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With 2-stroke engines all but dead, KTM has hung onto the uniquely powerful engine architecture for decades – and they just breathed new life into it by adding fuel-injection and other technology into an all new lineup for 2018. Could this signal a new generation of 2-stroke engines – and could we see them make their way back to the street? That may be in their plans.


In a groundbreaking press release last week, KTM announced that they will be releasing an all-new line of fuel-injected 2-stroke enduro machines as 2018 models, to be debuted at an official launch this May.

Yes, you read that right: fuel-injected 2-stroke motorcycles, going into production this year. And yes, at least one model will be coming to U.S. shores.

Specifically, KTM will be rolling out three new fuel-injected 2-stroke machines: the 250 EXC TPI and 300 EXC TPI for the global market, and the 250 XC-W TPI for North America. In addition to utilizing fuel injection in 2-stroke engines – a first for any large-scale manufacturer – KTM is also introducing a unique oil-injection system that eliminates the need to pre-mix fuel. These advancements will modernize the light and powerful 2-stroke platform, making it more powerful, user-friendly, and cleaner-burning than ever. To call these developments from KTM “revolutionary” is not an understatement – in fact, we could be seeing the beginning of an entirely new segment of the industry being born.


A shot of the 2015 KTM EXC 300, with a potent 2-stroke engine. The new KTM 2-strokes will be similar, but with a highly efficient fuel-injected two-stroke – and it may even be street legal.


Actually, re-born would be the more accurate term, as 2-stroke engines have been around for a while, and are actually in many ways superior to their four-stroke counterparts. Because 2-stroke engines combust a cylinder full of air-fuel mixture on every cycle of the piston, rather than on every other cycle like a four-stroke motor does, they produce much more power for a given engine size in a shorter amount of time. In addition, the simplicity of a 2-stroke – since it has no valves or valvetrain to weigh it down – means it is much easier to maintain than the heavier, more complicated, and relatively less powerful four-stroke counterpart. In many applications, particularly in motocross and enduro racing, the 2-stroke engine architecture is ideal.

So if the 2-stroke engine is so awesome – why did it ever go away? In a single word: emissions. 2-stroke engines tend to leave a lot of unburnt fuel in their exhaust gases, and because they burn an oil and gas mixture (pre-mixed before it’s even put into the tank), they emit a constant plume of blue smoke from the burning of oil in the combustion chamber, earning 2-stroke engines the nickname “smokers.”

A leaked schematic of the KTM’s new fuel-injected 2T engine.


The lack of fuel efficiency and constant smoking certainly doesn’t bother racers and gearheads – in fact, they are a distinct part of the 2-stroke charm – but it did bother the EPA and other air qualify management bodies around the world, who began to crack down on emissions restrictions throughout the 1980s and 1990s. Cleaner-burning, more fuel-efficient four-strokes polluted far less and required far less maintenance, and became the standard for street engines, while lighter, more powerful 2-strokes, despite their higher maintenance requirements, became the prime choice of off-road riders and racers.

That would likely still be the case today, if it weren’t for the 1998 ruling of the AMA, the largest motorcycle race sanctioning body in the U.S., to allow heavier, less powerful 450cc four-strokes to compete in the same classes as 250cc 2-strokes. Many say this was from pressure from the manufacturers themselves, who were already spending vast sums of money to develop their four-stroke engines for street uses, and wanted to consolidate R&D into one direction they knew the EPA was unlikely to harass them any further for. That ruling was the death knell of the 2-stroke as a significant segment of the motorcycle market, and within only 5 or 6 years, the 2-stroke had all but died off, carried on only by KTM and a small number of boutique manufacturers.

So the question is, if the 2-stroke engine has all but died off, why is KTM choosing to make such significant advancements in the architecture now? There could be several reasons. One is that, utilizing fuel injection, a 2-stroke could be tuned to run dramatically cleaner than a typical carbureted version, allowing a rider to get the performance and acceleration of a 2-stroke while still remaining emissions legal – which of course is a performance advantage. Another possible factor is Europe’s tiered licensing system, which restricts riders to certain displacement and power limits until they have been riding for a certain number of years – a two stroke could maximize performance while staying within those limits, giving riders a sportier option in those more restricted markets.


While every other major manufacturer backed out of 2-stroke engines years ago, KTM kept developing the unique engine architecture, putting it into modern off-road bikes like this Freeride 250. By adding fuel injection and other technologies to it, KTM may be introducing a whole new chapter to the 2-stroke story.


This is not to say that these three new KTM 2-strokes will be street-legal, because there is no indication that they are (yet.) However, note that KTM decided to release these in an Enduro configuration – a category that, in Europe, must remain road-legal even in racing guise – as opposed to a motocross configuration, which is off-road only. It’s a minor difference in nomenclature, but it could have big implications. With these major advancements in this unique engine architecture, all but abandoned by every other manufacturer, it looks like KTM may be setting themselvess up for a return to the street-legal market with emissions-friendly, street-legal 2-strokes – which, after a decades-long hiatus, would be a fun, powerful, and fascinating type of machine that would likely be welcomed with open arms to today’s market!

Would you be interested in a new KTM 2-stroke 250cc enduro? What about an emissions-legal KTM 2-stroke street bike?

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