It is not that the people who are supposed to answer questions at the Sec of State are incompetent; it's just that if you ask ,they always try to quote parts of the motor vehicle code that deal with the subject you inquired about. So they search for parts about motorized bicycles--and
there aren't any. So they either send you stuff about "motorized pedalcycles", which are
mopeds, or they send you quoted passages about obtaining titles and registering vehicles that have VINs--and that doesn't apply to bicycles at all, either.
If there was a part that said "any vehicles not specified as legal, are prohibited", that would make it easy--but I haven't been able to find anything that says that (as far as I can understand, not being proficient in legalese).
The definition of bicycle they use says "propelled by human power", but it doesn't prohibit engines. And the other parts that mention motorized vehicles and toys that are not street-legal, do not specifically mention motorized bicycles among them.
At the time I started riding mine, a co-worker said there were a couple older guys in his neighborhood (in the same town as me) who had been riding these things around the neighborhood for a number of years.
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Bummer if you are getting hassled. Maybe go riding and let a cop write you a ticket? A first offense can't cost much, you'd get a definite answer one way or the other and the judge might drop the fine totally out of disgust if the Sec of State can't provide a straight answer.
Every roadway law they claim to have should be written in the Motor Vehicle Code. The State's attorney should be able to point out the parts that explain that a motorized bike is prohibited. I've spent quite a while looking, and I cannot find anything that says that.
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