Every internal combustion engine has to complete two missions— set the conditions to create an explosion and evacuate the byproducts of that explosion in the form of exhaust. Each stroke pushes or pulls a piston attached to a crankshaft, sending power through the transmission and, ultimately, to the drive wheel, which moves the vehicle. The fundamental difference between a two-stroke and a four-stroke engine is the number of strokes it takes to complete the explosion and exhaust sequence, but it’s not the only one. Within this process across both models are several technological dissimilarities.
One potential downside of two-stroke engines is they require gasoline mixed with oil. Not good for the environment, the blue smoke produced by this sort of gas has earned these engines the nickname “smokers.” The upside is a superior power-to-weight ratio compared to four-strokes, better starting in cold temperatures, and freakish and twitchy high-rev power. Due to fewer and less complex moving parts, the head of a two-stroke motor is lighter, cheaper to produce, and more accessible for maintenance by amateur mechanics or those with limited tools.
Four-stroke engines have their own set of advantages and disadvantages. They are more technically complex, expensive to produce, and difficult to work on, raising the barrier to entry for many would-be motocross racers. But they have taken over for a reason: Lower emissions, improved fuel efficiency, and more torque across the lower end of the power band have earned them a reputation on the race track.
