Definition: A "Thumb Throttle" refers to a method of controlling the speed of an engine or motor. A thumb throttle is located on the right side of the handle bar and is a small lever on under side of the handle bar that is operated by pushing inwards with your thumb.
When you push your thumb in you are increasing the engine speed (going faster). When you bring your thumb back towards you (or let go of the throttle and let the springs return it), it slows the engine down.
