Just a quick note. Most 50cc scooters require a gas and oil fuel mixture for its two stroke engines and thus don't require an oil change. Most 150 cc scooters have an oil crank case which does require an oil change periodically. 50 ccs usually speed from 2 to 40 MPG. 150 ccs speed up around 60 mph.
I'm buying a 150 cc R9 and the metal placards/signs on it with technical info do not mention if it's a 50 or 150cc. I looked underneath the scooter for the crank cases's drain plug and there it was - it's a 150! It also sped like a bat out of he_ _, way over 35mph - it's a 150!