Other than parts coming loose before I knew the importance of locktight, the only problem I ever had was the bike not wanting to start after a long hot ride. Turned out it was dielectric grease that had oozed onto my battery terminal and corroded a little. A hex nut tool and a multi-tool were all I needed and I was up and running. Lack everyone has said already, a decent basic tool kit will take care of 90% of the problems.
