Honda specifically mentions "motorized bicycles" Since getting interested in them, I have noticed an overwhelming amount of negativity connected with them. Everybody seems to put them down, whether they ride a regular bicycle or not. While they are legal in AZ, up to 48cc, the police will still sometimes harass you about it. The "cycling community" here (I'm talking about the spandex wearing Lance Armstrong types) have been very vocal about them being ridden in bike lanes, which is legal here.
I don't know what the laws are concerning their legality in other states, here you can ride one up to 48cc with no license or insurance. I also own a moped, a real genuine 1977 Puch Maxi, and it is almost completely useless here. It CANNOT be legally ridden in the bike lanes, and with a max speed of 30 mph, it cannot be ridden on the street with other traffic either, because it is too slow. I did used to have a VeloSolex, which is actually a 49cc moped, but looks like a front engined motorized bicycle, with a top speed of 20 mph. I rode it in the bike lanes all the time, and never got hassled about it, other than a few negative comments from the spandex set, but it simply was not sturdy enough to hold up under my weight on the bumpy roads we have here, and I got tired of replacing rear wheels.
I realize that MB building is a hobby, but I wouldn't mind seeing some manufacturer actually build one complete, without all the issues the homebuilt ones have. They could have weld on mounts for everything, no rag joint sprockets or clamp on screen door roller chain tensioners, and they could be built to last. Something like that could be a real form of cheap transportation nationwide. I think a lot of people would ride them, if they were just gas and go, and did not require all the maintenance and tinkering the homebuilt ones do.
Anyway, it seems that installing an engine on a bicycle is not considered acceptable by the vast majority of people in the U.S. I don't have any idea how people in other countries feel about it.
BTW, decided to go friction drive the first time, with a Staton kit and a Robin-Suburu motor. Parts have been ordered. I also ordered a Chinese HT engine gas tank, as a way of carrying some extra fuel, and for looks.