The Yamaha RD 350: Returns With 347cc of Raw Power Produced at 39 bhp at 7,500 rpm

The Yamaha RD350 is a legendary motorcycle that holds a special place in the hearts of enthusiasts. Originally produced from 1973 to 1975, it quickly gained a reputation for its performance and thrilling two-stroke engine. The RD350 wasn’t just a mode of transportation; it was an experience, offering a raw and unfiltered connection between rider and machine. Its impact on the motorcycle world is undeniable, and its legacy continues to resonate with riders of all ages.

The RD350’s popularity stemmed from its potent two-stroke engine, which delivered impressive power for its displacement. This, combined with its relatively light weight and nimble handling, made it a favorite amongsport bike riders. The RD350 was also known for its affordability, making it accessible to a wide range of riders. Its simple design and ease of maintenance further contributed to its appeal. The RD350 was more than just a motorcycle; it was a symbol of freedom and excitement.

While the original RD350 was only in production for a few years, its impact was long-lasting. The RD350 became a sought-after classic, with well-maintained examples commanding premium prices. Its influence can be seen in subsequent Yamaha models, as well as in the broader motorcycle industry. The RD350 remains an icon, a testament to the enduring appeal of simple, fun, and engaging motorcycles.

Yamaha RD350

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Evolution from Yamaha’s Previous Models

The RD350 evolved directly from the Yamaha 350 cc “R5,” inheriting its basic engine architecture but incorporating several key improvements. The most significant of these was the adoption of reed valves, which enhanced intake efficiency and boosted power.

The RD350 also benefited from a refined chassis and improved brakes, making it a more capable and well-rounded machine than its predecessor. The RD350’s development can be traced back to the Yamaha YR5, launched in 1970, which itself was a descendant of the YR1, Yamaha’s first 347cc model.

The engine’s cylinder dimensions and 180-degree crankshaft arrangement remained consistent throughout these models. The RD350’s main engine-related innovation was its reed-valve intake system, called Torque Induction by Yamaha. The reed valves, one located between each Mikuni carburettor and its cylinder, improved intake efficiency by reducing the amount of mixture that was spat back.

Engine and Performance Specs of the RD350

The Yamaha RD350 is powered by a 347cc, air-cooled, two-stroke, parallel-twin engine. With a bore and stroke of 64mm x 54mm and a compression ratio of 6.6:1, this engine produced around 39 bhp (29 kW) at 7,500 rpm, which was considered very fast for its time. The engine featured a reed valve intake system, which improved intake efficiency and contributed to its strong performance.

The RD350’s engine was known for its responsiveness and willingness to rev. Its power delivery was characterized by a strong surge in the mid-range, providing thrilling acceleration. The engine’s simplicity and relatively low cost made it popular among riders and tuners alike. However, the two-stroke design also meant that it produced more emissions than four-stroke engines, contributing to its eventual demise.

Frame and Chassis of the Yamaha RD350

The frame dimensions of the street 350 are very similar to the Yamaha TZ 250 and TZ 350 series factory road race bikes, differing mainly in weight and front fork rake. The RD being ~27 degrees and the TZ being ~25 degrees. The frames appear similar, side by side, with the street frame adorned with many brackets for the street equipment.

The weight difference is substantial though, with the street-going RD frame weighing almost twice as much as the “TZ” roadrace race frame. The RD350’s chassis was designed to provide a balance of stability and agility. Its relatively short wheelbase and responsive steering made it easy to handle in corners.

The suspension, consisting of a telescopic front fork and dual rear shocks, offered a comfortable ride while providing adequate control. The RD350’s braking system, featuring a single front disc brake and a rear drum brake, was considered to be the best in its class at the time.

Yamaha RD350’s Autolube System

All models were equipped with “Autolube” automatic oil injection, relieving the user from the need to mix gasoline and two-stroke oil. The Yamaha RD350 featured an “Autolube” system, which automatically mixed oil with the fuel. This eliminated the need for riders to manually mix oil and gasoline, making the RD350 more convenient and user-friendly.

The Autolube system injected oil directly into the intake manifold, ensuring proper lubrication of the engine’s internal components. The Autolube system was a significant innovation at the time, as it simplified the ownership experience and reduced the risk of engine damage due to improper oil mixture.

The system used a separate oil tank and a pump to deliver the correct amount of oil based on engine speed and throttle position. This ensured optimal lubrication under various riding conditions.

RD350: A Closer Look at the Brakes, Wheels, and Other Features

The RD350 came standard with a single front disc brake and a rear drum brake. Cycle Magazine described the combination as the best in its class. Rim sizes are 18″ WM2 (1.85″) front and 18″ WM3 (2.15″) rear, both being of chromed, wire spoked steel construction. In the UK, rim sizes were 1.60 front and 1.85 rear.Other notable features of the RD350 included:

• A six-speed transmission (five-speed in some markets)
• A comfortable seat and riding position
• A stylish design with chrome accents
• A reliable electrical system

The Yamaha RD350’s Lasting Impact and Legacy

The RD350 is infamous in the US. When the bike came out in the US, people famously remarked it to be the revenge of the Japanese on the US. The Yamaha RD350 quickly gained a reputation for its performance and handling. It became a popular choice for sport riding and racing, and its success helped to establish Yamaha as a major player in the motorcycle market.

The RD350’s impact extended beyond the racetrack, as it also influenced the design of other motorcycles. The RD350’s legacy is evident in the numerous fan clubs and online communities dedicated to the model. Its enduring popularity is a testament to its timeless design and thrilling riding experience. The RD350 remains a sought-after classic, with well-maintained examples commanding premium prices.

Its influence can be seen in subsequent Yamaha models, as well as in the broader motorcycle industry.

Rajdoot Yamaha RD 350 (HT)

The ports on the engine needed a fair deal of work before they matched/ beat them—one of the reasons why the US specification barrels became a sought-after modification.If you’re getting US Spec barrels, it would be wise to invest in good pistons (and other 3rd party parts) from brands like Wiseco.

Look around on the internet for deals or offers. Someone had mailed me questions about how to go about porting their barrels. If you’re someone like that, leave the engine modification to someone who knows his job. RD barrels are hard to come by, and don’t waste the ones still around.

Technical Specifications

Gear Ratios

Power transmission

Dimensions

Braking system

Filling Capacity

Tyres

Generator

Rajdoot Yamaha RD 350 (HT) Lights

Frame

Transmission Oil

Suspension

Rajdoot Yamaha RD 350 Engine

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RD350

The RD350 was truly a motorcycle ahead of its time. The bike came with a lot of things that were new to the Indian motoring scene. The RD was equipped with Yamaha’s Torque Induction technology.

Torque Induction ignition system in a two-stroke engine uses a reed valve (check valve) which allows charge (air+fuel mixture) to go only in one direction i.e. to the combustion chamber. If there is no reed valve, the mixture in the combustion chamber tends to flow back down to the crankcase during a low-pressure situation (when the piston moves up).

The result of Torque Induction was high low-end torque without compromising much of top-end power.