Anyone who was old enough to ride a motorcycle in the 1970s will remember the fanfare that greeted the launch of the original Yamaha SR models. Inspired by the dual purpose XT500 which was launched a few years earlier, the single cylinder SR400 and SR500 were announced in 1978, and went on to become some of Yamaha’s most popular and enduring models.
With their relaxed torque output, slim and agile chassis design and classic styling, the Japanese-market SR400 and European-market SR500 became firm favourites with enthusiasts who were looking for a simple machine that captured the very spirit of sports motorcycling. In many European countries including Germany, Austria and Belgium, groups of SR500 owners formed enthusiasts’ clubs, many of which still run to this day. To underline its appeal, the SR500 went on to win consecutive ‘Moto of the Year’ awards from Germany’s Motorrad magazine – one of the highest circulation motorcycle titles in Europe. During the same period the bike was establishing a cult following in Europe and Japan, with many SR models being handed down from father to son.
Enduring appeal since 1978
Meanwhile, in Japan, legislation relating to the motorcycle licensing system in the mid 1970s had created demand for 400cc models, and so the SR400 became a top seller in its home market. Virtually identical to the SR500 but running with a shorter stroke to achieve a capacity of 400cc, the SR400 has continued to attract massive interest in Japan over the last 35 years, with thousands of owners and enthusiasts turning up to SR rallies throughout the country.
What is also interesting is that more than half of the owners of the SR400 in Japan are younger than the bike they ride! Users born after 1978 now make up the majority of owners in Japan, which demonstrates clearly that this timeless motorcycle has an enduring appeal with the newer generation of riders.
The return of a legend
For 2014 the return of the SR will spearhead Yamaha’s growing Sport Heritage line up, which offers today’s riders the opportunity to experience the joy and pleasure associated with simpler and more traditional designs.
Yamaha’s classic big single has a genuine heritage and pureness of design that sets it apart from some other ‘retro’ models. There can be no doubt that the SR400 is the real thing, and with an authentic engine and chassis specification and original kick start mechanism, this charismatic twin-shock thumper is aimed at the many riders who are looking to rediscover the very soul of motorcycling.
For many riders, the character, soul and image of a machine is far more important than its 0-100km/h acceleration figures or potential lean angle. Having been brought up with the ready availability of high performance motorcycles all around them, an increasing number of today’s riders have decided that what matters to them are the fundamental qualities such as simplicity, ease of use and timeless design. With its relaxed torque, light and agile chassis and sheer mechanical beauty, the SR400 is designed to appeal to those riders who are looking for a motorcycle with a real heritage and character, and one which fully engages its owner.
In addition to its appealing character and easy performance, the SR400 also offers many possibilities for those riders who want to customize their machine, whether that involves adding a few bolt-on parts or going the whole way and creating a café racer, street scrambler or bobber.
By offering a return to the fundamental values of biking, and instilling a new pride of ownership with the rider, the SR400 is ready to make friends with a whole new generation of owners that were born after the bike made its original debut some 35 years ago.
Ideal for customization
The interest in customization is growing, and many of today's riders are looking to create their own unique motorcycle by using special parts. With its twin shock chassis and single cylinder air-cooled engine, the SR400 is the ideal starting point for any customization project.
With its simple design, this timeless motorcycle can be transformed into a café racer, bobber or street scrambler, allowing the owner to create his or her own unique special.
Air-cooled 4-stroke single-cylinder engine
With its pulsing power delivery, throbbing exhaust note, strong physical presence and mechanical simplicity, the big single holds a special place in the hearts of motorcyclists all over the world.
At the very soul of the SR400 is an air-cooled 4-stroke single cylinder SOHC 2-valve engine which is technically almost identical to the original design, with a few exceptions.
The SR400 runs with a bore x stroke of 87mm x 62.7mm and a compression ratio of 8.5:1, and this well proven formula gives an excellent torque output that allows the SR400 rider to accelerate strongly from low revs without having to downshift. Also contributing to the SR’s healthy torque output is a large-capacity air cleaner, as well as a big 47mm intake valve and optimized flywheel mass, which work together to give the SR400 an effortless and relaxed running character.
Fuel injection for easy starting and good economy
The major difference between the original engine and the reborn powerplant is the use of a new fuel injection system, which allows the bike to conform with current emissions regulations, and also makes the SR400 easier to start than the original model.
This compact and simple new fuel injection unit delivers smooth engine running in a variety of riding conditions, and it occupies the same space as the original carburettor to maintain the original looks of the engine. Another advantage of this new fuel injection system is that it ensures excellent fuel economy, allowing the rider to achieve optimum range from the 12-litre fuel tank.
Our engineers wanted to ensure that the 2014 model is true to its original character, and so the only way to start the new SR400 is to kick it! Riders who may have owned an original SR400 or SR500 will remember that kickstarting the older models required something of a special technique which could take some time to master.
However, the good news for the new generation of SR400 owners – and also for older riders who may be returning to this Yamaha big single – is that the new fuel injection system ensures much easier starting. The bike now runs with a newly designed transistor ignition system that generates a better spark which also helps when starting the bike up. An indicator on the right side of the cylinder head shows when the piston is in the best position for starting, and a decompressor lever on the left side of the handlebars supports the rider in starting the engine smoothly.
Beautifully finished air-cooled engine
As well as its relaxed and easy torque delivery, another everlasting attraction of this engine is its sheer mechanical beauty. With its large air-cooling fins, shiny crankcases and gracefully curving exhaust pipe, this big single is a classic design in every sense of the word. In an era when many engines are hidden behind fairings, the sight of the SR400’s big air-cooled engine is a joy to behold.
To prevent discolouration of the big-bore exhaust pipe its exterior surface has been treated with a special nano-film coating, while the polished engine cases feature a clear-coated buff finish to maintain the gleaming looks of this classic powerplant.
3-way catalyser with oxygen sensor
Hidden inside the SR400’s chrome plated muffler is a 3-way honeycomb-type catalyser coated with platinum and other precious metals, and this system – together with the new fuel injection system – allows the air-cooled single cylinder engine to exceed current EU emissions regulations.
Engine Technical Highlights
Tubular high tensile steel semi-double cradle frame
Staying absolutely true to the original layout, the 2014 SR400 is equipped with a compact and slimline semi-double cradle frame which perfectly complements the character of the single-cylinder engine. This proven design is manufactured from tubular high tensile steel that offers the optimum balance of strength, rigidity and weight, giving an agile feel and easy handling character.
Oil in frame
The SR400’s frame has been designed to carry the engine oil which runs through the main downtube and into the engine, and this oil-in-frame design offers a number of advantages over a wet sump system. Pumping losses within the engine are reduced, and because there is no need for an oil sump beneath the engine, the SR400’s ground clearance is higher. This design also allows for a slimmer body, which gives plenty of potential options for riders who want to build their own custom bike.
Plush front and rear suspension systems
The SR400 is equipped with traditional upright front forks that give 150mm of wheel travel for a smooth ride and easy steering. At the rear end this classic big single is fitted with a proven twin shock system that offers 100mm of suspension movement. Together with the well-padded dual seat, the smooth action suspension ensures a relaxing ride, making the SR400 one of the most comfortable ways to get about in the city or countryside.
Classic 12-litre teardrop fuel tank
Throughout its long history, the SR400’s fuel tank design has remained largely unchanged, with the only real ‘update’ over the years being different paint and graphics. The SR400 is equipped with the same familiar teardrop style fuel tank which is virtually identical to the original design, with the exception that the 2014 tank offers a capacity of 12 litres.
The focal point of the graceful teardrop tank is Yamaha’s classic tuning fork logo, and the plain colour scheme is highlighted by a simple ribbon-type band that runs around the tank’s sides.
Front disc brake and rear drum
The SR comes with a drilled front disc which is slowed by a modern 2-pot caliper. Braking at the rear end is provided by a sealed drum brake, and this proven front disc/rear drum combination delivers smooth braking performance with plenty of feel.
Balance-type centre stand
It is anticipated that the SR400 will attract many owners who will want to carry out a variety of maintenance jobs themselves, such as routine inspections, customization projects and tyre changes. In order to facilitate this work in the garage at home, the SR400 is fitted with a balance-type centre stand which makes maintenance easier and more convenient.
Lightweight aluminium rims with 18-inch front and rear tyres
The latest reincarnation of the SR400 is equipped with 18-inch spoked front and rear wheels that perfectly match the character of this traditional big single. These stylish wheels are equipped with lightweight aluminium rims which ensure low unsprung weight for smooth suspension characteristics.
Chassis Technical Highlights