Starting Problems

Hello everyone... I am new to the group. I just purchased a 1981 Maxim 550 and the bike was running great. The carb was recently worked on and synched and the valves were checked and everything seemed fine. I have put about 100 miles on it since buying it and today I rode it to work and back (about 7 miles each way), stopped at 7 Eleven near my house and shut the bike off. I was only in the store a couple of minutes and when I tried to leave, the bike wouldn't start. The starter spins but the engine doesn't turn over. I pushed it home, cursing all the way, and began trying to troubleshoot. I work on cars some but have never worked on a bike. Given my symptoms, normally on a car or truck I might have a bad starter or a broken timing chain. Either the bendix gear isn't engaging or the chain or belt is broke and thus the engine doesn't turn over. In this case, I assume the setup is a bit different. I removed the starter and it visually seems fine. I energized it and it spins with no problem. The gear just inside the housing where the starter fits was initially a bit loose. Could there be other problems than the starter? What should be my next move? I am assuming something is broken or maybe just loose but I am still getting to know this bike and would like to avoid any unneeded steps. If anyone has any suggestions I would greatly appreciate them.