Most modern motor scooters have smaller wheels than
motorcycles, between eight and 12 inches (20-28 cm) in diameter (though maxi-
and big-wheel scooters may have larger wheels). Most scooters have smaller
engines than motorcycles (between 30 cc and 250 cc with a single cylinder,
though larger models have twin cylinder 400 to 650 cc. motors).
Most jurisdictions have no legal definition for "scooter".
Scooters increasingly have four-stroke engines to meet stricter emissions
controls. Trends world-wide have seen new variations on the classic scooter. A
common variation, the 'big-wheel' or commuter-style scooter features wheels as
large as a motorcycle.
High-end scooter models now include comprehensive
technological features including cast aluminum frames, engines with integral
counter-balancing, and cross-linked brake systems.