well your wrong go look at thisThere really is no definition of a motorized bicycle in Michigan law. Michigan only defines mopeds, low speed vehicles and personal mobility devices. Technically, a gas powered bike could fall under the moped law. A moped is anything with a motor under 50cc with less that 2 brake horse power. A moped has to be registered but they also have to have lights, turn signals, brake lights. You have to have a driver's license.
On the other hand, since a motorized bike cannot be registered without putting all the stuff on it, it kind of falls outside the moped law. Frankly, I don't know any cops (I am a retired cop) that considers a motorized bike a moped and I don't any who would give them a second look unless you were doing something stupid on one.
My advice is that unless you have to ride long distances, get an electric which is more stealthy. If you get decide to get a gas bike, get one that doesn't look like a motorcycle and be discrete when you ride it. In other words don't run old ladies and kids off the sidewalks and bike paths and obey the speed limits. Oh, and don't ride it when you are drunk because they can bust you for DUI.
FYI. A personal mobility device is a Segway.