That doesn't mean that your scooter couldn't have one though. I have seen exhaust restrictors in person on a 4 stroke scooter, but both of my 2 strokes were free of exhaust restrictors.
These are usually a washer or other object that allows less air or exhaust to pass by it, thus keeping the engine from 'breathing' properly. Sometimes restrictors limit the engine's power output by placing obstructions in the exhaust or intake manifold. Since many states require 49cc scooters to drive 35MPH or less the restrictors help to keep the average person from pushing much above that speed. Some 49cc scooters are manufactured with restrictors to limit power output and/or top speed.
Here's text from the tech section that I copied and pasted: I believe the word you're looking for is 'restrictions'.
