There are three main types of induction used in 2strokes;(1) piston port where the piston serves as the valve,(2) rotary valve which uses a disc that rotates and (3) Reed valve which is currently the most common these can either be case reed where the intake feeds directly into the case of the engine or cylinder reed such as the blaster. Some common two strokes that don't use reeds are chainsaws and weed eaters, they are usually piston port. An other are the smaller R/C engines which are usually rotary valve, but instead of a disc they use the crankshaft as the rotor.