Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
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VOL. 52 ISSUE 3 JANUARY 20, 2015 P119 It's not even true any more. Smoky old-tech two-strokes may indeed have cast visible and odorous palls over the cell- block apartments of the old Eastern Bloc, and perhaps still do in the slums of parts of the Far East. But with modern metallurgy, synthetic oils and direct in- jection, this is no longer the case, as a handful of scooters and the like have been able to demonstrate. Other very prom- ising developments continue, employing supercharging and electronic exhaust controls, with Australia a particular hot- bed. But the two-stroke remains marooned in a backwater. In automotive and by exten- sion motorcycle production, fashion and snobbery are a very powerful force. Bike Grand Prix racing had al- ready played the major role in tak- ing the two-stroke from the realms of cheap lawnmowers and low- grade mopeds to performance levels that drove the prevalent four-strokes into an exile, from which they had to be rescued by imposing new regulations. Most of the credit goes to East German genius Walter Kaaden, who understood that a two-stroke can be made to sing, and that the resonances of that melody can take the place of physical valves. MZ's Stradi- varius of the pit lane turned the two-stroke from a putt-putt into a musical instrument. That was only the start. The Japanese, working with that select group of Western two- stroke gurus, refined the con- cept to increase the vocal range. Race by race reworked cylinders and reshaped exhaust expansion chambers would be tried, some wrapped in asbes- tos to stabilize their heat profile. While on the inlet side, piston ports, rotary valves and reed valves vied for superiority and electronic carburetors took ear- ly steps towards fuel injection. It was a time of rats-tail files, wild-eyed boffins, technicians with split fingernails, and sud- den leaps forward (and some- times backward) in perfor- mance. Proper motorbike stuff. There are better reasons than this to espouse two-strokes, however. Compare a two-stroke cylin- der and head with a four-stroke. The former is a pair of simple alloy castings, with some holes in the bore. It weighs very little, and can be made and modified with relative ease and very few industrial processes. A four-stroke cylinder head and its associated valve gear are a nightmare of complexity by comparison. Different metals, made with exacting precision in belching foundries, subject to a variety of machining and hard- ening processes, whirr round and round and up and down, wearing out as they do so. Should they become deranged, total destruction is inevitable. Worse still is the weight, and where that weight is carried. A two-stroke has nothing above its combustion chamber but air; a four-stroke has two steel camshafts and their gears, cam followers, valves and springs, plus their lubrication. If those springs are pneumatic, then there is a bunch of associated pressure gear. If the operation is desmodromic, it's even more complex. All carried high up, significantly raising an engine's center of gravity. It's a no-brainer to realize that, for a motorcycle especially, a light, simple low C-of-G two- stroke is a much better solution. There are still a handful of the old two-stroke boffins keeping the faith. But they are confined to back rooms, to distant re- search labs, to academia, and at present to irrelevance. We must hope they will prosper again. The murder came at the hands of the industry itself, in the shape of the Honda-led MSMA. Old man Honda hated two-strokes. His influence remained long af- ter his demise. And it carried the industry along with it. We are all the poorer as a re- sult. Even if we don't smell poor. CN