50cc

From scoot.net

50 cubic centimeters (cc) is a common engine displacement for many scooters on the market. Although many are actually 49cc, it is referred to, and marketed as, a "50cc" for simplicity's sake. Many U.S. states allow 50cc or below scooters to be ridden without a motorcycle endorsement, which adds to their popularity.

Derestriction

Derestricting a 50cc scooter