The two-stroke versus four-stroke dirt bike debate has been going on since at least the 1970s, when lightweight two-strokes dominated every motocross track in the nation. The four-stroke dirt bikes of the time were heavy, cumbersome beasts that simply could not compete with the quick and agile two-strokes. While some of this debate can be chalked up to brand or model loyalty, there are some important differences in the two designs, particularly evident in older models. Modern dirt bike engines of both designs are fairly competitive with one another.
A four-stroke dirt bike uses regular gasoline, while a two-stroke dirt bike requires a mixture of gasoline and two-cycle oil. This might not be an issue on a closed racing track where access to fuel is easy, but you should consider this difference when traveling to remote areas, where fuel availability and type are limited.
Modern four-stroke designs are fairly close to the weight of their two-stroke counterparts, although they are still slightly heavier. The older four-stroke designs, however, are much heavier. This weight limits the capability of the machine and requires more effort to ride quickly. The heavier weight of the four-stroke comes from the extra components, such as a camshaft, timing-chain and other valve-train components that the two-stroke does not have.
Tractable power refers to the ability of the engine to produce power in a smooth fashion that allows the wheels to maintain traction under power. A four-stroke engine has the advantage here. The power from a four-stroke engine is smoother and more controllable under acceleration. The four-stroke design offers more usable low-end pulling power than the two-stroke. This characteristic gives a four-stroke dirt bike the advantage in wet or muddy areas.
A two-stroke can generally accelerate quicker than a four-stroke of the same size. The two-stroke engine builds engine speed more quickly and this translates to quicker ground speed. Because of its design, the two-stroke engine reaches a higher rpm than the four-stroke. This ability to rev more quickly can translate to quicker lap times on a motocross track.
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