The Yamaha RD Range of Motorcycles

RD 350 Yamaha, cafe racer style. John H Glimmerveen Licensed to About.com

The RD range of Yamaha's, 60, 100, 125, 250, 350 and 400 twins, can trace their ancestry back to the 1957 YD 250 racer. The twin cylinder, piston ported 2-strokes raced in the 60s helped to make Yamaha the household name it is today. In fact, the winningest race bike in history - the TZ Yamaha - can trace its history back to the early YDs.  

Racing was, and still is, always part of the marketing strategy for Yamaha.

Many of the technologies developed for the track found their way into the company's street bikes. It could be argued that some of these technologies were more gimmic than a practical improvement (anti-dive, for example).

Market Leaders

First introduced in 1972, the RD range of 2-stroke twins were developed for street use from the Grand prix racers of the 50s and 60s, firstly in air-cooled form, then later with water cooling (known as the RD LC range). From the 60s through to the early 80s, 2-stroke motorcycles from 50 to 750-cc were market leaders in volume sales. But as the world became conscious of the need to reduce emissions, the venerable 2-stroke manufacturers began to develop more 4-stroke machines. Primarily because the 2-stroke technology could never negate the engine's inherent problem of total loss  (through the combustion process) of its engine lubrication.

Today the RD range of Yamahas are becoming popular with collectors of classic bikes the world over.

They are fast, easy to work on and offer good performance, but are not good on emissions or fuel consumption. In addition, as so many of these machines have been produced, the parts availability is good, including competition and performance parts.

Reed Valve Induction

Early versions of the RD Yamahas relied on the simple piston ported 2-stroke engines.

In essence, the piston in these engines is a multifunctional unit controlling the inlet and exhaust phases and also transmitting power to the crankshaft. The layout of the RD engine was very similar to their racing counterparts, the TZs. Interestingly; the RDs used reed valve induction before the TZ racers of the time.

As with most 2-stoke motorcycles, the RD Yamahas can be tuned easily and respond particularly well to aftermarket exhaust systems based on the expansion chamber design. However, these aftermarket exhausts tend, in most cases, to narrow the power band making this bike less easy to ride.

Many owners also increased the compression by having their cylinder heads machined by specialist machine shops, and also added bigger carburetors.

Today, the RD Yamaha is often used as a basis for a café racer too. Although the Yamahas differ considerably to the Norton and Triton café racers of the era, they offer the same ease of tuning, performance and looks the original café racer owners sought.

Prices for a RD differ considerably, but as an example, a 1978 RD400E in excellent condition is valued around $8,000. However, the recorded mileage will make a big difference to the value of such a machine.

Plan on having the engine rebored with new pistons if the bike has covered more than 20,000 miles which most older machines will have done. 

Note: A lot of these machines have been used in production (stock) racing series'. When inspecting a bike, check for telltale signs such as the oil drain plug on the gearbox having a small hole for wiring purposes.