplied with what were five-speed gearboxes; which were swiftly replaced with a six-speed box.