One cylinder: praise for simplicity
In the beginning, the motorcycle was single cylinder, simple and compact. Mounted on thin and light machines, it forged legend with BSA Gold Stars, Norton Manx ... and Yamaha 500 XT ... But over the years bikers asked more of their mounts and the mono took a dip.
Arms race
This KTM 450 cylinder head in itself demonstrates the compactness of a single cylinder and explains its lightness.
The natural evolution of modern motorcycles is moving towards more comfort, more speed, more reliability. Areas that are not the prerogative of mono. Indeed, unbalanced in nature and offering poor cyclical regularity, it hits hard at low revs, which earned it the nickname "Tuper" (a cogner in Shakespeare's language). In addition, in the search for performance, one cylinder slows down. It makes sense, because to increase power, you can either increase the displacement or the engine speed. In both cases, he admits his limitations. If the displacement increases, the piston gets larger, therefore heavier. In fact, the forces of inertia that cause wear and vibration increase at the same time. The same problem if we are trying to reach high speeds, because as inertial forces develop at the square of the speed, we face the same risks of breakage, wear and vibration…. Therefore, mono should be limited to medium forces, without being able to pretend to break records…. In fact, his last Grand Presidency victory was in 1969. It was Norton Mans, and the race was raining. Then the multi-cylinders, 2 and 4 strokes, finally replaced it.
After the war, English single top cylinders were the ultimate weapon of choice for private pilots who wanted to escape. However, they had to change frames in the late 1960s in the face of advances in two-stroke and multi-cylinder. Here's Matchless G 50: It was a competitor to Norton Manx. It featured a simple ACT engine.
Yamaha rethinks loudly
I'm legend. ACT one air cooled 2 valve engine, shock start and drum brakes. The 500 XT is the opposite of progress, but it will be a hit. It is to her that we must return the thunderous.
However, in 1976 Yamaha updated this technology, finding it a perfectly adapted environment: Cross Country Running. Combined, economical, full of character, the single cylinder is the worldwide success of the 500 XT. Competition followed suit very quickly, and the phenomenon took on unsuspected proportions with the development of the Paris Dakar. The single-cylinder trail then becomes a symbol of freedom, adventure and escape. We are at the dawn of the 1980s. But history stumbles when BMW races with its famous flat twin. Despite its efforts, increasing displacement, multiplying valves, double ACT, etc., the mono will not be able to withstand the multi-cylinder wave. Making way for the asphalt, he bows down to the sandy paths. Definitely dead? Of course not, the one cylinder is a rustic mechanism that can withstand abuse. Therefore, he will be reborn from his ashes, like the Phoenix.
The last bastion, the last battles
Return to Grace: The use of racing technology allowed the monos to return to strength and win both times in favor of bias equivalence. The TT remains the only place where Hi-Tech single cylinders are still available. Here is an upside-down Yamaha 450 twin ACT Yamaha XNUMX cylinder head and injection.
Now the only alternative is a clean and tough SUV. Here, weight and compactness are important qualities that transcend pure strength. It is impossible to walk a hundred or more horses through muddy terrain filled with bumps. It is also impossible to effectively deal with a machine weighing about 200 kg. There is no room for a multi-cylinder (yet). But until recently, a 4-stroke mono could not fight against a 2-stroke with equal displacement. But when tougher pollution control pushes push-pull to the exit (emphatically, history repeats itself again!), It imposes itself. In favor of the displacement equivalence of 125 2 bits / 250 4 strokes and 250 2 bits 450 4 strokes, we see the birth of a new breed of medium displacement single cylinders that are powerful, lightweight and efficient. This new generation of high-tech single cylinders cannot be counted. Double ACT, 4 titanium valves, liquid cooled, forged pistons ... They are well over 100 hp. and maintain a speed of about 13000 rpm at 250 !!!
This mutant breed is looking at the asphalt again thanks to supermodern fashion, with the sole ambition to reclaim this land. Mono hard!
Austrian manufacturer KTM remains the hottest single-cylinder defender on the road. The performance and reliability of its 690 is breathtaking for mono. Here is the 500 EXC engine.
Box: 2 bits
Powerful compact, lightweight, simple, 2-stroke single cylinder had its glorious off-road hours.
The recent evolution of pollution control standards has disqualified him a little, but he also did not have his last word ... TT pilots who chose valve engines did not necessarily integrate or digest the additional operating costs that would lead to this. More complex engines that run faster, requiring more regular maintenance (valve clearance checks, distribution chain, high wear of titanium valves with dust ...). All this is expensive ... Some are starting to think that finally, cylinders with holes ... It was not so bad!
