A 2-stroke, single-cylinder engine has the big advantage of strong, torque-y performance. The air-cooled type used on the DT models also has the advantage of reduced weight and easier servicing, because it doesn't require a liquid-cooling component. A 2-stroke also doesn't require regular oil changes. The DT engines are fitted with the exclusive Yamaha Energy Induction System (YEIS). This unique intake system features a chamber between the carburetor and the reed valve that fills with air-fuel mixture when the reed valve is closed. The chamber's contents are then returned to the air-fuel flow from the carburetor when the reed valve opens. This increases intake efficiency to provide both added power in the low- to mid-speed range and better fuel economy. The strong steel rear carrier has a flat top surface. It is mounted almost on the same level as the rear seat to accommodate a greater variety of loads and loading styles.