Tic
Simple motor tics are typically sudden, brief, meaningless movements that usually involve only one group of muscles, such as eye blinking, head jerking, or shoulder shrugging. Motor tics can be of an endless variety and may include such movements as hand clapping, neck stretching, mouth movements, head, arm or leg jerks, and facial grimacing.
List of motorcycles by type of engine
The Tandem Twin is where the cylinders are longitudinal, and have two cranks geared together. A tandem twin is effectively a pair of geared singles, and is to be distinguished from an inline twin. Tandem twins are suitable primarily for two-stroke racers.