Dirt Bikes are designed and built to be ridden off public roads, on rough even mountainous terrain. These dirt bikes feature small engines having less power than larger bikes, long suspension travel as well as high ground clearance, simple construction and minimal body work, no street accessories (such as turn signals and horns), and large wheels with heavy-duty tires for traction, clamped by rim-locks.
The types of dirt bikes are in reference to their engines:
Young Riders: 50cc - 150cc Older or Adult Riders: 250cc, 400cc, and 650cc
Having both air- and water-cooled motor systems, dirt bikes are designed for a variety of purposes, most especially competitive sports (Motorcross, Enduros), time or speed trials, rough terrain traversing, endurance, and fun and recreation.
Trial Bikes
Trial bikes are a particular variation of dirt bike. They are designed for motorcycle trial conditions, and are expected to be pushed to the limit, which is probably one reason they aren't built heavy or sturdy. Typically, this kind of dirt bike is extremely small (up to 250cc engine size and power), and is built considerably light (no seat, and other non-essentials are taken off for light-weight movement).
Dual-Sport Bikes
Dual-sport bikes, or "on-off road bikes," are dirt bikes that have legal access to public roads. These dirt bikes have greater suspension travel and include all necessary public-roadway accessories, such as blinkers, horns, state license plates, fenders, and other essentials. Similar to Enduro bikes, these dirt bikes are sometimes constructed for rough terrain and competitive sports.
Dirt bikes are known as the "wild ones" of the motorcycle-class of vehicles. These dirt bikes require riders who are in control and trained well in riding them in various environments. Young and inexperienced riders should be accompanied by an experienced rider when learning to ride a dirt bike. These monsters are fun and exhilarating, but they are just as dangerous!