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Direct Injection and the Two Stroke

by JohnNicholas on 06/06/2011

Oh no! Not another article about direct injection!

Of all the subjects talked about on the TSM forums, DI is the one that brings out the most emotion.

On one side you have the traditionalists that demand carburetors and on the other those who think DI will save two-strokes. Some even think DI as a technology will destroy the two-stroke.

How could DI create such an uproar?

Ossa DI 2 Stroke

First it would be helpful to understand why DI was talked about in the first place. Plain and simple because of upcoming emission regulations.

Regardless of your political leanings on the subject of emission controls, itís here to stay and will affect our future. Regardless of the reasons for these regulations to be instituted, they will have an effect on new manufacturing of two-strokes (and four-strokes) in the future. This is how the world works.

Polaris 1200 Direct Injection 2 Stroke

So why is DI so high on the list when it comes to lowering emissions on two-strokes? Due to the inherent design of the current two-stroke, which allows a charge of raw fuel to escape through the exhaust pipe. This aspect alone creates the lions share of the emissions measured at the exhaust pipe.

The use of DI  eliminates this one aspect of the ďdirtyĒ two-stroke. Resulting in greatly reduced emissions on two-strokes. Instead of re-hashing the reasons here, take a few moments to read this article;


The EPA regulations state that vehicles manufactured for closed course racing do not have to adhere to these regulations. At first glance this is great news for two-strokes in motocross. That is until you discover that nearly 60% of the motocross bikes sold in the USA are used for recreation and not competition.

When this was brought up during EPA meetings with the manufacturers, there was no easy way to limit sales for competition use only. The move to four-strokes made this task easier in the short term, so thatís what the Big 4 manufacturers chose.

Is DI the savior of two-strokes? Itís difficult to tell the future without a crystal ball. Although from the information presented over the past few years,  indicates the addition of DI could extend the life of two-strokes for a few decades. Unfortunately using the carburetor configuration, only a limited number of machines from select small manufacturers or used machines will be available.

Arctic Cat 900 EFI Two Stroke

If itís a choice between a DI two-stroke and no two-stroke, Iíll choose the DI every time.

DI kit for the Yamaha Banshee