Vintage Motorcycles: Engine Evolution

November 24, 2016

Engines of vintage motorcycles have technology with ancient roots, but they also have a lot in common with modern engines. Learn more about the development of engines from vintage motorcycles to modern motorcycles.

Modern Motorcycle Marvels

One can often marvel at the high technology represented by a modern, state-of-the-art motorcycle motor. Every parameter of these fuel-efficient power plants is computer-controlled; depending on riding conditions you can choose between several control maps, effectively meaning that you have several motors in one; tolerances between moving parts, such as pistons and cylinder liners, for example, are thinner than a human hair; clutches and gearboxes are electronically controlled…

Origins of Technology in Vintage Motorcycles

But if you pause to think while you ogle manufacturers’ latest offerings at bike shows like Italy’s EICMA, you’ll soon realise that most of the technology shoehorned between a bike’s frame rails is pretty old hat stuff that was present on vintage motorcyles. The motor’s most basic parts, like pistons, conrods, crankshafts and cylinders, date back to the beginning of the Industrial Revolution in 18th-century Britain if not further: the Romans were already familiar with conrods and crankshafts, as was the Arabian mathematician, engineer and inventor Ismail al-Jazari (1136-1206), renowned for his fabulous work The Book of Knowledge of Ingenious Mechanical Devices; in fact al-Jazari can even be credited with the invention of the camshaft.

Reitwagen from Daimler Vintage Motorcycles in museum

Daimler Vintage Motorcycles: Reitwagen

The Very First Vintage Motorcycles

Back to vintage motorcycles, though. The first powered two-wheeler, called the Reitwagen, was created back in 1885 by Gottlieb Daimler and Wilhelm Maybach, although it’s pretty clear from looking at it that this was more of a testbed made to demonstrate that a vehicle could be powered by an internal combustion engine – I doubt anybody would last more than a few hundred metres on that uncomfortable-looking saddle!

line drawing diagram of 1894 Hildebrand Wolfmuller Vintage Motorcycles

1894 Hildebrand Wolfmuller Vintage Motorcycles Diagram

But a few years later in 1894, the first motorcycle (“Motorrad”) was introduced by Hildebrand & Wolfmüller. Although their design was quickly superseded by other manufacturers, on paper their engine design sounds rather modern – nothing less than a water-cooled, four-stroke twin. In reality, though, this engine was closer to a steam engine in its conception and the conrods worked directly on the rear wheel; with no clutch or gearbox, this must have made for a pretty hair-raising ride, particularly when getting underway from a standing start!

Hildebrand Wolfmuller Motorrad Vintage Motorcycles

Hildebrand Wolfmuller Motorrad Vintage Motorcycles

Early Engines in Vintage Motorcycles: Gearboxes But No Oil Pumps

The engines used by other manufacturers of vintage motorcycles were more conventional, even if still rudimentary: they didn’t have oil pumps, which meant that every few miles the intrepid motor-bicyclist had to manually pump oil round the engine’s lubrication circuit using a pump placed on the tank, often looking like an oversized steampunk syringe. They did, however, have rudimentary gearboxes, the most simple expression of which were a couple of different-sized front pulleys; one of these was for riding on flat terrain, and the other was for going up hills – the rider would have to stop at the bottom of the hill to manually switch the leather drive belt from one to the other, doing likewise once the ascent was completed.

Pretty soon, however, Sturmey-Archer developed the first iteration of the gearbox as we know it today, and by the end of 1920s, Velocette had introduced the positive-stop foot-change gearbox, which it fitted to the magnificent KTT. From that point forwards, the only notable development was the switch to unit construction, meaning that the gearbox was no longer a separate element (this, logically, is called pre-unit), but was instead housed within the engine’s crankcase.

Another technical that we take for granted today is liquid cooling. This was already in use in early motorcars, and it was just a matter of time before it was adapted to motorcycles. The most famous of the early water-cooled vintage motorcycles was the Scott Flying Squirrel, which can also be considered as the predecessor of the mid-80s Yamaha RD250 LC.

Multi-Cylinder Engines in Vintage Motorcycles

Although the first vintage motorcycles had small single-cylinder engines, manufacturers soon developed multi-cylinder engines, notably Henderson and Excelsior, who manufactured four-cylinder engines. Sorry, Mr Honda, you weren’t the first! The maximum expression of this was the 1950s Moto Guzzi V8 Grand Prix bike. Unfortunately, this exceptional machine never really had a chance to express itself since, by the time the engineers at Mandello del Lario had managed to get it working properly, technical regulations had changed and it was no longer permitted to race.

Henderson Multi-Cylinder Vintage Motorcycles

Henderson Multi-Cylinder Vintage Motorcycles

Engines in Modern Motorcycles

Nowadays, most medium- to large-capacity road motorcycles have a fuel-injected transverse four-cylinder engine, although many manufacturers still offer singles, twins, v-twins, v-fours and even inline triples. For example, here at the Black Douglas Motorcycle Co. we use 125cc and 250cc single-cylinder engines based on Honda’s CG 125 engine.

Not only does it look sufficiently “retro” for the vintage design of the Sterling Countryman Deluxe (it even has a kickstarter as well as an electric starter), but it is also very easy to work on – even for somebody with only basic mechanical skills – but it is pretty much bombproof, since it was originally designed for markets where it would be used as a workhorse and rarely see the inside of a workshop. It is also quite a lively performer, particularly in its 250cc version, giving the rider the real feel of the original vintage motorcycles. On a relatively light bike like the Sterling it gives outstanding fuel mileage despite the fairly small size of the petrol tank.

Other engine configurations do exist, but never really found success, such as the rotary (or Wankel) engine, which was used by Norton and Suzuki; indeed the development of road and race bikes fitted with rotary engines proved to be the downfall of the legendary British marque, since they were vastly expensive to develop, were prone to technical issues mainly concerning the lubrication of the rotor tips, as well as guzzling down fuel at a pretty alarming rate. Nowadays, Wankel-powered Norton Interpols and F1s, along with Suzuki RE-5s, are very sought-after by collectors.

Fuel Injection, Turbo, and Superchargers

In the 1980s, fuel injection, which had originally developed for aircraft engines before later being adapted to cars, first appeared on Kawasakis, before being gradually adopted by all manufacturers. The advantages of fuel injection are better fuel consumption – the control unit calculates exactly how much air-fuel mixture is required by each cylinder – and less pollution, since the injectors shoot a jet of vaporised fuel directly into the inlet port, thus optimising the fuel burn. Another development of that decade was the turbocharged motorcycle. However, this didn’t really catch on, and motorcycles such as Kawasaki’s GPz 750R Turbo and Honda’s CX 500 and 650 Turbo are seen as a period curiosity, a bit like large shoulder pads.

That said, Kawasaki recently developed the H2, which uses a supercharger rather than a turbo. Although supercharging (another thing inherited from aviation) was once popular in race machines of the Thirties, it’s not clear if this bike is just a demonstration of what Kawasaki can do in terms of making a hugely fast road bike, or if this a technology that will catch on in years to come.

The Future of Motorcycles: Electric Engines

And what about the future? Well, it’s pretty obvious that the future belongs to electric motors. I’ve already ridden an electric motorcycle, albeit a prototype machine that’s not yet fully ready for production, and I can assure you that it was a great experience: electric motors give you maximum torque right from the off, without having to get to a given rev range, which ensures very quick acceleration; and there is definitely something magical about riding along with just the sound of the air rushing over your crash helmet. In fact, here at the Black Douglas Motorcycle Co., we’d love to build an electric version of the Sterling one day; it would be wonderful to combine the elegance and beauty of early vintage motorcycles with environmentally-friendly electric engine technology. Watch this space, as the saying goes…

Marc Michon for The Black Douglas Motorcycle Co.