Legal Question in Criminal Law in Michigan

Theorectically ... yes. There is a crime of Larceny By Conversion in which someone gets possession of another person's property legally and then essentially converts it to his own property/use. A simple example could be that you loan your neighbor your lawn mower and then he keeps it and refuses to give it back (and intends to permanently deprive you of it ... which is the essence of a larceny). Like many other crime, this one has several levels, depending on the value of what was stolen: two misdemeanor levels if the value was under $1,000 and two felony levels if the value is $1,000 or more. So, you may want to contact the police to look into this. I hope that you retained some paperwork (like a repair estimate) that proves that you gave the bike to this group so it could be repaired, because a likely "defense story" would be that you sold the bike to them. Also, if you had them do work on your bike and then never paid them for the work, they can put a mechanic's lien on the bike to hold it until you pay them for the work they have done. If so, then they have not "stolen" it because they are not intending on permanently depriving you of it ... they will return it when you pay them for their parts/labor.