KTM’s Transfer Port Injection system is so simple in design that the only visible changes to normal two-stroke engine are the fuel-injection hoses going into the transfer ports.

Dear MXA,

Why is MXA so upbeat on fuel-injected two-strokes. In the last year, you have tested four fuel-injected two-strokes, none of which were designed as motocross bikes. To my way of thinking, fuel-injected two-strokes are the antithesis of what two-strokes are all about, which is simplicity, low-cost and fix-it-yourself maintenance.

You are correct. The current carbureted two-stroke is simple, light and relatively inexpensive. Without a doubt, fuel injection will raise the complexity, weight and cost. To tell the truth, KTM and Husqvarna don’t want to build fuel-injected two-strokes. So why do they? Afterall, the American market isn’t demanding this new technology. Their customers are happy with what already exists. The EFI bikes won’t be faster or lighter. And, KTM already owns the two-stroke off-road market with its carbureted bikes. So, why is KTM dumping oodles of dough into developing fuel-injected two-strokes? What are they afraid of?

The 2020 Husqvarna TX300i is an off-road model that uses the same basic chassis and suspension of the KTM 250SX two-stroke motocross bike.

That’s simple. They are afraid of government regulators, like the men who run the EPA in America and Euro5 in Europe. If fuel-injected two-strokes aren’t developed in the coming years, two-strokes could become obsolete. You think it can’t happen, but when was the last time you saw a two-stroke street bike. Emissions standards have been getting stricter with each passing year. In Europe, the restrictive Euro4 legislation went into effect in 2016, and the new Euro5 regulations have even stricter emissions standards. Euro5 is like a gun held to the two-stroke’s head.

Luckily, KTM saw this coming and started developing prototype fuel-injected two-strokes more than a decade ago. Over that decade, KTM tried every possibility for building a fuel-injected two-stroke—and that included direct injection. It wasn’t until they built working prototypes that they realized that direct-injecting a two-stroke required too many compromises, including cylinder height, high fuel-pump pressures and excessive weight. The path to the current Transfer Port Injection (TPI) solution was not smooth, but once they worked out the bugs, the system was clean, simple, light and affordable. With TPI, the KTM engineers were able to carry over the same dimensions and layout as on the carbureted engines. The major changes between a carbureted KTM and a fuel-injected KTM were two lateral domes that hold the nozzles that inject fuel into the cylinder’s transfer ports.

The MXA wrecking crew takes every opportunity to build fuel-injected two-stroke motocross bikes out of KTM and Husky’s EFI off-road models. Why? We need as much experience with the technology as possible—because fuel-injected motocross bikes are on the horizon.

We don’t expect hardcore two-stroke fans to embrace fuel injection, especially as long as their Keihin- and Mikuni-carbureted bikes are still legal, which is exactly what Ford, Chevy and Dodge thought when Honda introduce the 1973 Civic CVCC with its ultra-clean-running Compound Vortex Controlled Combustion engine. When the 1975 Clean Air Act went into effect, Honda was the only manufacturer with an engine that could pass emission standards without a lot of downstream components. KTM doesn’t want to be caught with its pants down, so in 2020, every KTM and Husqvarna offroad two-stroke model will be fuel-injected. At this moment in time, that does not included its motocross models, but as MXA has proven over the last year, fuel-injected motocross bikes are a real possibility.


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