Hey guys, I am new to this whole scooter thing, but i am looking for some input on this. My girl and I are taking on refurbishing a early 70's CT90 with a siezed motor for the winter. I am debating what motor we are going to be swapping in there, but for a while now i have had the hankering to put in a Lifan motor with electric start and 12v . My question is, what size motor should i put in there? My initial reaction was to swap in the most powerful plentiful motor via 150,140 or 110cc but lately i have been thinking about a 50cc motor, however it seems counter intuitive to swap in a less powerful or smaller motor. We are in CO and here scoots under 50cc do not need insurance, registration, can ride bike trails and can park on sidewalk. So there are some inherent governmental advantages to having a 50cc mill. I, for one, am skeptical that any LEO's would take the time to read the cc's on the motor. What would you swap in? Sidenote: i have a myriad of other 2 wheeled machines in higher displacements, i am looking to build this little bike as a learning experience for my girlfriend and a good Boulder knock around.