A​n Unnecessary & Quite Late Lecture - 2 Stroke Vs. 4 Stroke

M​y thoughts on a discussion that has now long been resolved. In any case, I proceed.

3w ago

The two-stroke engine is different from the four-stroke in several ways. The first and possibly the most easily-recognisable difference is apparent to every Indian and in fact everyone further east who have heard unmuffled Tuk-tuks (what we call autos) rushing up and down their streets - they sound like insects.

The reason the two stroke engine sounds distinctly different from its more advanced counterpart, is that it's doing all the work of a four-stroke engine, using only half the movement of the crankshaft. It’s the reason there are several more explosions within the cylinders in any amount of measured time, when using a two stroke engine. It translates, sounding quite harried and unsophisticated.

The only times I’ve heard fond descriptions of two-stroke engines are when friends are referring to either the Yamaha RX100 (which we can all agree is a bit of a classic at this point) or an old Jawa. Other than that, consensus seems to be against the resilient little thing.

My opinion is that the two-stroke engine doesn’t necessarily need to exist outside of it’s duties as an engine for lawnmowers and leaf-blowers. They’re considerably less easy to maintain for multiple reasons. You require a special mix of fuel and oil for two-stroke engines because lubricating oil is not supplied from within the engine (while four-stroke engines supply lubricant from within the crank-case).

We all know the smell of two-stroke exhaust but can’t really put our finger on the four stroke’s bouquet. The smoke emitted by a two-stroke engine contains plenty of the oil mixed with the fuel as it isn’t fully burnt within the cylinders, rendering it the distinct smell we all remember. The environmentally minded unsurprisingly despise the two-stroke. As you may have realised by now, there is a recurring trend with this engine - it’s lack of sophistication.

However, advantages to the two-stroke should be mentioned. As its piston movement is essentially halved when compared to the four-stroke, full revolutions can be more quickly completed and the engine can therefore be revved significantly higher. This improves acceleration drastically, which is why whenever you do see an old RX on the road, it’s going faster than you (and making its presence felt).

With regard to the four-stroke engine, the very staple of our motoring diet, plenty can be said. It manages the process of intake, compression, ignition, combustion and exhaust with significantly more panache than the two-stroke.

It’s come to take on several forms which have formed entire classes of car. The American V8 for example, is a four-stroke engine that defined the sound of an era. Every time we see a Mach 1 or a classic Fastback, we think V8. The V12 on the other hand formed the sound of an era within Formula 1, which has now passed. We will never forget the high pitched whine that accompanied speeds of above 200 miles an hour on the straight at Circuit de la Sarthe. Even the modern autos manufactured by Bajaj use moderately powered four-strokes to carry their passengers with some level of inconspicuousness. This engine has from the beginning, been the block upon which the greatest manufacturers have built.

M​icah Bedford

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Comments (11)

  • Imagine a two-stroke F1 👀😊

      23 days ago
  • Two strokes just sound broken.

    Part of the reason for all that racket is that half the cylinder bore is missing.

      24 days ago
    • Diesel two stroke engines sound decent though.

        23 days ago
    • Try listening to a two-stroke Tuk-tuk. It sounds broken but more importantly, it is deafening.

        18 days ago
  • Two strokes sound way better! First have you had a go on one? If you are just listening to what other people say and have never even been on a two stroke, stop doing that

    Also, you forgot the most important part- more torque!

      19 days ago
  • The higher revs, harder maintenance stuff is so extremely wrong, i want to bash my head against a wall. Also, if with RX you meant the RX7 and RX8, those aren‘t two strokes, those are wankel engines.

    A two stroke could be rebuilt by any hamfisted beginner because it has considerably less moving parts because anything you‘d find in the cylinderhead of a four-stroke falls away by default. And how high you can rev is determined by the inertia and stroke of your engine combined with maximum mass flow through your head and not „revolutions more easily completed“, whatever that means.

      23 days ago
    • I think he is referring to the Yamaha RXs, such as this 100 2 stroke.

        20 days ago
    • I meant the Yamaha RX100 motorbike. That thing shifts.

        18 days ago
  • Was in Thailand when 2 stroke bikes were being phased out. THe last NSX was a beast. They are becoming collectors items over there now.

    I would rent a CB400 for big trips through the mountains. The big heavy bugger would sigh when we heard a 2 stroke coming up the bends behind us. I think that is why they are so loud. it gives you time to get out of the way and let them fly past.

    I suggest the future will be a massively heavy and silent electric bike getting out of the way for a Duc 996 four stroke.

    I just hope i am on the Duc. Less built in obsolescence with the Duc.

    Have fun

      23 days ago