“What happened to the two-stroke?” is a question that is often asked but rarely answered without a tinfoil hat on. As usual, the internet has a few answers to that query, citing a bit of conspiracy and a bit of “corporate greed” as we have come to discover from the internet.
While the topic of two strokes can be long-winded and can get quite deep, there are a few sources that point to why four strokes began to dominate on the street and in professional racing circuits.
Two-strokes for the street went away a long time ago. Strict emissions regulations made sure that four strokes became pretty much the only thing that you could get from dealership floors if you wanted a street bike. Eventually, the only other way to get a two-stroke motorcycle between your legs was to go off-road. Brands like KTM are among the only companies out there that still keep a two-stroke motorcycle in their modern lineup but most brands aren’t so keen.
Gallery: KTM EXC 350 and 300 Six Days
There are a couple of reasons why racers and riders love two-stroke motorcycles, which are lightness, simplicity, and power. It takes only a few cubic centimeters of displacement to make a lot of power in a two-stroke. Engines are also simpler to work on, and there’s a lot less complexity. The power delivery from a two-stroke engine is also more manic than a comparable four-stroke, and you’re definitely getting more horsepower per cubic centimeter and even a lighter motor to boot. The emissions thing, however, is a debatable topic since it could have been possible to make two strokes run cleaner, but it would take a lot of R&D money in order to do so.
Four strokes, in comparison, are heavier and more complex to work on. Sure you didn’t have to make a premix of fuel or deal with the smell of burning oil, but if you’re a die-hard two-stroke fan you’ll know the smell and you’re probably hooked. Another benefit of going for the four-stroke is longer intervals between maintenance. Since you burn cleaner, the engine requires less attention. It’s also well-known that four-strokes are cheaper to make clean and fit emissions standards compared to two-strokes, but they’re ultimately going to be more expensive for the consumer with less power for a given displacement as well.
There are even conspiracies surrounding the disappearance of two strokes in the motocross scene with sanctioning bodies giving four strokes a big displacement advantage for four strokes. In the 90s, two-strokes were pitted up against four strokes with nearly double the displacement, 250s against 450s, which MX racers cited as an inaccurate matchup, and one that increased the cost of maintenance and repair for the riders.
Aside from that, it’s mostly a battle of regulations and resources. Governments will regulate pollution, and brands have to comply or they can’t sell. Resources are finite and allocating said resources is a challenge given that engine emissions research and development usually soak up a ton of R&D dollars. If you fancy a deep dive into the topic, we’ve assembled quite a number of sources for you to comb through.
Sources: YouTube - RedBull Motorsports , YouTube - FortNine , Cycle World , Revzilla