There’s something magical about a 2 stroke engine. Maybe it’s the high-pitched, metallic scream when you red line it. Or perhaps it’s the wheelie-inducing, lightning fast acceleration you get from first gear. Either way, these engines are genuinely fun. And loud. It makes all kinds of exotic noises. Consider mowing your neighbour’s lawn every once in a while, just so you can sit in your garage and take in the ‘symphony of 7000 rpm’.
Two stroke has been the engine of choice for many manufacturers through the years. In the 50’s, Saab used a 764cc, two-cylinder, two-stroke engine to notch up several rally victories on the Scandinavian stages with the Saab 92.
Its popularity very much evident with the hundreds of spectators that lined up at super specials just to listen to its high revving, throaty exhaust note as it flew over crests and drifted around corners on the gravel surfaces of Finland’s 1000 lakes rally, the drivers keeping the engine on boil throughout the stages.
The Japanese were also heavily inclined towards two strokes. Honda built their empire on small capacity, two-stroke engines, which they fitted on to bicycles. And Suzuki held on to their two-stroke engine as late as 1977. Even our beloved Maruti 800 started life in Japan with a two-stroke, 550cc power plant. And let’s not forget Karl Benz first found success with a two-stroke engine back in 1873.
Two strokes don’t need as much maintenance as four strokes do, since they lack complicated components like valves, cams and timing belts. This makes them simple to work on as well. You could do a minor rebuild sipping tea on a Sunday afternoon, and still have time to spare for a ride.
But here’s the problem. Carbureted two-strokes aren’t particularly fuel efficient. They aren’t exactly environmental friendly either. How many times have you fired up that old Yamaha in a cloud of blue smoke and then imagined hearing Greenpeace activists knocking on your front door? In this day and age of rising fuel prices and going green, two strokes are sticking out worse than a bald man wearing an ill-fitting wig. Is that adrenaline-rush really all that worth it, as you overtake a tree hugging, four stroke?
Two strokes combine intake and exhaust functions in the same stroke. This means a proportion of the fuel/air mixture entering the cylinder goes directly out, unburned, through the exhaust port. Mixing oil into the petrol tank is also common among two strokes. This often clogs the carburetors and things tend to get a bit messy when the one neglects the bike for too long.
In the US, two strokes are already illegal because they don’t comply with emission standards. After immense pressure from the bureaucrats, the manufactures eventually got the message. Four stroke was the way to go. And it’s not long before India will go that way too. What will be the fate of countless RD350 and RX100’s if this were to happen? Destined to scrap yards, museums, private tracks or into the hands of automotive collectors? I really don’t want to think about it.
But don’t worry. If things do happen to go against us hard-core, two-stroke enthusiasts, we can always retire to our garages on a lazy Sunday afternoon, reminiscing about the good old 80’s. Listening to the ring-a-ding-ding orchestra and remembering a time when life was much more exciting and much less stressful. I think it’s time to mow my neighbour’s lawn now.
Aerospace Dynamics 