Hi, I am in Pewaukee and Waukesha area. I looked this up quite a bit and I carry the relevant Wisconsin statutes around with me just in case an uninformed cop stops me. The statures are very specific about motorized bicycles and I have never been stopped by cops even going close to 30 mph. And, I really don't think they care if I am going over 30 mph.
The DMV will have little information regarding motorized bicycles because MB are exempt from licensing, registration, and insurance. The state do want you to run headlights if you are riding at night though. The only thing is that a municipality can set their own laws regarding motorized bicycles that supercedes the states, but I checked every municipality around me and they don't have anything specific. I guess just don't cause a ruckus and you should be fine.
I see the Kenosha guy's craiglists as well. The bikes he uses are $80-100 fromWalmart, engine kit probably $120, and probably a few extras that he lists. So, I think there is probably like a $100 premium on top of the raw materials for his service of putting it together. If you just don't want to futz with installing the engine and want a "pro" to do it, then it is a good way to go. Note, he uses cruisers without V or disc brakes so I really figure out if the coaster brakes are good enough before going too fast. Otherwise, find a decent bike with decent brakes, order a kit, and you can enjoy the fun of putting it together.
statute 340.30
(30) "Motor bicycle" means any of the following:
(a) A bicycle to which a power unit not an integral part of the vehicle has been added to permit the vehicle to travel at a speed of not more than 30 miles per hour with a 150-pound rider on a dry, level, hard surface with no wind and having a seat for the operator.
statute 341.05
41.05 When vehicles exempt from registration. A vehicle, even though operated upon a highway of this state, is exempt from registration if any of the following applies:
(23) The vehicle is a motor bicycle or bicycle, except as provided in s. 349.18.